GRIN2A and Parkinson disease: Denmark (1,288 cases and 1,394 controls) had by far the largest dataset and the strongest PD–coffee association (P<0.001), and it confirmed GRIN2A–coffee interaction with statistical significance (one-sided PInteraction = 0.04) in the same direction as GWAIS: inverse association of coffee with PD was significantly stronger in GRIN2A rs4998386_T allele carriers (OR = 0.42/3.88 = 0.11) than in CC homozygotes (OR = 0.50).