Table 4. Analyses Stratified By Adherence Measure, Study Location, Design and Power.

	k	OR	(95% CI)	p	I2	Heterogeneity test
Necessity
UK study	32	2.201	1.786–2.713	<0.001	72.72%***	Q(1) = 7.67, p<0.05
Non-UK study	64	1.573	1.405–1.761	<0.001	74.79%***
Concerns
UK study	31	0.403	0.335–0.485	<0.001	62.75%***	Q(1) = 7.61, p<0.05
Non-UK study	62	0.555	0.486–0.635	<0.001	82.48%***
Necessity
Subjective adherence measure	83	1.737	1.565–1.929	<0.001	75.54%***	Q(1) = 0.031, p = 0.86
Objective adherence measure	13	1.817	1.114–2.963	0.017	86.20%***
Concerns
Subjective adherence measure	81	0.485	0.429–0.549	<0.001	82.84%***	Q(1) = 13.55, p<0.001
Objective adherence measure	12	0.726	0.609–0.866	<0.001	8.93%
Necessity
Prospective/longitudinal	18	1.526	1.243–1.874	<0.001	63.02***	Q(1) = 1.82, p = 0.18
Cross-sectional	78	1.798	1.595–2.027	<0.001	79.49%***
Concerns
Prospective/longitudinal	18	0.449	0.356–0.567	<0.001	70.88%***	Q(1) = 1.14, p = 0.29
Cross-sectional	75	0.519	0.458–0.588	<0.001	81.28%***
Necessity
Low power	18	1.848	1.290–2.646	0.001	46.19%*	Q(1) = 0.12, p = 0.73
High power	78	1.730	1.550–1.930	<0.001	80.16***
Concerns
Low power	17	0.488	0.371–0.643	<0.001	0.00%	Q(1) = 0.05, p = 0.82
High power	76	0.505	0.448–0.570	<0.001	83.83%***

Note. *p<.05, ***p<.001 for Q statistic.