Consumption of green and roasted teas and the risk of stroke incidence: results from the Tokamachi-Nakasato cohort study in Japan

Background and purpose Green tea consumption is inversely associated with death from stroke. The purpose of the present study was to assess whether it is inversely associated with subsequent stroke incidence and whether this association is preserved even with roasted tea leaves. Methods In 1998, 6358 Japanese adults (2087 men and 4271 women) aged 4089 years without a history of stroke or heart disease completed a lifestyle questionnaire, including consumption of green tea or roasted tea. By the end of 2003, 110 stroke events (59 cerebral infarction events, 34 cerebral haemorrhage events, 15 subarachnoidal haemorrhage events and two stroke events of unspecified subtype) had been documented. Cox proportional hazards regression analysis was used to calculate the multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for total stroke events, cerebral infarction events and cerebral haemorrhage events according to consumption categories of green tea and roasted tea. Results A considerably lower risk was observed for total stroke incidence in both the middle (multivariable HR, 0.43; 95% CI, 0.25-0.74; P = 0.002) and the high (multivariable HR, 0.41; 95% CI, 0.24-0.70; P = 0.001) categories of green tea consumption. This inverse association was consistent even when cerebral infarction and cerebral haemorrhage were analysed separately. The consumption of roasted tea was not associated with stroke risk. Conclusions Green tea consumption is associated with a reduced risk of total stroke incidence, cerebral infarction and cerebral haemorrhage.