Caffeine intake, smoking, and risk of Parkinson disease in men and women

Abstract

The authors prospectively examined whether caffeine intake was associated with lower risk of Parkinson disease (PD) in both men and women among 304,980 participants in the National Institutes of Health-AARP Diet and Health Study and whether smoking affected this relation. Multivariate odds ratios and 95% confidence intervals were derived from logistic regression models. Higher caffeine intake as assessed in 1995-1996 was monotonically associated with lower PD risk (diagnosed in 2000-2006) in both men and women. After adjustment for age, race, and physical activity, the odds ratio comparing the highest quintile of caffeine intake with the lowest was 0.75 (95% confidence interval: 0.60, 0.94; P(trend) = 0.005) for men and 0.60 (95% confidence interval: 0.39, 0.91; P(trend) = 0.005) for women. Further adjustment for duration of smoking and analyses carried out among never smokers showed similar results. A joint analysis with smoking suggested that smoking and caffeine may act independently in relation to PD risk. Finally, the authors conducted a meta-analysis of prospective studies and confirmed that caffeine intake was inversely associated with PD risk in both men and women. These findings suggest no gender difference in the relation between caffeine and PD.

Figure 1.

Odds ratios for Parkinson disease according to joint categories of baseline caffeine intake and smoking status, National Institutes of Health-AARP Diet and Health Study, 1995–2006. Caffeine intake was defined as low (first quintile), moderate (second and third quintiles), or high (fourth and fifth quintiles). Smoking status was defined as never smoker (striped bars), past smoker who had smoked for 1–29 years (gray bars), or past smoker who had smoked for ≥30 years/current smoker (dotted bars). Specific odds ratios appear above the bars.

Figure 2.

Results from a meta-analysis of prospective studies on coffee/caffeine intake and risk of Parkinson disease by gender. Odds ratios (ORs) and 95% confidence intervals (CIs) are for the highest coffee/caffeine intake categories versus the lowest. Squares indicate study-specific ORs; error bars indicate 95% CIs; and diamonds indicate results of pooled analyses. “Subtotal” represents the pooled OR within each subcategory, based on the random-effects model. “Overall” shows the pooled OR for all studies, based on the random-effects model. (HRT, hormone replacement therapy).