Platelet count and total and cause-specific mortality in the Women's Health Initiative

Purpose We used data from the Women's Health Initiative to examine the association of platelet count with total mortality, coronary heart disease (CHD) mortality, cancer mortality, and non-CHD/noncancer mortality. Methods Platelet count was measured at baseline in 159,746 postmenopausal women and again in year 3 in 75,339 participants. Participants were followed for a median of 15.9 years. Cox proportional hazards models were used to estimate the relative mortality hazards associated with deciles of baseline platelet count and of the mean of baseline + year 3 platelet count. Results Low and high deciles of both baseline and mean platelet count were positively associated with total mortality, CHD mortality, cancer mortality, and non-CHD/noncancer mortality. The association was robust and was not affected by adjustment for a number of potential confounding factors, exclusion of women with comorbidity, or allowance for reverse causality. Low- and high-platelet counts were associated with all four outcomes in never smokers, former smokers, and current smokers. Conclusions In this large study of postmenopausal women, both low- and high-platelet counts were associated with total and cause-specific mortality.