Differential Effects of Black versus Green Tea on Risk of Parkinson's Disease in the Singapore Chinese Health Study by Louis C. Tan, Woon-Puay Koh, Jian-Min Yuan, Renwei Wang, Wing-Lok Au, June H. Tan, Eng-King Tan, and Mimi C. Yu
Data from Asian populations on dietary and lifestyle factors
associated with Parkinson's disease are sparse. In 1993-2005, the
authors examined these factors in relation to Parkinson's disease
in the Singapore Chinese Health Study, a prospective cohort of
63,257 Chinese men and women. Baseline data were collected through
in-person interviews using structured questionnaires. All 157
incident Parkinson's disease cases were identified either through
follow-up interviews or via linkage with hospital discharge
databases and Parkinson's disease outpatient registries and were
confirmed by review of medical records. Current versus never
smokers exhibited a reduced risk of Parkinson's disease (relative
risk = 0.29, 95% confidence interval: 0.16, 0.52). Total caffeine
intake was inversely related to Parkinson's disease risk
(p for trend = 0.002); the relative risk for the highest
versus lowest quartile was 0.55 (95% confidence interval: 0.35,
0.88). Black tea, a caffeine-containing beverage, showed an inverse
association with Parkinson's disease risk that was not confounded
by total caffeine intake or tobacco smoking (p for trend =
0.0006; adjusted relative risk for the highest vs. lowest tertile
of intake = 0.29, 95% confidence interval: 0.13, 0.67). Green tea
drinking was unrelated to Parkinson's disease risk. Diet had no
strong influence on risk. Ingredients of black tea other than
caffeine appear to be responsible for the beverage's inverse
association with Parkinson's disease.
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