Table 2.

Subgroup analysis results of included studies

Subgroup	No. of studies	Prevalence% (95% CI)	I2	P
Overall	18	0.28 (0.20, 0.37)	99.7	< 0.001
Sex				< 0.001
Male	18	0.205(0.137,0.282)	99.036
Female	18	0.339(0.264,0.419)	99.002
Age(years)				< 0.001
40–49	8	0.194 (0.089, 0.327)	97.826
50–59	14	0.206 (0.117, 0.311)	98.655
60–69	13	0.328 (0.214, 0.452)	98.643
70–79	6	0.297 (0.239, 0.358)	87.170
≥ 80	7	0.320 (0.209, 0.442)	94.789
BMI				< 0.001
< 24	6	0.233 (0.116, 0.375)	99.025
24 ≤ BMI < 28	6	0.446 (0.192, 0.716)	99.550
≥ 28	6	0.505 (0.290, 0.719)	98.124
Sampling Resources				< 0.001
Rural	1	0.242 (0.221, 0.265)
Urban	9	0.255 (0.202, 0.312)	96.943
Urban and rural	8	0.305 (0.172, 0.457)	99.756
Study Region				< 0.001
North China	11	0.294 (0.189, 0.412)	99.658
South China	7	0.249 (0.185, 0.318)	97.696
Altitude				< 0.001
High altitude area	5	0.444 (0.230, 0.669)	99.630
Low altitude area	13	0.218 (0.164, 0.277)	99.020

BMI Body mass index