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.