Serum vitamin C concentration was inversely associated with subsequent 20-year incidence of stroke in a Japanese rural community. The Shibata study.

BACKGROUND AND PURPOSE Epidemiological evidence suggests that vitamin C may decrease the risk of stroke. The purpose of the present study was to examine the association of serum vitamin C concentration with the subsequent incidence of stroke. METHODS In a Japanese rural community, a cohort of 880 men and 1241 women aged 40 years and older who were initially free of stroke was examined in 1977 and followed until 1997. The baseline examination included a measurement of serum vitamin C concentration. The incidence of stroke was determined by annual follow-up examinations and registry. RESULTS During the 20-year observation period, 196 incident cases of all stroke, including 109 cerebral infarctions and 54 hemorrhagic strokes, were documented. Strong inverse associations were observed between serum vitamin C concentration and all stroke (sex- and age-adjusted hazard ratios were 0.93, 0.72, and 0.59, respectively, for the second, third, and fourth quartiles compared with the first quartile; P for trend=0.002), cerebral infarction (0.71, 0.59, and 0.51; P for trend=0.015), and hemorrhagic stroke (0.89, 0.75, and 0. 45; P for trend=0.013). Additional adjustments for blood pressure, serum total cholesterol, body mass index, physical activity, smoking, alcohol drinking, antihypertensive medication, atrial fibrillation, and history of ischemic heart disease did not attenuate these associations markedly. CONCLUSIONS Serum vitamin C concentration was inversely related to the subsequent incidence of stroke. This relationship was significant for both cerebral infarction and hemorrhagic stroke. Additional mechanistic hypotheses may be required to explain our findings.