Introduction Accumulating evidence suggests that Vitamin D deficiency may be a risk factor for cardiovascular disease but its association with the risk of stroke is uncertain.
Methods 25-hydroxyvitamin D (25 (OH)D) was measured in 6803 ambulatory primary-care patients aged ≥65 years (mean age 73 years; 58% women) who participated in the German Epidemiological Trial on Ankle-Brachial Index (getABI). Participants had their baseline assessment in October 2001 and were followed for stroke for up to 7 years.
Results During a mean follow-up of 5.7 years, 249 participants had a stroke (84% ischaemic), a stroke rate of 6.5 per 1000 person-years. The risk of stroke increased with decreasing baseline 25 (OH)D levels (p for trend across quartiles <0.001). Compared to participants in the highest 25 (OH)D quartile (>53.7 nmol/l), participants in the lowest quartile (<24.5 nmol/l) had twice the risk of any stroke (HR 1.99, 95% CI 1.35 to 2.92) and a 70% higher risk of ischaemic stroke (1.72, 1.13 to 2.61) in Cox proportional hazards models adjusting for age, sex, education, smoking status, body mass index, renal function, and prior stroke. Additional adjustment for conventional cardiovascular risk factors and cardiovascular disease at baseline slightly attenuated these associations (any stroke: 1.76, 1.19 to 2.60; ischaemic stroke: 1.49, 0.97 to 2.27). Results were similar when 310 participants with prior stroke were excluded.
Conclusion Low vitamin D levels were associated with an increased risk of stroke in this prospective cohort study. This association was independent of several important confounders and only partly explained by conventional risk factors and cardiovascular disease as potential causal intermediates.
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