. Author manuscript; available in PMC: 2022 Jun 21.

Published in final edited form as: J Parkinsons Dis. 2022;12(1):267–282. doi: 10.3233/JPD-212851

Table 1.

Effect of genetically-predicted smoking on PD

Exposure	Odds ratio (95% Cl)	P

Smoking initiation (per 1-SD increase in the prevalence of ever smoking)
IVW (p-heterogeneity = 0.39)	0.74 (0.60–0.93)	0.009
Weighted median	0.64 (0.47–0.89)	0.008
Weighted mode	0.58 (0.24–1.42)	0.23
MR Egger (p-pleiotropy = 0.59; I²_GX = 0.66)	0.59 (0.24–1.45)	0.25
Corrected MR Egger	0.56 (0.22–1.39)	0.26
MR-PRESSO (p-pleiotropy = 0.24)	-	-
Lifetime smoking index (per l-unit)^a
IVW (p-heterogeneity = 0.007)	0.54 (0.29–1.00)	0.050
Weighted median	0.37 (0.16–0.84)	0.017
Weighted mode	0.29 (0.06–1.34)	0.12
MR Egger (p-pleiotropy = 0.93; I²_GX = 0.64)	0.60 (0.05–6.77)	0.68
Corrected MR Egger	0.60 (0.06–6.47)	0.68
MR-PRESSO (p-pleiotropy = 0.010, p-distortion = 0.77)^b	0.51 (0.29–0.89)	0.021

Cl, confidence interval; IVW, inverse variance weighted.

In the UK Biobank, the lifetime smoking index had a mean of 0.359 and a standard deviation (SD) of 0.694; a 1-SD increase in the lifetime smoking index is equivalent to an individual smoking 20 cigarettes a day for 15 years and stopping 17 years ago or an individual smoking 60 cigarettes a day for 13 years and stopping 22 years ago. The OR_IVW for a 1-SD increase is 0.67^0.694 =0.76.

Outliers: rs202645.