UCHL1 S18Y variant is a risk factor for Parkinson’s disease in Japan

BMC Neurology

Table 5 Interaction between UCHL1 S18Y polymorphism and caffeine intake affecting sporadic Parkinson’s disease in a Japanese population

	Caffeine intake
	≥ 161.7 mg/4184 kJ		< 161.7 mg/4184 kJ
Genotype	No. cases/controls	Adjusted OR (95 % CI)*	No. cases/controls	Adjusted OR (95 % CI)*
CC + CA	58/140	1.00	101/139	1.82 (1.21 − 2.75)
AA	28/38	1.87 (1.03 − 3.36)	42/40	2.66 (1.55 − 4.59)
P for multiplicative interaction = 0.55
Measures of additive interaction^†
Relative excess risk due to interaction (RERI) = −0.02 (95 % CI: -1.63 − 1.59)
Attributable proportion due to interaction (AP) = −0.01 (95 % CI: -0.61 − 0.60)
Synergy index (S) = 0.99 (95 % CI: 0.38 − 2.58)

*Adjusted for sex, age, region of residence, and smoking.
^†Statistically significant when the 95 % CI of RERI > 0, the 95 % CI of AP > 0, or the 95 % CI of S > 1, indicating additive interaction.

ISSN: 1471-2377