Assessment of the Relationship Between Inflammation and Glomerular Filtration Rate.

Background: Chronic kidney disease (CKD) is a global health problem. As it progresses to end stages, renal replacement therapy is required but ultimately, the best treatment is transplantation. Decreased renal function has been associated with an inflammatory state associated to primary CKD and in kidney transplant recipients (KTRs). Objective: To establish how the serum concentrations of some cytokines, such as interleukin (IL)-2, IL-8, IL-22, IL-17α, interferon-gamma, IL-4, and transforming growth factor-ß, correlate with various CKD stages. Methods: One hundred and forty-one KTRs between the ages of 18 and 75 years were included in the study. We also included 112 live kidney donors, 37 CKD PGCKD+3, and 76 GPhealthy. Participants were grouped according to their glomerular filtration rate (GFR) and their circulating cytokine levels, previously quantified by ELISA. Results: By linear regression analysis, we established the relation of each cytokine with the GFR. Transforming growth factor-ß correlated positively with the GFR in the study population, except in healthy individuals. A negative correlation of IL-8 and IL-17α and GFR was found in all cases. Conclusions: Whether these cytokines (IL-8 and IL-17α) could be used as inflammatory biomarkers indicating CKD progression, regardless of the type of population, remains to be prospectively determined.

Contexte: L'insuffisance rénale chronique (IRC) est un problème de santé mondial. Une thérapie de remplacement rénal est nécessaire au fur et à mesure que la maladie évolue vers les stades terminaux. Mais, en définitive, le meilleur traitement reste la transplantation. La réduction de la fonction rénale a été associée à un état inflammatoire associé à l'IRC primaire; une association observée aussi chez les receveurs d'une greffe de rein. Objectif: Déterminer la façon dont les concentrations sériques de certaines cytokines, notamment IL-2, IL-8, IL-22, IL-17a, IFN-γ, IL-4 et TGF-ß, corrèlent avec divers stades de l'IRC. Méthodologie: Ont été inclus dans l'étude 141 receveurs d'une greffe rénale âgés de 18 à 75 ans, 112 donneurs vivants de rein, 37 personnes atteintes d'IRC (PGIRC+3) et 76 personnes en bonne santé (PGen santé). Les sujets ont été regroupés en fonction de leur débit de filtration glomérulaire (DFGe) et de leur taux de cytokines en circulation, quantifiés préalablement par ELISA. Résultats: Une analyse de régression linéaire a servi à établir la relation entre chaque cytokine et le DFGe. Dans la population étudiée, une corrélation positive a été observée entre TGF-ß et le DFGe, sauf chez les individus sains. Dans tous les cas, la corrélation s'est avérée négative entre le DFGe et les taux d'IL-8 et d'IL-17a. Conclusion: Il reste à déterminer prospectivement si ces cytokines (IL-8 et IL-17a) pourraient être utilisées comme biomarqueurs inflammatoires pour indiquer la progression de l'IRC, quelle que soit la population.

Biotin supplementation causes erroneous elevations of results in some commercial serum 25-hydroxyvitamin d (25OHD) assays.

The Vitamin D External Quality Assessment Scheme (DEQAS) distributes serum samples globally, on a quarterly basis, to assess participants' performance of specific methods for 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25-(OH)2D). DEQAS occasionally circulates samples containing high levels of substances found in certain clinical situations e.g. 25-OHD2, 24,25-(OH)2D3, hypertriglyceridemia. The increased availability and use of health supplements containing biotin has led to case reports of assay interference in methods utilizing a biotin-streptavidin detection system. In October 2018, DEQAS included a serum sample (545) containing exogenous biotin (concentration =586 µg/L) which was analyzed by a total of 683 laboratories using 35 different methods. The same serum sample (544) without exogenous biotin was also included in the 5-sample set. All methods (760 laboratories) performed satisfactorily on sample 544 giving an All-Laboratory Trimmed Mean = 50.2 ± 6.5 nmol/L (±SD, CV = 12.9 %). The target value for this sample 544 (& 555) was 47.4 nmol/L as determined by Centers for Disease Control and Prevention (CDC) Atlanta, Georgia using their LC-MS/MS reference method. In contrast, #545 containing the exogenous biotin was reported by only 683 laboratories and gave an All-Laboratory Trimmed Mean = 66.8 ± 37.6 nmol/L (±SD, CV = 56.3 %). As expected, LC-MS/MS methods (143 labs) reported similar results for both 544 = 48.9 ± 4.4 nmol/L (±SD) and 545 = 48.3 ± 4.5 nmol/L (±SD) showing that assays involving chromatographic steps are unaffected by the presence of biotin. Several of the antibody-based assays including Abbott Architect, DiaSorin Liaison, Beckman Unicel and Siemens Centaur are also unaffected by the addition of biotin. Two assays, IDS-iSYS and Roche Total 25OHD, both of which use biotin-streptavidin, exhibit biotin interference yielding values with a significant positive bias for 545 of 102.6 nmol/L ± 78.7 nmol/L (±SD) and 517.8 nmol/L ± 209.8 nmol/L (±SD) respectively. Interestingly, the failure to report sample 545 data from 77 laboratories is due solely to those running Roche Total 25OHD or Roche Vitamin D Total II assays. Given the prevalence of the adversely affected assays (25 % of DEQAS users) and the high volume of 25OHD testing, clinicians using these assays should, where possible, only measure 25OHD when patients are off biotin.

Estimating uncertainty of target values for DEQAS serum materials.

The External Quality Assessment (EQA) scheme for vitamin D metabolites (DEQAS) distributes human serum samples to laboratories across the world to assess their performance in measuring serum total 25-hydroxyvitamin D [25(OH)D], i.e. the sum of the concentrations of serum 25(OH)D2 and 25(OH)D3. In 2013 DEQAS, in collaboration with the Vitamin D Standardization Program (VDSP), became an accuracy-based EQAS when the National Institute for Standards and Technology (NIST) began assigning 25(OH)D target values to DEQAS serum samples using their Joint Committee for Traceability in Laboratory Medicine (JCTLM) approved reference measurement procedure (RMP). Historically, NIST has performed 4 determinations of 25-OHD2 and 25-OHD3 on each sample and used the mean values to calculate a single 'target value' for Total 25-OHD against which performance was judged. By definition the target values cannot be exact and each is associated with a level of uncertainty. The total uncertainty (UNIST) has two components, one from the 25(OH)D2, and 25(OH)D3 measurements and the other associated with the calibration procedure. The total combined uncertainty is calculated by adding up these uncertainties. In future, uncertainties will be attached to the target value in each DEQAS serum sample, starting with the next distribution cycle in 2019. Confidence intervals obtained using these uncertainties will allow DEQAS participants to determine if their result agrees with the NIST assigned target value. Furthermore, if the value falls within the confidence interval the laboratory's assay would be regarded as traceable, i.e. standardized, to the NIST RMP.

External Quality Assessment of 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) assays.

The discovery that mutations of the CYP24A1 gene are a cause of idiopathic infantile hypercalcemia (IIH) has revived interest in measuring serum 24,25(OH)2D3. Several studies have also suggested that a high 25-hydroxyvitamin D3(25-OHD3):24,25(OH)2D3 ratio might provide additional diagnostic information in the investigation of vitamin D deficiency. Measurement of 24,25(OH)2D3 is necessarily restricted to laboratories with mass spectrometry methods although cross reactivity of the metabolite in immunoassays for 25-OHD is a potential cause of misleading results. The international External Quality Assessment (EQA) scheme for vitamin D metabolites (DEQAS) was set up in 1989. In 2013 DEQAS became an accuracy based EQA for 25-OHD with 'target values' assigned by the National Institute of Standards and Technology (NIST) Reference Measurement Procedure (RMP). A pilot scheme for serum 24,25(OH)2D3 was started in 2015 and participants were asked to measure the metabolite on each of the 5 samples sent out for 25-OHD. Inter-laboratory agreement was poor but this may reflect methodological differences, in particular different approaches to assay standardization. An important potential contribution to reducing variability among assays was the development by NIST of a 24,25(OH)2D3 RMP and its use in assigning values to SRMs 972a, 2973 and 2971, supported by the NIH Office of Dietary Supplements (ODS) as part of the Vitamin D Standardization Program (VDSP) effort.

Hydroxyvitamin D assays: An historical perspective from DEQAS.

Recent years have seen a substantial increase in demand for 25-hydroxyvitamin D (25-OHD) assays. DEQAS (the Vitamin D External Quality Assessment Scheme) has been monitoring the performance of these assays since 1989. The first DEQAS distribution was in June 1989 and results were submitted by 13 laboratories in the UK, two of which used HPLC/UV; the rest used ligand binding assays with a tritium tracer. Inter-laboratory CVs (ALTM) ranged from 29.3% (42.7nmol/L) to 53.7% (20.0nmol/L). Currently the scheme has participants in 56 countries using 30 methods or variants of methods. In January 2017, 918 participants returned results and inter-laboratory CVs (ALTM) ranged from 10.3% (73.1nmol/L) to 15.3% (29.4nmol/L). Over the last 27 years, there have been a number of significant milestones in assay development. The first major advance was the development of an iodinated 25-OHD tracer by Hollis and Napoli in 1992, subsequently used in an RIA kit marketed by DiaSorin. This and other commercial radioimmunoassays that followed brought 25-OHD assays within reach of many more non-specialist routine laboratories. With the introduction of fully automated non-isotopic assays without solvent extraction, measurement of 25-OHD became available to any clinical chemistry laboratory with an appropriate analytical platform. However, as the limitations of these non-extraction assays became apparent more laboratories started using LC-MS/MS methodology. Meanwhile the variable accuracy of 25-OHD methods has been addressed by the Vitamin D Standardization Program (VDSP) which encourages manufacturers to produce methods traceable to the reference measurement procedures (RMPs) of NIST, University of Ghent and the Centers for Disease Control and Prevention (CDC). DEQAS changed to an accuracy-based scheme in 2013 and now assesses assay accuracy against the NIST RMP. This review will use DEQAS results and statistics to chart the historical development in 25-OHD assay technology and highlight some of the problems encountered in obtaining reliable results for this most challenging of analytes.

Quality assessment of vitamin D metabolite assays used by clinical and research laboratories.

The Vitamin D External Quality Assessment Scheme (DEQAS) was launched in 1989 and monitors the performance of 25-hydroxyvitamin D (25-OHD) and 1,25- dihydroxyvitamin D (1,25(OH)2D) assays. In April 2015 a pilot scheme for 24,25-dihydroxyvitamin D (24,25(OH)2D) was introduced. The 25-OHD scheme is accuracy - based with target values assigned by the NIST Reference Measurement Procedure (RMP) for 25-OHD2 and 25-OHD3. A similar method is used to assign values for 3-epi-25-OHD. Five samples of human serum are distributed quarterly to over 1000 participants in 58 countries (April 2016) and clinical laboratories are expected to submit results within approximately 5 weeks. Research laboratories with assays run less frequently are not given a deadline. Archived samples with NIST- assigned values are also available. Performance is assessed on the first four samples with the fifth reserved for investigations e.g. recovery experiments or to assess the influence of other serum constituents such as lipids. DEQAS provides rapid feedback, with an on-line preliminary report available immediately after a participant submits results and a comprehensive report soon after the results deadline. In 2015, DEQAS investigations revealed that several 25-OHD immunoassays under-recovered 25-OHD2 and 25-OHD results were falsely low on a sample with a modestly raised triglyceride concentration. An RMP for 1,25 (OH)2D is not yet available and results are judged against the Method Mean. Free advice is available from the DEQAS Advisory Panel which includes experts on methodology and biostatistics. DEQAS collaborates closely with the Vitamin D Standardization Program (VDSP) and both organizations have successfully worked with participants and manufacturers to improve the accuracy of vitamin D assays.

Vitamin D measurement standardization: The way out of the chaos.

Substantial variability is associated with laboratory measurement of serum total 25-hydroxyvitamin D [25(OH)D]. The resulting chaos impedes development of consensus 25(OH)D values to define stages of vitamin D status. As resolving this situation requires standardized measurement of 25(OH)D, the Vitamin D Standardization Program (VDSP) developed methodology to standardize 25(OH)D measurement to the gold standard reference measurement procedures of NIST, Ghent University and CDC. Importantly, VDSP developed protocols for standardizing 25(OH)D values from prior research based on availability of stored serum samples. The effect of such retrospective standardization on prevalence of "low" vitamin D status in national studies reported here for The Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) and the German Health Interview and Examination Survey for Children and Adolescents (KIGGS, 2003-2006) was such that in NHANES III 25(OH)D values were lower than original values while higher in KIGGS. In NHANES III the percentage with values below 30, 50 and 75 nmol/L increased from 4% to 6%, 22% to 31% and 55% to 71%, respectively. Whereas in KIGGS after standardization the percentage below 30, 50, and 70 nmol/L decreased from 28% to 13%, 64% to 47% and 87% to 85% respectively. Moreover, in a hypothetical example, depending on whether the 25(OH)D assay was positively or negatively biased by 12%, the 25(OH)D concentration which maximally suppressed PTH could vary from 20 to 35ng/mL. These examples underscore the challenges (perhaps impossibility) of developing vitamin D guidelines using unstandardized 25(OH)D data. Retrospective 25(OH)D standardization can be applied to old studies where stored serum samples exist. As a way forward, we suggest an international effort to identify key prior studies with stored samples for re-analysis and standardization initially to define the 25(OH)D level associated with vitamin D deficiency (rickets/osteomalacia). Subsequent work could focus on defining inadequacy. Finally, examples reported here highlight the importance of suspending publication of meta-analyses based on unstandardized 25(OH)D results.

Developing vitamin D dietary guidelines and the lack of 25-hydroxyvitamin D assay standardization: The ever-present past.

Unstandardized laboratory measurement of 25-hydroxyvitamin D (25(OH)D) confounds efforts to develop clinical and public health vitamin D guidelines. The Vitamin D Standardization Program (VDSP), an international collaborative effort, was founded in 2010 to correct this problem. Nearly all published vitamin D research is based on unstandardized laboratory 25(OH)D measurements. While it is impossible to standardize all old data, it may be possible to identify a small subset of prior studies critical to guidelines development. Once identified it may be possible to calibrate their 25(OH)D values to the NIST and Ghent University reference measurement procedures using VDSP methods thereby permitting future guidelines to be based on standardized results. We simulated the calibration of a small set of ten clinical trials of vitamin D supplementation on achieved 25(OH)D under minimal sun exposure. These studies were selected because they played a prominent role in setting the 2010 vitamin D dietary reference intakes (DRI). Using random-effects meta-regression analysis, Vitamin D External Quality Assessment (DEQAS) data on assay bias was used to simulate the potential bias due to the lack of assay standardization by calibrating the achieved 25(OH)D levels from those 10 studies to: (1) the largest negative, and (2) the largest positive bias from the DEQAS all laboratory trimmed mean (ALTM) for the appropriate assay and year of analysis. For a usual vitamin D intake of 600IU/day the difference in mean achieved 25(OH)D values for those two options was 20nmol/L. However, without re-calibration of 25(OH)D values it is impossible to know the degree to which any of the current guidelines may have been biased. This approach may help stimulate the search for and standardization of that small subset of key studies and, in the cases where standardization is impossible, to identify areas of urgently needed vitamin D research.

Indwelling peritoneal catheters in patients with cirrhosis and refractory ascites.

BACKGROUND: The prevalence of spontaneous bacterial peritonitis (SBP) in hospitalised cirrhotics with ascites is 10-30%. Treatment for refractory ascites includes paracenteses, transjugular intrahepatic portosystemic shunt or drain placement; the latter is discouraged due to a perceived infection risk. AIM: This study aimed to evaluate the risk of bacterial peritonitis (BP) with peritoneal drains in patients with Child-Pugh class B or C cirrhosis and determine their impact on survival. METHODS: We conducted a retrospective review of end-stage liver disease (ESLD) patients with non-malignant, refractory ascites who had peritoneal drains placed for ≥3 days at Loyola University between 1999 and 2009. Cell counts were performed at drain placement and within 72 h. BP was defined as ascitic polymorphonuclear neutrophils >250/mm(3) . Univariate analysis assessed the association between demographics, laboratory markers and development of BP. Kaplan-Meier curve estimates by infection were constructed and survival distributions were compared using log-rank statistic. RESULTS: There were 227 drain placements during the study period. Twenty-two per cent were diagnosed with BP (12% had SBP at drain placement; 10% developed BP within 72 h). There was no association between BP and baseline characteristics. Patients who developed BP within 72 h of drain placement had 50% mortality at 5 months compared with 50 months in those without infection (log-rank P ≤ 0.003). CONCLUSION: In ESLD patients who received an indwelling peritoneal catheter, there was 10% risk of developing BP and significant mortality increase. Though placing drains is not the mainstay of treatment for refractory ascites, we confirm the theoretical adverse risk of peritoneal drains on infection and survival in cirrhotics.

Leveraging social influence to address overweight and obesity using agent-based models: the role of adolescent social networks.

The prevalence of adolescent overweight and obesity (hereafter, simply "overweight") in the US has increased over the past several decades. Individually-targeted prevention and treatment strategies targeting individuals have been disappointing, leading some to propose leveraging social networks to improve interventions. We hypothesized that social network dynamics (social marginalization; homophily on body mass index, BMI) and the strength of peer influence would increase or decrease the proportion of network member (agents) becoming overweight over a simulated year, and that peer influence would operate differently in social networks with greater overweight. We built an agent-based model (ABM) using results from R-SIENA. ABMs allow for the exploration of potential interventions using simulated agents. Initial model specifications were drawn from Wave 1 of the National Longitudinal Study of Adolescent Health (Add Health). We focused on a single saturation school with complete network and BMI data over two waves (n = 624). The model was validated against empirical observations at Wave 2. We focused on overall overweight prevalence after a simulated year. Five experiments were conducted: (1) changing attractiveness of high-BMI agents; (2) changing homophily on BMI; (3) changing the strength of peer influence; (4) shifting the overall BMI distribution; and (5) targeting dietary interventions to highly connected individuals. Increasing peer influence showed a dramatic decrease in the prevalence of overweight; making peer influence negative (i.e., doing the opposite of friends) increased overweight. However, the effect of peer influence varied based on the underlying distribution of BMI; when BMI was increased overall, stronger peer influence increased proportion of overweight. Other interventions, including targeted dieting, had little impact. Peer influence may be a viable target in overweight interventions, but the distribution of body size in the population needs to be taken into account. In low-obesity populations, strengthening peer influence may be a useful strategy.

Prediction of fat-free mass using bioelectrical impedance analysis in young adults from five populations of African origin.

BACKGROUND/OBJECTIVES: Bioelectrical impedance analysis (BIA) is used in population and clinical studies as a technique for estimating body composition. Because of significant under-representation in existing literature, we sought to develop and validate predictive equation(s) for BIA for studies in populations of African origin. SUBJECTS/METHODS: Among five cohorts of the Modeling the Epidemiologic Transition Study, height, weight, waist circumference and body composition, using isotope dilution, were measured in 362 adults, ages 25-45 with mean body mass indexes ranging from 24 to 32. BIA measures of resistance and reactance were measured using tetrapolar placement of electrodes and the same model of analyzer across sites (BIA 101Q, RJL Systems). Multiple linear regression analysis was used to develop equations for predicting fat-free mass (FFM), as measured by isotope dilution; covariates included sex, age, waist, reactance and height(2)/resistance, along with dummy variables for each site. Developed equations were then tested in a validation sample; FFM predicted by previously published equations were tested in the total sample. RESULTS: A site-combined equation and site-specific equations were developed. The mean differences between FFM (reference) and FFM predicted by the study-derived equations were between 0.4 and 0.6 kg (that is, 1% difference between the actual and predicted FFM), and the measured and predicted values were highly correlated. The site-combined equation performed slightly better than the site-specific equations and the previously published equations. CONCLUSIONS: Relatively small differences exist between BIA equations to estimate FFM, whether study-derived or published equations, although the site-combined equation performed slightly better than others. The study-derived equations provide an important tool for research in these understudied populations.

Patterns of sodium and potassium excretion and blood pressure in the African Diaspora.

Habitual levels of dietary sodium and potassium are correlated with age-related increases in blood pressure (BP) and likely have a role in this phenomenon. Although extensive published evidence exists from randomized trials, relatively few large-scale community surveys with multiple 24-h urine collections have been reported. We obtained three 24-h samples from 2704 individuals from Nigeria, Jamaica and the United States to evaluate patterns of intake and within-person relationships with BP. The average (±s.d.) age and weight of the participants across all the three sites were 39.9±8.6 years and 76.1±21.2 kg, respectively, and 55% of the total participants were females. Sodium excretion increased across the East-West gradient (for example, 123.9±54.6, 134.1±48.8, 176.6±71.0 (±s.d.) mmol, Nigeria, Jamaica and US, respectively), whereas potassium was essentially unchanged (for example, 46.3±22.9, 40.7±16.1, 44.7±16.4 (±s.d.) mmol, respectively). In multivariate analyses both sodium (positively) and potassium (negatively) were strongly correlated with BP (P<0.001); quantitatively the association was stronger, and more consistent in each site individually, for potassium. The within-population day-to-day variation was also greater for sodium than for potassium. Among each population group, a significant correlation was observed between sodium and urine volume, supporting the prior finding of sodium as a determinant of fluid intake in free-living individuals. These data confirm the consistency with the possible role of dietary electrolytes as hypertension risk factors, reinforcing the relevance of potassium in these populations.

Energy expenditure in young adult urban informal settlement dwellers in South Africa.

Obesity prevalences are increasing in industrialized and developing countries. As a pilot for a comparative study of physical activity and weight change, we assessed energy expenditure (EE) in young black South African adults living in an urban informal settlement. Total EE (TEE) was assessed using doubly labeled water, activity EE (AEE) and activity patterns by accelerometry and body composition by isotope dilution. Twenty young women and eight men were enrolled. Over 50% of the women and no men were obese (mean BMI 31.0 and 21.6 kg/m(2), respectively). Women had significantly lower TEE and AEE after adjustment for body size, as well as lower levels of moderate and vigorous activity. Neither TEE nor AEE was associated with BMI or percent body fat, whereas percent time in vigorous activity was modestly negatively associated with adiposity. These data add to the small literature on EE and activity among populations undergoing epidemiologic transitions.

Total daily energy expenditure in black and white, lean and obese South African women.

BACKGROUND/OBJECTIVES: In South Africa (SA), the prevalence of obesity in women is 56%, with black women being most at risk (62%). Studies in the United States have demonstrated ethnic differences in resting (REE) and total daily energy expenditure (TDEE) between African American (AA) and their white counterparts. We investigated whether differences in EE exist in black and white SA women, explaining, in part, the ethnic obesity prevalence differences. SUBJECTS/METHODS: We measured REE, TDEE and physical activity EE (PAEE) in lean (BMI <25 kg m(-2)) and obese (BMI >30 kg m(-2)) SA women (N=44, 30+/-6 year). REE, TDEE, PAEE and total awake EE were measured during a 21 h stay in a respiration chamber. RESULTS: Black and white subjects within obese and lean groups were not significantly different for age, mass, BMI and % body fat. However, fat-free mass (kg FFM) was consistently lower in the black women (P<0.01) in both weight groups. After adjusting EE measurements for differences in FFM, REE was not significantly different for either body weight or ethnicity, although 24 h TDEE (kJ) was significantly greater in the obese women (P<0.01) and white women (P<0.05). Total awake non-PAEE was not significantly different for either groups, while total awake time was only significantly lower for the lean groups (P<0.01). Total PAEE (kJ min(-1)) was significantly lower in the lean (P<0.001) and black groups (P<0.01). CONCLUSIONS: In this sample of matched, lean and obese, black and white SA women, differences in TDEE were largely explained by ethnic differences in PAEE, and were not as a result of ethnic differences in REE.

Issues related to modeling the body mass index-mortality association: the shape of the association and the effects of smoking status.

Research on the relationship between body mass index (BMI) and mortality has led to conflicting results; a lack of agreement about how to adjust for confounders, such as smoking status, has added to the problem. Complicating such analyses is the fact that the BMI-mortality association is not a symmetric quadratic relationship; the distribution tends to be skewed to the right, causing the optimal BMI--where mortality is at a minimum--to be overestimated. One way to overcome this problem is by transformation of the BMI distribution to normality. The authors suggest several approaches for doing so, including the use of 1/BMI, or lean body mass index, instead of BMI in modeling. Data sets on 50 cohorts from approximately 30 international studies were used to examine the association (direct, inverse, quadratic or none) between BMI and mortality and to investigate the possible interaction of smoking status. Of the 50 cohorts, 36 showed a quadratic association between BMI and mortality, 10 showed no association and 1 showed a direct association between lean BMI and mortality. Only three cohorts showed a significant interaction between BMI and smoking, which was approximately what one would expect from a 5% significance test, even if no interaction existed. The association between BMI and mortality is not changed when smoking status is ignored in a model or when data on smokers are excluded from analysis. The methodology used in this study could be extended to look for other interactions.

Hypertension in Mexico and among Mexican Americans: prevalence and treatment patterns.

Increased social and economic integration across the US-Mexican borders has led to important new developments in public health. Lower levels of cardiovascular mortality have been observed among Mexican Americans (MAs) although few direct comparisons have been undertaken with Mexico. Using survey data in the respective countries we examined blood pressure (BP) levels, hypertension prevalence and patterns of awareness, treatment and control in Mexico and among MAs. A national representative sample of the adult population from Mexico collected in 2000 (N=49 294), and data on 8688 MA participants in the 1999-2004 National Health and Nutrition Examination survey from the United States were available for analysis. US-born MAs and those born in Mexico were analysed separately in the US data. Lack of direct standardization of methods between surveys necessitated statistical adjustment of BP values. Analyses were based on persons aged 25-64 in each country. Sex- and age-adjusted mean systolic/diastolic BPs were 122/80, 119/71 and 120/73 in Mexicans, immigrant MAs and US-born MAs, respectively. The prevalences of hypertension (BP > or = 140/90 or treatment) were 33, 17 and 22%. Hypertension control rates were 3.7, 32.1 and 37.9%, in the same groups. Awareness and treatment rates were 25 and 13% in Mexico and 54 and 46% among MAs in the United States, respectively. Hypertension appears to be more common in Mexico than among Mexican immigrants to the United States. Despite relatively low access to health insurance in the United States, hypertension control increased over the course of this migration.

Activity, adiposity and weight change in Jamaican adults / Actividad, adiposidad y cambio de peso en los adultos jamaicanos

OBJECTIVE: Populations in developing countries are particularly vulnerable to the development of obesity in the period of rapid transition to a more modernized lifestyle. We sought to determine the relationship between activity energy expenditure (AEE), adiposity and weight change in an adult population undergoing rapid socio-economic transition. METHODS: Total daily energy expenditure (TDEE) was measured using the doubly labelled water method, resting energy expenditure (REE) using indirect calorimetry and AEE calculated as the difference between TDEE and REE, in adults from a working class community in Spanish Town, Jamaica. During six years of follow-up, weight was measured between one and four times. Mixed effects regression modelling was used to test for association between components of the energy budget and weight change. RESULTS: Men (n = 17) weighed more but women (n = 18), had significantly more body fat, 38.5% vs 24.5%, respectively (p < 0.01). Men had higher levels of EE, particularly AEE after adjustment for body weight, 66.3 versus 46.4 kJ/kg.d for men and women, respectively (p < 0.001). At baseline, adjusted AEE was inversely associated with body fat in men and women, r = -0.46 and r = -0.48, respectively (p < 0.05). Mean rate of weight change was + 1.1 and + 1.2 kg/year for men and women, respectively. No component of EE, ie TDEE, REE or AEE, significantly predicted weight change in this small sample. CONCLUSIONS: These results suggest an important role for AEE in maintaining low levels of adiposity. The lack of association between EE and weight change, however, suggests populations in transition are at risk of obesity from environmental factors (eg dietary) other than simply declining physical activity levels.

OBJETIVO: Las poblaciones en los países en vía de desarrollo son particularmente vulnerables al desarrollo de la obesidad en el período de rápida transición a un estilo de vida más moderno. Buscamos determinar la relación entre el gasto energético por actividad (GEA), la adiposidad y el cambio de peso en una población adulta en proceso de rápida transición socio-económica. MÉTODOS: El gasto energético total diario (GETD) fue medido usando el método del agua doblemente marcada, gasto energético en reposo (GER) usando calorimetría indirecta y el GEA calculado como la diferencia entre GETD y GER, en adultos de una comunidad de clase obrera en Spanish Town, Jamaica. Durante seis años de seguimiento, el peso fue medido entre una y cuatro veces. Un modelo de regresión de efectos mixtos fue usado para probar la asociaciF3n entre los componentes del presupuesto de la energEDa y el cambio de peso. RESULTADOS: Los hombres (n = 17) pesaron más pero las mujeres (n = 18) teníEDan significativamente más grasa corporal, 38.5% frente a 24.5%, respectivamente (p < 0.01). Los hombres tenían niveles más altos de GE, particularmente GEA después del ajuste por peso corporal, 66.3 frente a 46.4 kJ/kg.d para los hombres y mujeres, respectivamente (p < 0.001). Al inicio, el GEA ajustado estaba inversamente asociado con la grasa del cuerpo en los hombres y mujeres, r = -0.46 y r = -0.48, respectivamente (p < 0.05). La tasa media de cambio de peso fue +1.1 y +1.2 kg/ano para los hombres y mujeres, respectivamente. Ningún componente de GE, es decir, GETD, GER o GEA, predijo significativamente el cambio de peso en esta muestra pequeña. CONCLUSIONES: Estos resultados sugieren un papel importante del GEA en cuanto a mantener niveles bajos de adiposidad. Sin embargo, la falta de asociación entre GE y cambio de peso, sugiere que las poblaciones en transición corren el riesgo de obesidad debido a factores ambientales (p.ej. dietéticos) distintos de la mera...

Activity, adiposity and weight change in Jamaican adults.

OBJECTIVE: Populations in developing countries are particularly vulnerable to the development of obesity in the period of rapid transition to a more modernized lifestyle. We sought to determine the relationship between activity energy expenditure (AEE), adiposity and weight change in an adult population undergoing rapid socio-economic transition. METHODS: Total daily energy expenditure (TDEE) was measured using the doubly labelled water method, resting energy expenditure (REE) using indirect calorimetry and AEE calculated as the difference between TDEE and REE, in adults from a working class community in Spanish Town, Jamaica. During six years of follow-up, weight was measured between one and four times. Mixed effects regression modelling was used to test for association between components of the energy budget and weight change. RESULTS: Men (n = 17) weighed more but women (n = 18), had significantly more body fat, 38.5% vs 24.5%, respectively (p < 0.01). Men had higher levels of EE, particularly AEE after adjustment for body weight, 66.3 versus 46.4 kJ/kg.d for men and women, respectively (p < 0.001). At baseline, adjusted AEE was inversely associated with body fat in men and women, r = -0.46 and r = -0.48, respectively (p < 0.05). Mean rate of weight change was + 1.1 and + 1.2 kg/year for men and women, respectively. No component of EE, ie TDEE, REE or AEE, significantly predicted weight change in this small sample. CONCLUSIONS: These results suggest an important role for AEE in maintaining low levels of adiposity. The lack of association between EE and weight change, however, suggests populations in transition are at risk of obesity from environmental factors (eg dietary) other than simply declining physical activity levels.

Preoperative differences between male and female patients with sleep apnea.

OBJECTIVES/HYPOTHESIS: To evaluate the differences between female and male patients with obstructive sleep apnea syndrome (OSAS) in the preoperative period. STUDY DESIGN: Nonrandomized cross-sectional study. METHODS: An analysis of 686 patients (111 women and 575 men) with OSAS was completed. Multivariate modeling techniques were employed to correlate gender with the preoperative respiratory disturbance index (RDI), apnea index (AI), hypopnea index (HI), body mass index (BMI), age, and initial symptoms. RESULTS: At presentation, the male patients were significantly younger and had a lower BMI and a higher RDI and AI than the female patients. For the entire OSAS population studied, the RDI increased as the BMI increased (correlation coefficient [r] = 0.35, P = <.001). For the female patients there was a weaker correlation (r = 0.21, P =.034), and in male patients there was a stronger correlation (r = 0.40, P <.001). For the entire population there was a negative correlation between age and RDI (r = -0.15, P <.001). In female patients there was a nonsignificant correlation (r = -0.09, P =.35), and in male patients the correlation was significant (r = -0.16, P <.001). There was no difference in the reporting of the number of symptoms based on gender (P =.355). Female patients noted headaches on awakening more commonly than male patients (P =.001), and male patients noted snoring (P =.014) and stopping breathing during sleep (P =.001) more often than female patients. CONCLUSIONS: The analysis demonstrated that within a surgical population sample, gender differences exist. The findings of this series were as follows: 1) Apnea severity in women was less weight-dependent than in men; (2) in men there was a significant negative correlation between age and apnea severity; and (3) female and male patients reported the same number of signs or symptoms on presentation, although certain signs and symptoms were more commonly reported based on gender. Current clinical evaluation practices must take into account this gender disparity.