Circulating vitamin C and the risk of cardiovascular diseases: A Mendelian randomization study.

BACKGROUND AND AIMS: The impact of vitamin C supplementation on the risk of cardiovascular diseases (CVDs) remains uncertain with inconsistent evidence obtained from observational studies and randomized clinical trials (RCTs). We aimed to assess possible causal associations of vitamin C with major CVD events as well as their risk factors using Mendelian randomization (MR) design. METHODS AND RESULTS: Nine genetic variants associated with vitamin C at genome-wide significance (p < 5 × 10-8) were used as instrumental variables to predict plasma vitamin C levels. The primary outcomes were coronary artery disease (Ncase = 122,733 and Ncontrol = 424,528), atrial fibrillation (Ncase = 60,620 and Ncontrol = 970,216), heart failure (Ncase = 47,309 and Ncontrol = 930,014), and ischemic stroke (Ncase = 40,585 and Ncontrol = 406,111). Several CVD risk factors were also evaluated in secondary analyses. Two-sample MR analyses were performed using the inverse variance weighted method, with several sensitivity analyses. Genetically determined higher levels of plasma vitamin C were not significantly associated with any of the four examined CVD events. Likewise, there is no convincing evidence for the associations between genetically determined vitamin C and CVD risk factors, including higher blood lipids, higher blood pressure, and abnormal body composition. Sensitivity analyses using different analytical approaches yielded consistent results. Additionally, MR assumptions did not seem to be violated. CONCLUSION: This MR study does not support a causal protective role to circulate vitamin C levels on various types of CVD events. In combination with previous RCT results, our findings suggest that vitamin C supplementation to increase circulating vitamin C levels may not help in CVD prevention.

Hypertension and High Blood Pressure Are Associated With Dementia Among Chinese Dwelling Elderly: The Shanghai Aging Study.

Background: To explore the association between blood pressure and cognition in older participants in the Shanghai Aging Study. Methods: Data were drawn from 3,327 participants at the baseline of Shanghai Aging Study. History of hypertension was inquired and confirmed from participants' medical records. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured by research nurses in the early morning. Participants were diagnosed with "cognitive normal," "mild cognitive impairment (MCI)," or "dementia" by neurologists using DSM-IV and Petersen criteria. Multivariate logistic regression was used to evaluate the association between history of hypertension, duration of hypertension, SBP, DBP, or classification of blood pressure and cognitive function. Generalized linear model was used to assess the relation between duration of hypertension, SBP, or DBP and Mini Mental State Examination (MMSE). Results: A significantly higher proportion of hypertension [78 (76.5%)] was found in participants with dementia than in those with MCI [347 (59.3%)] and cognitive normal [1,350 (51.1%)] (P < 0.0001). Participants with dementia had significantly higher SBP [157.6 (26.1) mmHg] than those with MCI [149.0 (23.7) mmHg] and cognitive normal [143.7 (22.6) mmHg] (P < 0.0001). After adjusting for sex, age, education, living alone, body mass index, anxiety, depression, heart disease, diabetes, and stroke, the likelihood of having dementia was positively associated with history of hypertension (OR = 2.10; 95% CI: 1.22, 3.61), duration of hypertension (OR = 1.02 per increment year; 95% CI: 1.01, 1.04), higher SBP (OR = 1.14 per increment of 10 mmHg; 95% CI: 1.04, 1.25), higher DBP (OR = 1.22 per increment of 10 mmHg; 95% CI: 1.02, 1.45), moderate hypertension (OR = 2.09; 95% CI: 1.10, 3.99), or severe hypertension (OR = 2.45; 95% CI: 1.20, 4.99). The MMSE score was inversely correlated to duration of hypertension (ß = -0.0088 per increment year; 95% CI: -0.0158, -0.0018, P = 0.0132), SBP (ß = -0.0655 per increment of 10 mmHg; 95% CI: -0.1022, -0.0288, P = 0.0005), and DBP (ß = -0.1230 per increment of 10 mmHg; 95% CI: -0.1915, -0.0545, P = 0.0004). Conclusion: Our results suggest that hypertension and high blood pressure may be potential risk factors for dementia. Blood pressure management for the elderly may be important for maintaining cognitive vitality.

Fine Particulate Air Pollution and Daily Mortality. A Nationwide Analysis in 272 Chinese Cities.

RATIONALE: Evidence concerning the acute health effects of air pollution caused by fine particulate matter (PM2.5) in developing countries is quite limited. OBJECTIVES: To evaluate short-term associations between PM2.5 and daily cause-specific mortality in China. METHODS: A nationwide time-series analysis was performed in 272 representative Chinese cities from 2013 to 2015. Two-stage Bayesian hierarchical models were applied to estimate regional- and national-average associations between PM2.5 concentrations and daily cause-specific mortality. City-specific effects of PM2.5 were estimated using the overdispersed generalized additive models after adjusting for time trends, day of the week, and weather conditions. Exposure-response relationship curves and potential effect modifiers were also evaluated. MEASUREMENTS AND MAIN RESULTS: The average of annual mean PM2.5 concentration in each city was 56 µg/m3 (minimum, 18 µg/m3; maximum, 127 µg/m3). Each 10-µg/m3 increase in 2-day moving average of PM2.5 concentrations was significantly associated with increments in mortality of 0.22% from total nonaccidental causes, 0.27% from cardiovascular diseases, 0.39% from hypertension, 0.30% from coronary heart diseases, 0.23% from stroke, 0.29% from respiratory diseases, and 0.38% from chronic obstructive pulmonary disease. There was a leveling off in the exposure-response curves at high concentrations in most, but not all, regions. The associations were stronger in cities with lower PM2.5 levels or higher temperatures, and in subpopulations with elder age or less education. CONCLUSIONS: This nationwide investigation provided robust evidence of the associations between short-term exposure to PM2.5 and increased mortality from various cardiopulmonary diseases in China. The magnitude of associations was lower than those reported in Europe and North America.