. 2022 Dec 9;22:311. doi: 10.1186/s12902-022-01236-8

Table 2.

Descriptive characteristics of included studies and outcomes

Author	Type of outcome	Sub-type of outcome	Study type(s)	Total included studies	Total participants
Zhu et al. [28]	Mortality	All-cause mortality	Cohort	18	19,813
Xu et al. [5]		CVD mortality in all DR	Cohort	10	11,239
		CVD mortality in mild DR		4	7,361
		CVD mortality in severe DR		6	9,691
Zhu et al. [8]	Disease	Obstructive sleep apnoea	Case–control	6	1,092
Kjærsgaard et al. [35]		Primary open angle glaucoma	Cohort	2	241,037
Kjærsgaard et al. [35]		Primary open angle glaucoma	Cross-sectional	4	15,389
Shiferaw et al. [30]		Chronic kidney disease	Cohort	2	781
Song et al. [31]		Non-alcoholic fatty liver disease all DR	Cross-sectional	8	7,170
		Non-alcoholic fatty liver disease non-proliferative DR		3	3,977
		Non-alcoholic fatty liver disease proliferative DR		3	3,977
Wu and You [7]	Mental health	Depression (Type I)	Case–control	3	971
Zou et al. [29]		Depression (Type II)	Cross-sectional	9	31,766
Trott et al. [32]		Eating disorders	Cross-sectional and case–control	7	1,091
Chai et al. [33]		Dementia	Cohort	3	46,185
Chai et al. [33]		Alzheimer’s	Cohort	2	7,754
Wu et al. [34]		Cognitive impairment	Cross-sectional	5	2,451
Wu et al. [34]		Cognitive impairment	Cohort	5	1,397