Intake of Japanese and Chinese teas reduces risk of Parkinson’s disease☆
Introduction
The causes of Parkinson’s disease (PD) are unknown. But both genetic and environmental factors with complex interactions are thought to be responsible for the development and progression of the disease [1], [2]. The results of studies of twins suggested that genetic factors are important in early-onset PD cases while environmental factors play a predominant etiologic role in late-onset PD patients [3], [4]. There has been increasing evidence of a reduced risk of PD among coffee drinkers [5], [6], [7], [8], [9], [10], [11]. A meta-analysis by Hernán et al. showed that the risk of PD is about 30% lower among coffee drinkers than among non-coffee drinkers [12]. The most recent meta-analysis based on 26 studies also showed an inverse association between caffeine intake and the risk of PD (pooled relative risk = 0.75) [13]. Investigations on the association between intake of coffee or caffeine and PD were conducted mainly in the USA and in Europe [5], [6], [7], [8], [9], [11], [14], [15], [16], [17]. Relatively little is known about such relationships in Asian populations [10], [18], [19]. It is necessary to accumulate further evidence of the influence of the intake of coffee and caffeine on PD among Asian populations. In addition, investigations of the association between caffeine-containing beverage other than coffee, such as black tea and green tea, and the risk of PD are sparse, and what information is available has been conflicting [5], [9], [10], [14], [15], [18], [19]. In the Singapore Chinese Health study, a prospective cohort study, consumption of black tea and daily caffeine intake were inversely associated with the risk of PD whereas no association between consumption of coffee and green tea and PD risk was observed [18]. A case-control study in France showed that tea consumption was a risk factor for PD [14]. In the present case-control study of PD among Japanese, we investigated the association between the consumption of coffee, other caffeine-containing beverages, and caffeine and the risk of PD.
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Study subjects
Patients with PD were recruited at 3 university hospitals and 1 national hospital in Fukuoka Prefecture, a metropolitan area of Kyushu Island in southern Japan, and in 3 university hospitals, 3 national hospitals and 1 municipal hospital in Osaka, Kyoto, and Wakayama Prefectures, which are part of the Kinki region, which is located in the midwestern part of the mainland. Eligible cases were patients who were within 6 years of the onset of PD and who had been diagnosed by the collaborating
Results
The mean age of the 249 PD cases at onset was 65.3 years (standard deviation, 8.7 years), and the mean duration of PD was 3.2 years (standard deviation, 1.5 years). About 66% of cases (n = 164) were in modified Hoehn and Yahr (H&Y) stages 1–2.5. The characteristics of cases and control subjects are shown in Table 1. Cases and control subjects had a similar sex distribution. Cases were more likely to be older, report never having smoked, have a lower body mass index, and have a higher intake of
Discussion
The present case–control study in Japan showed that intake of coffee, black tea, Japanese and Chinese teas, and caffeine was significantly inversely associated with the risk of PD. Our results are in agreement with the majority of the previous epidemiological studies that found an association between the intake of coffee and caffeine and a reduced risk of PD [5], [6], [7], [8], [9], [10], [11]. A meta-analysis based on 7 cohort studies, 2 nested case-control studies, 16 case-control studies,
Acknowledgments
None of the authors had any personal or financial conflict of interest. This study was supported by Health and Labour Sciences Research Grants, Research on Intractable Diseases, Research Committee on Epidemiology of Intractable Diseases from the Ministry of Health, Labour, and Welfare, Japan.
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The review of this paper was entirely handled by an Associate Editor, Eng-King Tan.