Table 2.

Subgroup analyses according to study design

Study design	Factors	Group	OR and 95%CI	P value	Heterogeneity (%)	P value for Q test	P value between subgroups
Cohort studies	Countries	Western	1.04 (0.70–1.53)	0.855	50.5	0132	0.318
		Eastern	0.77 (0.30–2.03)	0.603	73.9	0.050
	Publication year	Before 2010	0.87 (0.42–1.80)	0.703	75.3	0.018	0.722
		2010 or after	0.96 (0.76–1.23)	0.771	0.0	0.416
	Population	T2DM	0.96 (0.76–1.23)	0.771	0.0	0.416	0.086
		Mixed	1.15 (0.52–2.54)	0.722	69.7	0.069
		General	0.48 (0.25–0.93)	0.030	–	–
	Adjusted status	Yes	0.77 (0.53–1.11)	0.162	41.3	0.182	0.024
		No	1.52 (0.96–2.42)	0.076	0.0	0.540
	Study quality	High	0.77 (0.53–1.11)	0.162	41.3	0.182	0.024
		Low	1.52 (0.96–2.42)	0.076	0.0	0.540
Case control studies	Countries	Western	0.97 (0.75–1.24)	0.792	76.5	0.014	0.729
		Eastern	0.88 (0.26–2.95)	0.836	–	–
	Publication year	Before 2010	0.71 (0.36–1.41)	0.332	64.9	0.058	0.086
		2010 or after	1.11 (1.04–1.18)	0.001	–	–
	Population	T2DM	1.10 (1.03–1.16)	0.003	0.0	0.490	0.007
		Mixed	0.36 (0.16–0.81)	0.014	–	–
	Adjusted status	Yes	1.11 (1.04–1.18)	0.001	0.0	0.707	0.093
		No	0.65 (0.24–1.72)	0.383	82.4	0.017
	Study quality	High	1.11 (1.04–1.18)	0.001	–	–	0.086
		Low	0.71 (0.36–1.41)	0.332	64.9	0.058
Cross-sectional studies	Countries	Western	0.79 (0.61–1.03)	0.080	46.9	0.130	0.088
		Eastern	1.11 (0.77–1.58)	0.583	0.0	0.599
	Publication year	Before 2010	0.85 (0.60–1.20)	0.354	62.0	0.105	0.532
		2010 or after	0.87 (0.61–1.24)	0.451	48.4	0.121
	Population	T1DM	0.85 (0.67–1.08)	0.187	33.5	0.223	0.896
		T2DM	0.79 (0.36–1.77)	0.573	82.2	0.018
		Mixed	0.96 (0.51–1.81)	0.900	–	–
	Adjusted status	Yes	0.80 (0.59–1.10)	0.170	54.4	0.087	0.144
		No	1.01 (0.75–1.35)	0.973	00	0.718
	Study quality	High	0.73 (0.58–0.91)	0.006	–	–	0.114
		Low	0.92 (0.70–1.20)	0.538	36.9	0.175