Incorporating and interpreting regulatory guidance on estimands in diabetes clinical trials: The PIONEER 1 randomized clinical trial as an example.

Regulatory guidelines describe the use of estimands in designing and conducting clinical trials. Estimands ensure alignment of the objectives with the design, conduct and analysis of a trial. An estimand is defined by four inter-related attributes: the population of interest, the variable (endpoint) of interest, the way intercurrent events are handled and the population level summary. A trial may employ multiple estimands to evaluate treatment effects from different perspectives in order to address different scientific questions. As estimands may be an unfamiliar concept for many clinicians treating diabetes, this paper reviews the estimand concept and uses the PIONEER 1 phase 3a clinical trial, which investigated the efficacy and safety of oral semaglutide vs placebo, as an example of the way in which estimands can be implemented and interpreted. In the PIONEER 1 trial, two estimands were employed for each efficacy endpoint and were labelled as: (a) the treatment policy estimand, used to assess the treatment effect regardless of use of rescue medication or discontinuation of trial product, and provides a broad perspective of the treatment effect in the population of patients with type 2 diabetes in clinical practice; and (b) the trial product estimand, used to assess the treatment effect if all patients had continued to use trial product for the planned duration of the trial without rescue medication, thereby providing information on the anticipated treatment effect of the medication. Both approaches are complementary to understanding the effect of the studied treatments.

GREATER COMBINED REDUCTIONS IN HbA1C ≥1.0% AND WEIGHT ≥5.0% WITH SEMAGLUTIDE VERSUS COMPARATORS IN TYPE 2 DIABETES.

Objective: Semaglutide is a glucagon-like peptide 1 (GLP-1) analog for the once-weekly treatment of type 2 diabetes (T2D). In the global SUSTAIN clinical trial program, semaglutide demonstrated superior glycated hemoglobin (HbA1c) and body weight reductions versus comparators. This post hoc analysis compared the proportion of patients achieving combined reductions in glycemia and body weight versus comparators. Methods: A total of 5,119 subjects with T2D in the phase 3 SUSTAIN 1 through 5 and 7 trials, from 33 countries, were included in this post hoc analysis. Subjects received subcutaneous semaglutide 0.5 or 1.0 mg, placebo or active comparator (sitagliptin 100 mg, exenatide extended release 2.0 mg, insulin glargine, dulaglutide 0.75 or 1.5 mg). The main endpoint was a composite of ≥1.0% HbA1c reduction and ≥5.0% weight loss at end of treatment. Results: Significantly greater proportions of subjects achieved the composite endpoint with semaglutide 0.5 (25 to 38%) and 1.0 mg (38 to 59%) versus comparators (2 to 23%). More subjects treated with semaglutide versus comparators achieved ≥1.0% HbA1c reductions (58 to 77% and 75 to 83% for semaglutide 0.5 and 1.0 mg versus 12 to 68%) and ≥5.0% weight loss (37 to 46%, 45 to 66% versus 4 to 30%). Proportions of subjects achieving targets were significantly higher with semaglutide 1.0 versus 0.5 mg in four of five trials. Semaglutide was well tolerated, with a safety profile similar to other GLP-1 receptor agonists. Conclusion: Significantly more subjects achieved both ≥1.0% HbA1c reduction and ≥5.0% weight loss with once-weekly subcutaneous semaglutide treatment versus comparators in the SUSTAIN trials. A dose-dependent effect was observed with semaglutide. Abbreviations: AE = adverse event; CV = cardiovascular; ER = extended release; GLP-1 = glucagon-like peptide 1; GLP-1 RA = glucagon-like peptide 1 receptor agonist; HbA1c = glycated hemoglobin; OAD = oral antidiabetic drug; sc = subcutaneous; T2D = type 2 diabetes.

A 26-Week Randomized Controlled Trial of Semaglutide Once Daily Versus Liraglutide and Placebo in Patients With Type 2 Diabetes Suboptimally Controlled on Diet and Exercise With or Without Metformin.

OBJECTIVE: To investigate the efficacy and safety of once-daily semaglutide in comparison with once-daily liraglutide and placebo in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: This 26-week, multicenter, double-blind trial involved patients diagnosed with type 2 diabetes with HbA1c 7.0-10.0% (53-86 mmol/mol) and treated with diet and exercise with or without metformin. Patients were randomized 2:2:1 to once-daily semaglutide, liraglutide, or placebo in one of four volume-matched doses (semaglutide 0.05, 0.1, 0.2, or 0.3 mg and liraglutide 0.3, 0.6, 1.2, or 1.8 mg, with both compared within each volume-matched dose group). Primary end point was change in HbA1c from baseline to week 26. RESULTS: In total, 705 randomized patients were exposed to trial products. At week 26, a dose-dependent change in HbA1c was observed with semaglutide from -1.1% (0.05 mg) to -1.9% (0.3 mg) and with liraglutide from -0.5% (0.3 mg) to -1.3% (1.8 mg) (all P < 0.001 in favor of volume-matched semaglutide dose). Change with pooled placebo was -0.02% (P < 0.0001 vs. semaglutide). Gastrointestinal (GI) disorders were the most common adverse events (AEs) with semaglutide and liraglutide, occurring in 32.8-54.0% and 21.9-41.5% of patients, respectively. CONCLUSIONS: Once-daily semaglutide at doses up to 0.3 mg/day resulted in greater reductions in HbA1c compared with liraglutide or placebo but with a higher frequency of GI AEs.

Semaglutide s.c. Once-Weekly in Type 2 Diabetes: A Population Pharmacokinetic Analysis.

INTRODUCTION: Semaglutide, a new treatment option approved for the treatment of patients with type 2 diabetes mellitus, is a glucagon-like peptide-1 receptor agonist to be injected subcutaneously once weekly. This analysis used a population pharmacokinetic model of semaglutide to identify clinically relevant covariates for exposure. METHODS: A total of 1612 patients with up to seven pharmacokinetic observations each were included in the analysis. All subjects had type 2 diabetes mellitus and were enrolled in one of five trials in the phase III development program for subcutaneous semaglutide once weekly (the SUSTAIN program). The treatment duration of the trials varied from 30 to 104 weeks. RESULTS: No clinically relevant effects on the exposure were seen for sex, age, race, ethnicity, renal function, or injection site used, and semaglutide exposure was stable over time. Of the covariates chosen, only body weight had a relevant effect on the exposure of semaglutide. Few subjects developed semaglutide antibodies, and the antibodies had no effect on exposure. Dose proportionality was shown for the 0.5 mg and 1.0 mg maintenance doses of semaglutide. CONCLUSION: The population pharmacokinetic study showed that semaglutide exposure is not affected by covariates other than body weight at either a maintenance dose of 0.5 or 1.0 mg semaglutide. Therefore, we conclude that no semaglutide dose adjustments are needed in different populations. This finding is to be further explored in an exposure-response analysis. TRIAL REGISTRATION: The trials were registered at ClinicalTrials.gov (identifiers: NCT02054897, NCT01930188, NCT01885208, NCT01720446 and NCT02207374). FUNDING: Novo Nordisk A/S, Bagsværd, Denmark.

Achieving glycaemic control without weight gain, hypoglycaemia, or gastrointestinal adverse events in type 2 diabetes in the SUSTAIN clinical trial programme.

AIM: To evaluate the potential for semaglutide to help people with type 2 diabetes (T2D) achieve glycated haemoglobin (HbA1c) targets while avoiding unwanted outcomes, such as weight gain, hypoglycaemia and gastrointestinal (GI) side effects. MATERIALS AND METHODS: Data from the phase IIIa SUSTAIN 1 to 5 clinical trials were analysed. Participants had inadequately controlled T2D and were drug-naïve (SUSTAIN 1) or on a range of background treatments (SUSTAIN 2 to 5). The main protocol-specified composite endpoint was the proportion of participants achieving HbA1c <53 mmol/mol (7.0%) at end of treatment (30 or 56 weeks) without weight gain and with no severe or blood glucose (BG)-confirmed symptomatic hypoglycaemia. A post hoc composite endpoint was the proportion of participants achieving the primary composite endpoint without moderate or severe GI adverse events (AEs). RESULTS: Across the SUSTAIN trials 1 to 5, 3918 participants with T2D were randomized to once-weekly subcutaneous semaglutide 0.5 mg, 1.0 mg, or comparators (placebo, sitagliptin 100 mg, exenatide extended release 2.0 mg or insulin glargine). The proportion of participants achieving HbA1c <53 mmol/mol (7.0%) with no weight gain and no severe/BG-confirmed symptomatic hypoglycaemia was 47% to 66% (semaglutide 0.5 mg) and 57% to 74% (semaglutide 1.0 mg) vs 7% to 19% (placebo) and 16% to 29% (active comparators; all P < .0001). More participants achieved the primary composite endpoint with no moderate or severe GI AEs with semaglutide vs comparators (all P < .0001). CONCLUSION: Semaglutide helped more people with T2D achieve HbA1c targets than did comparators in the SUSTAIN 1 to 5 trials, while avoiding unwanted outcomes such as weight gain, hypoglycaemia and GI side effects.

Exposure-response analysis for evaluation of semaglutide dose levels in type 2 diabetes.

AIMS: To evaluate dose levels for semaglutide, a glucagon-like peptide-1 analogue approved for the treatment of type 2 diabetes, by examining the effects of demographic factors on efficacy and safety in an exposure-response analysis. METHODS: We analysed data from 1552 adults from four randomized phase III trials of 30 to 56 weeks' duration, investigating once-weekly semaglutide doses 0.5 and 1.0 mg. Exposure-response relationships were investigated using graphical and model-based techniques to assess the two dose levels and subgroups with the highest and lowest exposure and response. RESULTS: The population had the following demographic characteristics: baseline mean age between 53.2 and 58.4 years, glycated haemoglobin (HbA1c) between 64 and 67 mmol/mol (8.0% and 8.3%), body weight between 71.3 and 96.2 kg, and diabetes duration between 4.2 and 8.9 years. Exposure-response analysis showed a clear HbA1c and weight reduction across exposures after 30 weeks, irrespective of baseline values. The exposure-response for HbA1c was influenced by baseline HbA1c, and body weight exposure-response was influenced by sex, with limited impact of other factors. Analyses for relevant subgroups of baseline body weight, baseline HbA1c and sex indicated clinically relevant additional benefits with regard to HbA1c and weight with 1.0 vs 0.5 mg semaglutide. The proportion of participants reporting gastrointestinal (GI) side effects increased with increasing exposure, but was counteracted by tolerance development. CONCLUSIONS: The analysis showed that all subgroups obtained a clinically relevant benefit with semaglutide 0.5 mg and an additional benefit with semaglutide 1.0 mg. The increase in GI side effects with higher exposure was mitigated by gradually increasing the dose.

A Randomized Trial Investigating the Pharmacokinetics, Pharmacodynamics, and Safety of Subcutaneous Semaglutide Once-Weekly in Healthy Male Japanese and Caucasian Subjects.

INTRODUCTION: Semaglutide is a glucagon-like peptide-1 analogue for once-weekly subcutaneous treatment of type 2 diabetes. This trial compared the pharmacokinetics, pharmacodynamics, and safety of semaglutide in Japanese and Caucasian subjects. METHODS: In this single-center, double-blind, parallel-group, 13-week trial, 44 healthy male subjects (22 Japanese, 22 Caucasian) were randomized within each race to semaglutide 0.5 mg (n = 8), 1.0 mg (n = 8), placebo 0.5 mg (n = 3) or 1.0 mg (n = 3). The primary endpoint was semaglutide exposure at steady state [area under the curve (AUC0-168h)]. RESULTS: Steady-state exposure of semaglutide was similar for both populations: AUC0-168h estimated race ratio (ERR), Japanese/Caucasian: 0.5 mg, 1.06; 1.0 mg, 0.99; maximum concentration (Cmax) ERR: 0.5 mg, 1.06; 1.0 mg, 1.02. Exposure after the first dose (0.25 mg) was slightly higher in Japanese versus Caucasian subjects (AUC0-168h ERR 1.11; Cmax ERR 1.14). Dose-dependent increases in AUC0-168h and Cmax occurred in both populations. Accumulation was as expected, based on the half-life (t1/2, ~ 1 week) and dosing interval of semaglutide. Significant body weight reductions were observed with semaglutide 0.5 mg and 1.0 mg in Japanese (both p ≤ 0.05) and Caucasian (both p ≤ 0.05) subjects versus placebo. No new safety issues were identified. CONCLUSIONS: The pharmacokinetic, pharmacodynamic, and safety profiles of semaglutide were similar in Japanese and Caucasian subjects, suggesting that no dose adjustment is required for the clinical use of semaglutide in Japanese subjects. FUNDING: Novo Nordisk A/S, Denmark. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT02146079. Japanese trial registration number JapicCTI-142550.

Safety and efficacy of once-weekly semaglutide vs additional oral antidiabetic drugs in Japanese people with inadequately controlled type 2 diabetes: A randomized trial.

AIM: To evaluate the safety and efficacy of once-weekly subcutaneous semaglutide as monotherapy or combined with an oral antidiabetic drug (OAD) vs an additional OAD added to background therapy in Japanese people with type 2 diabetes (T2D) inadequately controlled on diet/exercise or OAD monotherapy. METHODS: In this phase III, open-label trial, adults with T2D were randomized 2:2:1 to semaglutide 0.5 mg or 1.0 mg, or one additional OAD (a dipeptidyl peptidase-4 inhibitor, biguanide, sulphonylurea, glinide, α-glucosidase inhibitor or thiazolidinedione) with a different mode of action from that of background therapy. The primary endpoint was number of adverse events (AEs) after 56 weeks. RESULTS: Baseline characteristics were balanced between treatment arms (601 randomized). More AEs were reported in the semaglutide 0.5 mg (86.2%) and 1.0 mg (88.0%) groups than in the additional OAD group (71.7%). These were typically mild/moderate. Gastrointestinal AEs were most frequent with semaglutide, which diminished over time. The mean glycated haemoglobin (HbA1c) concentration (baseline 8.1%) was significantly reduced with semaglutide 0.5 mg and 1.0 mg vs additional OAD (1.7% and 2.0% vs 0.7%, respectively; estimated treatment difference [ETD] vs additional OAD -1.08% and -1.37%, both P < .0001). Body weight (baseline 71.5 kg) was reduced by 1.4 kg and 3.2 kg with semaglutide 0.5 mg and 1.0 mg, vs a 0.4-kg increase with additional OAD (ETD -1.84 kg and -3.59 kg; both P < .0001). For semaglutide-treated participants, >80% achieved an HbA1c concentration <7.0% (Japanese Diabetes Society target). CONCLUSIONS: Semaglutide was well tolerated, with no new safety issues identified. Semaglutide treatment significantly reduced HbA1c and body weight vs additional OAD treatment in Japanese people with T2D.

Safety and efficacy of semaglutide once weekly vs sitagliptin once daily, both as monotherapy in Japanese people with type 2 diabetes.

AIMS: To assess the safety and efficacy of monotherapy with once-weekly subcutaneous (s.c.) semaglutide vs sitagliptin in Japanese people with type 2 diabetes (T2D). METHODS: In this phase IIIa randomized, open-label, parallel-group, active-controlled, multicentre trial, Japanese adults with T2D treated with diet and exercise only or oral antidiabetic drug monotherapy (washed out during the run-in period) received once-weekly s.c. semaglutide (0.5 or 1.0 mg) or once-daily oral sitagliptin 100 mg. The primary endpoint was number of treatment-emergent adverse events (TEAEs) after 30 weeks. RESULTS: Overall, 308 participants were randomized and exposed to treatment, with similar baseline characteristics across the groups. In total, 2.9% of participants in both the semaglutide 0.5 mg and the sitagliptin group prematurely discontinued treatment, compared with 14.7% in the semaglutide 1.0 mg group. The majority of discontinuations in the semaglutide 0.5 and 1.0 mg groups were attributable to adverse events (AEs). More TEAEs were reported in semaglutide- vs sitagliptin-treated participants (74.8%, 71.6% and 66.0% in the semaglutide 0.5 mg, semaglutide 1.0 mg and sitagliptin groups, respectively). AEs were mainly mild to moderate. Gastrointestinal AEs, most frequently reported with semaglutide, diminished in frequency over time. The mean glycated haemoglobin (HbA1c [baseline 8.1%]) decreased by 1.9% and 2.2% with semaglutide 0.5 and 1.0 mg, respectively, vs 0.7% with sitagliptin (estimated treatment difference [ETD] vs sitagliptin -1.13%, 95% confidence interval [CI] -1.32; -0.94, and -1.44%, 95% CI -1.63; -1.24; both P < .0001). Body weight (baseline 69.3 kg) was reduced by 2.2 and 3.9 kg with semaglutide 0.5 and 1.0 mg, respectively (ETD -2.22 kg, 95% CI -3.02; -1.42 and -3.88 kg, 95% CI -4.70; -3.07; both P < .0001). CONCLUSIONS: In Japanese people with T2D, more TEAEs were reported with semaglutide than with sitagliptin; however, the semaglutide safety profile was similar to that of other glucagon-like peptide-1 receptor agonists. Semaglutide significantly reduced HbA1c and body weight compared with sitagliptin.

Insulin degludec/insulin aspart vs biphasic insulin aspart 30 twice daily in Japanese patients with type 2 diabetes: A randomized controlled trial.

AIMS/INTRODUCTION: Insulin degludec/insulin aspart (IDegAsp) is a soluble combination of insulin degludec (70%) and insulin aspart (30%). The present exploratory trial investigated the safety of switching unit-to-unit from twice-daily basal or pre-mix insulin to twice-daily IDegAsp in Japanese patients with type 2 diabetes. MATERIALS AND METHODS: In this 6-week, open-label, parallel-group, controlled trial, 66 participants were randomized (1:1) to receive either IDegAsp or biphasic insulin aspart 30 (BIAsp 30) twice daily at the same total daily dose as pre-trial insulin. During the trial, insulin doses were adjusted according to a pre-specified algorithm to achieve pre-breakfast and pre-dinner plasma glucose of 4.4-7.2 mmol/L. RESULTS: No severe hypoglycemic episodes occurred. There were no statistically significant differences in rates of confirmed hypoglycemia (rate ratio IDegAsp/BIAsp 30: 0.63, 95% confidence interval: 0.31-1.30) and confirmed nocturnal hypoglycemia (rate ratio: 0.49, 95% confidence interval: 0.10-2.38) for IDegAsp vs BIAsp 30. The hypoglycemia rate for IDegAsp was constant over the 6 weeks of treatment. IDegAsp and BIAsp 30 were both safe and well tolerated. Reduction in fasting plasma glucose was statistically significantly greater for IDegAsp than for BIAsp 30 (estimated treatment difference, IDegAsp-BIAsp 30: -1.6 mmol/L, 95% confidence interval: -2.4 to -0.8). The apparent decrease in mean postprandial plasma glucose increment (IDegAsp: 4.2-3.8 mmol/L; BIAsp 30: 4.5-2.8 mmol/L) was not statistically significantly different between treatments (estimated treatment difference: 1.0 mmol/L, 95% confidence interval: -0.1 to 2.2). CONCLUSIONS: Switching unit-to-unit from basal or pre-mix insulin to IDegAsp seems not to be associated with any concerns related to hypoglycemia or general safety in Japanese patients with type 2 diabetes.

Increased Baseline C-Reactive Protein Concentrations Are Associated with Increased Risk of Infections: Results from 2 Large Danish Population Cohorts.

BACKGROUND: The acute-phase reactant C-reactive protein (CRP) increases rapidly during an infection. We tested the hypothesis that chronic low-level increases in CRP are associated with an increased risk of infectious disease. METHODS: We studied 9660 individuals from a prospective general population cohort, including 3592 in whom infectious disease developed, and another 60 896 individuals from a cross-sectional general population study, of whom 13 332 developed infectious disease; 55% were women, and the mean age was 57 years. Hospital diagnoses of infections in 1977-2010 were based on International Classification of Diseases-coded discharge records from the national Danish Patient Registry. We measured CRP concentrations and conducted genotyping for 4 CRP polymorphisms that increase CRP. Individuals with CRP >10 mg/L were excluded because of possible ongoing infection at the time of testing. RESULTS: Individuals with CRP >3 mg/L had 1.2 and 1.7 times increased risk of infectious disease, in the prospective general population cohort and the cross-sectional general population study, respectively, compared with individuals with CRP <1 mg/L. In the combined populations, individuals in the highest CRP tertile (compared with the lowest) had an increased risk of bacterial diseases (hazard ratio 1.7, 95% CI 1.6-1.8), but not viral, mycosis, and parasitic diseases. The increased risk was mainly carried by pneumonia, sepsis, and particularly gram-negative infections. None of the genotype combinations examined conferred an increased risk of infectious disease. CONCLUSIONS: Chronic low-level CRP increases were associated with increased risk of bacterial infections, gram-negative infections in particular. Genotypes associated with increases in CRP were not associated with increased risk of infection.

Risk of venous thromboembolism associated with single and combined effects of Factor V Leiden, Prothrombin 20210A and Methylenetethraydrofolate reductase C677T: a meta-analysis involving over 11,000 cases and 21,000 controls.

Genetic and environmental factors interact in determining the risk of venous thromboembolism (VTE). The risk associated with the polymorphic variants G1691A of factor V (Factor V Leiden, FVL), G20210A of prothrombin (PT20210A) and C677T of methylentetrahydrofolate reductase (C677T MTHFR) genes has been investigated in many studies. We performed a pooled analysis of case-control and cohort studies investigating in adults the association between each variant and VTE, published on Pubmed, Embase or Google through January 2010. Authors of eligible papers, were invited to provide all available individual data for the pooling. The Odds Ratio (OR) for first VTE associated with each variant, individually and combined with the others, were calculated with a random effect model, in heterozygotes and homozygotes (dominant model for FVL and PT20210A; recessive for C677T MTHFR). We analysed 31 databases, including 11,239 cases and 21,521 controls. No significant association with VTE was found for homozygous C677T MTHFR (OR: 1.38; 95 % confidence intervals [CI]: 0.98-1.93), whereas the risk was increased in carriers of either heterozygous FVL or PT20210 (OR = 4.22; 95 % CI: 3.35-5.32; and OR = 2.79;95 % CI: 2.25-3.46, respectively), in double heterozygotes (OR = 3.42; 95 %CI 1.64-7.13), and in homozygous FVL or PT20210A (OR = 11.45; 95 %CI: 6.79-19.29; and OR: 6.74 (CI 95 % 2.19-20.72), respectively). The stratified analyses showed a stronger effect of FVL on individuals ≤ 45 years (p value for interaction = 0.036) and of PT20210A in women using oral contraceptives (p-value for interaction = 0.045). In this large pooled analysis, inclusive of large studies like MEGA, no effect was found for C677T MTHFR on VTE; FVL and PT20210A were confirmed to be moderate risk factors. Notably, double carriers of the two genetic variants produced an impact on VTE risk significantly increased but weaker than previously thought.

The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach.

BACKGROUND: Adiposity, assessed as elevated body mass index (BMI), is associated with increased risk of ischemic heart disease (IHD); however, whether this is causal is unknown. We tested the hypothesis that positive observational associations between BMI and IHD are causal. METHODS AND FINDINGS: In 75,627 individuals taken from two population-based and one case-control study in Copenhagen, we measured BMI, ascertained 11,056 IHD events, and genotyped FTO(rs9939609), MC4R(rs17782313), and TMEM18(rs6548238). Using genotypes as a combined allele score in instrumental variable analyses, the causal odds ratio (OR) between BMI and IHD was estimated and compared with observational estimates. The allele score-BMI and the allele score-IHD associations used to estimate the causal OR were also calculated individually. In observational analyses the OR for IHD was 1.26 (95% CI 1.19-1.34) for every 4 kg/m(2) increase in BMI. A one-unit allele score increase associated with a 0.28 kg/m(2) (95 CI% 0.20-0.36) increase in BMI and an OR for IHD of 1.03 (95% CI 1.01-1.05) (corresponding to an average 1.68 kg/m(2) BMI increase and 18% increase in the odds of IHD for those carrying all six BMI increasing alleles). In instrumental variable analysis using the same allele score the causal IHD OR for a 4 kg/m(2) increase in BMI was 1.52 (95% CI 1.12-2.05). CONCLUSIONS: For every 4 kg/m(2) increase in BMI, observational estimates suggested a 26% increase in odds for IHD while causal estimates suggested a 52% increase. These data add evidence to support a causal link between increased BMI and IHD risk, though the mechanism may ultimately be through intermediate factors like hypertension, dyslipidemia, and type 2 diabetes. This work has important policy implications for public health, given the continuous nature of the BMI-IHD association and the modifiable nature of BMI. This analysis demonstrates the value of observational studies and their ability to provide unbiased results through inclusion of genetic data avoiding confounding, reverse causation, and bias.

Effect modification by population dietary folate on the association between MTHFR genotype, homocysteine, and stroke risk: a meta-analysis of genetic studies and randomised trials.

BACKGROUND: The MTHFR 677C→T polymorphism has been associated with raised homocysteine concentration and increased risk of stroke. A previous overview showed that the effects were greatest in regions with low dietary folate consumption, but differentiation between the effect of folate and small-study bias was difficult. A meta-analysis of randomised trials of homocysteine-lowering interventions showed no reduction in coronary heart disease events or stroke, but the trials were generally set in populations with high folate consumption. We aimed to reduce the effect of small-study bias and investigate whether folate status modifies the association between MTHFR 677C→T and stroke in a genetic analysis and meta-analysis of randomised controlled trials. METHODS: We established a collaboration of genetic studies consisting of 237 datasets including 59,995 individuals with data for homocysteine and 20,885 stroke events. We compared the genetic findings with a meta-analysis of 13 randomised trials of homocysteine-lowering treatments and stroke risk (45,549 individuals, 2314 stroke events, 269 transient ischaemic attacks). FINDINGS: The effect of the MTHFR 677C→T variant on homocysteine concentration was larger in low folate regions (Asia; difference between individuals with TT versus CC genotype, 3·12 µmol/L, 95% CI 2·23 to 4·01) than in areas with folate fortification (America, Australia, and New Zealand, high; 0·13 µmol/L, -0·85 to 1·11). The odds ratio (OR) for stroke was also higher in Asia (1·68, 95% CI 1·44 to 1·97) than in America, Australia, and New Zealand, high (1·03, 0·84 to 1·25). Most randomised trials took place in regions with high or increasing population folate concentrations. The summary relative risk (RR) of stroke in trials of homocysteine-lowering interventions (0·94, 95% CI 0·85 to 1·04) was similar to that predicted for the same extent of homocysteine reduction in large genetic studies in populations with similar folate status (predicted RR 1·00, 95% CI 0·90 to 1·11). Although the predicted effect of homocysteine reduction from large genetic studies in low folate regions (Asia) was larger (RR 0·78, 95% CI 0·68 to 0·90), no trial has evaluated the effect of lowering of homocysteine on stroke risk exclusively in a low folate region. INTERPRETATION: In regions with increasing levels or established policies of population folate supplementation, evidence from genetic studies and randomised trials is concordant in suggesting an absence of benefit from lowering of homocysteine for prevention of stroke. Further large-scale genetic studies of the association between MTHFR 677C→T and stroke in low folate settings are needed to distinguish effect modification by folate from small-study bias. If future randomised trials of homocysteine-lowering interventions for stroke prevention are undertaken, they should take place in regions with low folate consumption. FUNDING: Full funding sources listed at end of paper (see Acknowledgments).

Using genetic loci to understand the relationship between adiposity and psychological distress: a Mendelian Randomization study in the Copenhagen General Population Study of 53,221 adults.

OBJECTIVE: We used genetic variants that are robustly associated with adiposity to examine the causal association of adiposity with psychological distress. METHODS: We examined the association of adiposity with psychological distress in a large (N = 53,221) general population cohort of 20- to 99-year-old adults from Copenhagen, Denmark. Psychological distress was assessed using four questions that asked about: feeling stressed; not accomplishing very much; wanting to give up; and regular use of antidepressants/sedatives. We used the genetic loci FTO rs9939609 and MC4R rs17782313 as instrumental variables for adiposity quantified by body mass index (BMI) and waist to hip ratio (WHR). RESULTS: In conventional multivariable analyses, BMI and WHR were positively associated with distress. For example, the odds ratio of reporting not accomplishing for each additional standard deviation increase for BMI was 1.11 (95% CI: 1.09, 1.13) and for WHR was 1.10 (95% CI: 1.08, 1.13) in the fully adjusted analyses. In contrast, instrumental variable analyses showed an inverse association of adiposity on distress; corresponding odds ratio in instrumental variable analyses was 0.64 (95% CI: 0.46, 0.89) for BMI and 0.49 (95% CI: 0.25, 0.94) for WHR (P-values for difference between the two approaches both = 0.001). CONCLUSION: The inverse associations of adiposity and psychological distress when genetic variants are used as instrumental variables could be explained by biological pathways linking adiposity and distress. The positive associations of adiposity with distress in multivariable analyses might be explained by residual confounding or reverse causality.

Hyperhomocysteinemia, methylenetetrahydrofolate reductase c.677C>T polymorphism and risk of cancer: cross-sectional and prospective studies and meta-analyses of 75,000 cases and 93,000 controls.

Global DNA hypomethylation associates with development of cancer. DNA hypomethylation also associates with hyperhomocysteinemia and MTHFR c.677C>T homozygosity, both of which may associate with increased risk of cancer. We tested the putative association of hyperhomocysteinemia with cancer and the association of the MTHFR c.677TC>T variant with hyperhomocysteinemia and with cancer. We performed a cross-sectional study of 5,949 Danish general population adults, a prospective study of 9,235 Danish general population adults with up to 60 years of registry surveillance, and meta-analyses of 231 studies including 74,671 cases and 93,344 controls. Cross-sectionally, plasma homocysteine levels were 12.9 and 11.6 µmol/L in those with and without cancer (p < 0.0001). However, homocysteine levels increased with age and age-adjusted odds ratio for any cancer in those with homocysteine levels >12.4 versus < 9.4 µmol/L did not differ from 1.0. In cancer-free participants, plasma homocysteine levels were 14.7 and 11.7 µmol/L in MTHFR c.677C>T homozygtes and noncarriers (p < 0.0001). Prospectively, hazard ratios for any cancer and for cancer subtypes in MTHFR c.677C>T homozygotes versus noncarriers did not differ from 1.0. However, in meta-analyses odds ratio for MTHFR c.677C>T homozygotes versus noncarriers were 1.07 (95% CI: 1.01-1.12) for any cancer, 1.77 (1.17-2.68) for esophagus cancer, 1.40 (1.19-1.66) for gastric cancer and 0.85 (0.77-0.94) for colorectal cancer. Increased plasma homocysteine levels are not associated with an increased age-adjusted risk of any cancer. However, MTHFR c.677C>T homozygosity with lifelong hyperhomocysteinemia and hence hypomethylation associate with increased risk of esophagus and gastric cancer, and with decreased risk of colorectal cancer.

C reactive protein and chronic obstructive pulmonary disease: a Mendelian randomisation approach.

BACKGROUND: It is unclear whether elevated plasma C reactive protein (CRP) is causally related to chronic obstructive pulmonary disease (COPD). The authors tested the hypothesis that genetically elevated plasma CRP causes COPD using a Mendelian randomisation design. METHODS: The authors measured high-sensitivity CRP in plasma, genotyped for four single nucleotide polymorphisms in the CRP gene, and screened for spirometry-defined COPD and hospitalisation due to COPD in 7974 individuals from the Copenhagen City Heart Study and in 32,652 individuals from the Copenhagen General Population Study. RESULTS: Elevated plasma CRP >3 mg/l compared with <1 mg/l was associated with risk estimates of 1.8 and 2.8 for spirometry-based COPD and of 1.6 and 1.8 for hospitalisation due to COPD in the Copenhagen City Heart Study and the Copenhagen General Population Study, respectively. Genotype combinations of the four CRP polymorphisms were associated with up to a 62% increase in plasma CRP. However, these genotype combinations did not associate with increased risk of COPD or hospitalisation due to COPD in either cohort or in the two cohorts combined. On instrumental variable analysis, a doubling of plasma CRP versus a doubling of genetically elevated CRP resulted in ORs for COPD of 1.27 (95% CI 1.25 to 1.30) versus 1.01 (0.81 to 1.26) and for COPD hospitalisation of 1.47 (1.43 to 1.51) versus 0.82(0.59 to 1.13). CONCLUSION: Although elevated CRP is related to both a diagnosis of COPD and subsequent hospital admission, genetically elevated plasma CRP is not associated with an increased risk of clinical COPD. This suggests that the association between CRP levels and COPD is not causal.

Does elevated C-reactive protein increase atrial fibrillation risk? A Mendelian randomization of 47,000 individuals from the general population.

OBJECTIVES: The purpose of this study was to test whether the association of C-reactive protein (CRP) with increased risk of atrial fibrillation is a robust and perhaps even causal association. BACKGROUND: Elevated levels of CRP previously have been associated with increased risk of atrial fibrillation. METHODS: We studied 10,276 individuals from the prospective Copenhagen City Heart Study, including 771 individuals who had atrial fibrillation during follow-up, and another 36,600 persons from the cross-sectional Copenhagen General Population Study, including 1,340 cases with atrial fibrillation. Individuals were genotyped for 4 CRP gene polymorphisms and had high-sensitivity CRP levels measured. RESULTS: A CRP level in the upper versus lower quintile associated with a 2.19-fold (95% confidence interval [CI]: 1.54- to 3.10-fold) increased risk of atrial fibrillation. Risk estimates attenuated slightly after multifactorial adjustment to 1.77 (95% CI: 1.22 to 2.55), and after additional adjustment for heart failure and plasma fibrinogen level to 1.47 (95% CI: 1.02 to 2.13) and 1.63 (95% CI: 1.21 to 2.20), respectively. Genotype combinations of the 4 CRP polymorphisms associated with up to a 63% increase in plasma CRP levels (p < 0.001), but not with increased risk of atrial fibrillation. The estimated causal odds ratio for atrial fibrillation by instrumental variable analysis for a doubling in genetically elevated CRP levels was lower than the odds ratio for atrial fibrillation observed for a doubling in plasma CRP on logistic regression (0.94 [95% CI: 0.70 to 1.27] vs. 1.36 [95% CI: 1.30 to 1.44]; p < 0.001). CONCLUSIONS: Elevated plasma CRP robustly associated with increased risk of atrial fibrillation; however, genetically elevated CRP levels did not. This suggests that elevated plasma CRP per se does not increase atrial fibrillation risk.

C-reactive protein and risk of venous thromboembolism in the general population.

OBJECTIVE: To examine the robustness of the association between C-reactive protein (CRP) levels and increased risk of venous thromboembolism (VTE) and to examine whether genetically elevated CRP levels cause VTE. METHODS AND RESULTS: In the prospective Copenhagen City Heart Study, we observed 10 388 participants for longer than 16 years, of whom 484 developed a VTE. In the cross-sectional Copenhagen General Population Study, we studied 36 616 participants, of whom 903 previously had a VTE. Levels of CRP greater than 3 mg/L versus less than 1 mg/L were associated with a 2.3- and 2.4-fold increased risk of VTE in the Copenhagen City Heart Study and the Copenhagen General Population Study, respectively. CRP levels in tertiles, quintiles, and octiles associated with a stepwise increase in VTE risk. CRP genotypes associated with an increase in plasma CRP levels up to 59% but did not associate consistently with risk of VTE in either study. The causal odds ratio for VTE for a doubling in genetically elevated CRP on instrumental variable analyses was lower than the odds ratio for VTE observed for a doubling in plasma CRP on logistic regression ([odds ratio and 95% CI] 0.80 [0.56 to 1.12] versus 1.17 [1.08 to 1.27]; P=0.04). CONCLUSIONS: We observed 47,000 participants from the general population, of whom 1387 developed VTE. Although elevated CRP levels robustly associated with increased risk of VTE, this may not necessarily be a causal association because genetically elevated CRP did not associate with VTE risk.

C-reactive protein and all-cause mortality--the Copenhagen City Heart Study.

AIMS: We tested whether elevated levels of C-reactive protein is robustly and causally associated with all-cause mortality. METHODS AND RESULTS: We studied 10 388 white persons from the general population. During 16 years 3124 persons died. We measured baseline high-sensitivity C-reactive protein and fibrinogen levels and genotyped for four C-reactive protein polymorphisms and two apolipoprotein E polymorphisms. Levels of C-reactive protein >3 mg/L vs. <1 mg/L associated with a multi-factorially adjusted two-fold increased risk of all-cause mortality. Stratifying C-reactive protein into tertiles, quintiles, or octiles resulted in step-by-step increased risk of all-cause mortality, even after fibrinogen adjustment. Finally, genetically elevated C-reactive protein levels associated with a causal hazard ratio of 0.94 (95% CI: 0.64-1.39) for all-cause mortality per doubling of C-reactive protein levels on instrumental variable analysis, for which the corresponding hazard ratio on Cox regression for a doubling in measured plasma C-reactive protein levels was 1.25 (1.21-1.29). As a positive control, a doubling in genetically elevated cholesterol levels via apolipoprotein E associated with a hazard ratio of 6.3 (1.8-22) for all-cause mortality. CONCLUSION: A single C-reactive protein measurement robustly associates with increased risk of all-cause mortality; however, this does not appear to be a causal association. Therefore, elevated C-reactive protein levels more likely are a marker of hidden, potentially fatal inflammatory disease.