Plasma and blood viscosity in the prediction of cardiovascular disease and mortality in the Scottish Heart Health Extended Cohort Study.

Background There is increasing evidence that blood viscosity and its major determinants (haematocrit and plasma viscosity) are associated with increased risks of cardiovascular disease (CVD) and premature mortality; however, their predictive value for CVD and mortality is not clear. Methods We prospectively assessed the added predictive value of plasma viscosity and whole blood viscosity and haematocrit in 3386 men and women aged 30-74 years participating in the Scottish Heart Health Extended Cohort study. Results Over a median follow-up of 17 years, 819 CVD events and 778 deaths were recorded. Hazard ratios (95% confidence intervals) for a 1 SD increase in plasma viscosity, adjusted for major CVD risk factors, were 1.12 (1.04-1.20) for CVD and 1.20 (1.12-1.29) for mortality. These remained significant after further adjustment for plasma fibrinogen: 1.09 (1.01-1.18) and 1.13 (1.04-1.22). The corresponding results for blood viscosity were 0.99 (0.90, 1.09) for CVD, and 1.11 (1.01, 1.22) for total mortality after adjustment for major CVD risk factors; and 0.97 (0.88, 1.08) and 1.06 (0.96, 1.18) after further adjustment for fibrinogen. Haematocrit showed similar associations to blood viscosity. When added to classical CVD risk factors, plasma viscosity improved the discrimination of CVD and mortality by 2.4% (0.7-4.4%) and 4.1% (2.0-6.5%). Conclusions Although plasma and blood viscosity may have a role in the pathogenesis of CVD and mortality, much of their association with CVD and mortality is due to the mutual effects of major CVD risk factors. However, plasma viscosity adds to the discrimination of CVD and mortality and might be considered for inclusion in multivariable risk scores.

Relationship between outdoor temperature and cardiovascular disease risk factors in older people.

Background Previous studies demonstrated that lower outdoor temperatures increase the levels of established cardiovascular disease risk factors, such as blood pressure and lipids. Whether or not low temperatures increase novel cardiovascular disease risk factors levels is not well studied. The aim was to investigate associations of outdoor temperature with a comprehensive range of established and novel cardiovascular disease risk factors in two large Northern European studies of older adults, in whom cardiovascular disease risk is increased. Design and methods Data came from the British Regional Heart Study (4252 men aged 60-79 years) and the Prospective Study of Pravastatin in the Elderly at Risk (5804 men and women aged 70-82 years). Associations between outdoor temperature and cardiovascular disease risk factors were quantified in each study and then pooled using a random effects model. Results With a 5℃ lower mean temperature, total cholesterol was 0.04 mmol/l (95% confidence interval (CI) 0.02-0.07) higher, low density lipoprotein cholesterol was 0.02 mmol/l (95% CI 0.01-0.05) higher and SBP was 1.12 mm Hg (95% CI 0.60-1.64) higher. Among novel cardiovascular disease risk factors, C-reactive protein was 3.3% (95% CI 1.0-5.6%) higher, interleukin-6 was 2.7% (95% CI 1.1-4.3%) higher, and vitamin D was 11.2% (95% CI 1.0-20.4%) lower. Conclusions Lower outdoor temperature was associated with adverse effects on cholesterol, blood pressure, circulating inflammatory markers, and vitamin D in two older populations. Public health approaches to protect the elderly against low temperatures could help in reducing the levels of several cardiovascular disease risk factors.

Associations of time of day with cardiovascular disease risk factors measured in older men: results from the British Regional Heart Study.

OBJECTIVE: We estimated associations of time of day with cardiovascular disease (CVD) risk factors measured in older men. METHODS: CVD risk factors (markers of inflammation and haemostasis, and cardiac markers) were measured on one occasion between 08:00 and 19:00 hours in 4252 men aged 60-79 years from the British Regional Heart Study. Linear models were used to estimate associations between time of day and risk factors. When an association was found, we examined whether the relationship between risk factors and cardiovascular mortality was affected by the adjustment for time of day using survival analyses. RESULTS: N-terminal pro-brain natriuretic peptide (NT-proBNP) levels increased by 3.3% per hour (95% CI 1.9% to 4.8%), interleukin-6 (IL-6) increased by 2.6% per hour (95% CI 1.8% to 3.4%), while tissue plasminogen activator (t-PA) decreased by 3.3% per hour (95% CI 3.7% to 2.9%); these associations were unaffected by adjustment for possible confounding factors. The percentages of variation in these risk factors attributable to time of day were less than 2%. In survival analyses, the association of IL-6, NT-proBNP and t-PA with cardiovascular mortality was not affected by the adjustment for time of day. C reactive protein, fibrinogen, D-dimer, von Willebrand factor and cardiac troponin T showed no associations with time of day. CONCLUSIONS: In older men, markers of inflammation (IL-6), haemostasis (t-PA) and a cardiac marker (NT-proBNP) varied by time of day. The contribution of time of day to variations in these markers was small and did not appear to be relevant for the CVD risk prediction.