Kim IY, et al. - Researchers intended to explore the interaction between caffeine intake with GRIN2A-rs4998386 and CYP1A2-rs762551 polymorphisms and how it effects the risk of Parkinson's disease (PD). They analyzed incident cases of PD and matched controls. Yielded data did not support the idea that the GRIN2A-rs4998386 or CYP1A2-rs762551 polymorphism and caffeine intake interaction determine PD risk.

Methods

• Researchers compared 829 incident cases of PD and 2,754 matched controls.
• Enrollees were selected from the following 3 large prospective ongoing cohorts: The Nurses' Health Study, the Health Professionals' Follow-up Study, and the Cancer Prevention Study II Nutrition Cohort.
• Cohort, birth year, source of DNA, date of DNA collection, and race were included as matching factors.
• Estimates of the relative risks and 95% confidence intervals were made via conditional logistic models.
• Both the multiplicative scale and the additive scale were used to test interactions.

Results

• A link was seen between caffeine intake with a lower PD risk (adjusted relative risk for highest vs lowest tertile = 0.70; 95% confidence interval, 0.57-0.86; p < .001).
• As per the analyses stratified by the GRIN2A-rs4998386 genotype, the multivariable-adjusted relative risk of PD comparing the highest to the lowest tertile of caffeine was found to be 0.69 (95% confidence interval, 0.55-0.88; p < .01) among individuals homozygous for the C allele, and 0.85 (95% confidence interval, 0.55-1.32; p=.47; p_RERI = .43) among carriers for the T allele.
• In either the multiplicative or additive scales, the interactions between caffeine and GRIN2A did not appear to be prominent.
• No notable interactions for CYP1A2-rs762551 and incident PD risk were discovered.