TABLE 3.
Coffee, tea, and caffeine intake in relation to Parkinson's disease risk, The Singapore Chinese Health Study, 1993-2005
| Characteristic | No. of person-years | No. of cases | RR*,† | 95% CI* | RR‡ | 95% CI | RR§ | 95% CI |
|---|---|---|---|---|---|---|---|---|
| Coffee | ||||||||
| None/less than daily | 173,379 | 55 | 1.00 | 1.00 | 1.00 | |||
| 1 cup/day | 214,325 | 60 | 0.91 | 0.63, 1.391 | 0.96 | 0.67, 1.39 | 1.05 | 0.70, 1.57 |
| ≥2 cups/day | 206,382 | 42 | 0.68 | 0.45, 1.01 | 0.78 | 0.52, 1.17 | 1.04 | 0.53, 2.03 |
| p for trend | 0.059 | 0.24 | 0.88 | |||||
| Black tea | ||||||||
| Nondrinker | 381,656 | 120 | 1.00 | 1.00 | 1.00 | |||
| 1st tertile (<5 cups/month) | 77,603 | 20 | 0.89 | 0.55, 1.42 | 0.87 | 0.54, 1.40 | 0.87 | 0.54, 1.40 |
| 2nd tertile (5-<23 cups/month) | 67,645 | 11 | 0.55 | 0.30, 1.03 | 0.53 | 0.29, 1.00 | 0.54 | 0.29, 1.00 |
| 3rd tertile (≥23 cups/month) | 67,181 | 6 | 0.29 | 0.13, 0.65 | 0.28 | 0.12, 0.64 | 0.29 | 0.13, 0.67 |
| p for trend | 0.0006 | 0.0004 | 0.0006 | |||||
| Green tea | ||||||||
| Nondrinker | 353,385 | 93 | 1.00 | 1.00 | 1.00 | |||
| 1st tertile (<5 cups/month) | 105,575 | 30 | 1.11 | 0.74, 1.68 | 1.10 | 0.73, 1.67 | 1.10 | 0.73, 1.67 |
| 2nd tertile (5-<23 cups/month) | 62,422 | 16 | 1.00 | 0.59, 1.70 | 0.98 | 0.58, 1.68 | 1.00 | 0.58, 1.70 |
| 3rd tertile (≥23 cups/month) | 72,705 | 18 | 0.84 | 0.50, 1.40 | 0.84 | 0.50, 1.40 | 0.93 | 0.55, 1.57 |
| p for trend | 0.61 | 0.59 | 0.86 | |||||
| Daily caffeine intake | ||||||||
| 1st quartile (<45.8 mg) | 146,025 | 51 | 1.00 | 1.00 | ||||
| 2nd quartile (45.8-<83.7 mg) | 148,495 | 48 | 0.96 | 0.65, 1.42 | 1.00 | 0.68, 1.49 | ||
| 3rd quartile (83.7-<141.1 mg) | 152,325 | 30 | 0.57 | 0.36, 0.89 | 0.62 | 0.39, 0.97 | ||
| 4th quartile (≥141.1 mg) | 147,241 | 28 | 0.55 | 0.35, 0.88 | 0.64 | 0.40, 1.03 | ||
| p for trend | 0.002 | 0.016 |
*
RR, relative risk; CI, confidence interval
†
Adjusted for age at recruitment (years), year of interview (1993-1995, 1996-1998), gender, dialect (Hokkien, Cantonese), and level of education (no formal education, primary school, secondary school or higher)
‡
Further adjusted for baseline smoking status (never, former, or current smoker) in addition to the factors listed in the second footnote.
§
Further adjusted for total caffeine intake (mg/day) in addition to smoking status (never, former, or current smoker) and the factors listed in the second footnote.