Table 3

Pooled risk estimates for Parkinson’s disease by exposure assessment method, study design, publication year period and geographic region, based on meta-analysis of articles on occupational pesticide exposure published between 1990 and 2020.

	Number of risk estimates	sRR	95% CI	Heterogeneity measures
	Number of risk estimates	sRR	95% CI	I² (%)	P value	Q	P value
Exposure assessment method						1.20	0.55
Group-level	6	1.34	1.16 to 1.54	0	0.54
Self-reported exposure	22	1.45	1.18 to 1.76	56	<0.01
Expert level	9	1.56	1.21 to 2.01	18	0.28
Study design						2.82	0.24
Cohort (prospective)	8	1.28	0.95 to 1.73	63	<0.01
Cohort (retrospective)	1	1.14	0.77 to 1.68	.	.
Case–control	28	1.54	1.34 to 1.77	27	0.09
Publication year period						1.49	0.22
1990–2006	19	1.58	1.32 to 1.89	36	0.06
2007–2020	18	1.34	1.12 to 1.62	48	0.01
Geographic region						1.92	0.38
Europe	14	1.47	1.21 to 1.79	37	0.08
USA	19	1.53	1.24 to 1.88	51	<0.01
Other	4	1.17	0.85 to 1.62	30	0.23
Case–control studies only
Exposure assessment method						0.60	0.74
Group-level	3	1.48	1.02 to 2.15	0	0.39
Self-reported exposure	20	1.51	1.24 to 1.83	42	0.02
Expert level	5	1.70	1.31 to 2.2	0	0.88
Exposure assessment method during publication year periods
1990–2006
Exposure assessment method						1.24	0.54
Group-level	3	1.57	1.09 to 2.27	37	0.20
Self-reported exposure	13	1.52	1.2 to 1.93	37	0.09
Expert level	3	2.38	1.12 to 5.03	28	0.25
2007–2020
Exposure assessment method						0.62	0.73
Group-level	3	1.23	0.93 to 1.62	0	0.83
Self-reported exposure	9	1.34	0.95 to 1.88	70	>0.01
Expert level	6	1.42	1.12 to 1.81	0	0.49

I²=percentage of variation across studies due to heterogeneity. Q=Cochran’s Q.
sRR, summary risk ratio.