Table 1.

Clinical and demographic characteristics of the study population.

Variables	Training set			Testing set
	DM/DR	DM	DR	DM/DR	DM	DR
Age, years	49/49	53.4 ± 9.4	58.0 ± 10.2	20/20	56.0 ± 12.0	57.0 ± 10.0
Gender, n/N
Male		29/49	26/49		9/20	10/20
Female		20/49	23/49		11/20	10/20
BMI, kg/m2	49/49	23.9 (22.1, 27.4)	24.1 (22.4, 27.0)	20/20	24.8 (23.1, 26.1)	25.2 (22.4, 26.2)
FPG, mmol/L	49/49	8.3 (6.9, 12.0)	8.9 (6.7, 10.9)	20/20	9.2 ± 2.7	7.8 ± 2.6
HbA1c, %	49/49	10.2 ± 2.4	9.7 ± 1.9	20/20	9.9 ± 2.0	10.3 ± 1.9
LDL, mmol/L	49/49	2.7 ± 0.9	2.6 ± 1.1	19/20	2.4 ± 1.2	2.5 ± 1.0
HDL, mmol/L	49/47	1.1 (0.8, 1.4)	1.1 (0.9, 1.4)	19/19	1.0 ± 0.3	1.0 ± 0.3
TG, mmol/L	49/49	1.6 (1.0, 2.1)	1.4 (1.0, 1.7)	19/20	1.8 (1.5, 2.4)	1.5 (1.1, 2.3)
TC, mmol/L	49/49	4.8 ± 1.1	4.6 ± 1.5	19/20	4.5 ± 1.3	4.3 ± 1.3
SBP, mmHg	49/49	125 ± 14	137 ± 20	20/20	135 ± 18	140 ± 25
DBP, mmHg	49/49	78 (73, 86)	76 (70, 80)	20/20	83 ± 10	81 ± 12
Duration of diabetes, years	41/44	8.1 ± 6.2	12.2 ± 6.1	14/19	9.9 ± 6.6	12.1 ± 7.8
Education, n/N
Junior high school or below		27/49	27/49		11/20	13/20
High school or above		22/49	22/49		9/20	7/20
Occupation, n/N
Manual workers		23/47	22/44		8/18	12/20
Mental worker		10/47	8/44		5/18	3/20
Both		14/47	14/44		5/18	5/20
History of diabetes, n/N
Yes		17/49	25/49		10/20	8/20
No		32/49	24/49		10/20	12/20
Smoking habits, n/N
Non-smokers		29/47	23/45		12/19	13/20
Current smokers		13/47	16/45		6/19	5/20
Ex-smokers		5/47	6/45		1/19	2/20
Alcohol consumption, n/N
Non-drinkers		22/47	20/45		11/19	9/20
Current drinkers		23/47	19/45		7/19	8/20
Ex-drinkers		2/47	6/45		1/19	3/20
Center, n/N
Wenzhou		24/49	33/49		12/20	15/20
Hefei		25/49	16/49		8/20	5/20

Continuous data obeying normal or similar normal distribution were described as mean ± standard deviation (s.d.) and the paired t-test was applied to compare the differences between the two groups. Otherwise, median (1st quartile, 3rd quartile) and Wilcoxon signed-rank tests were used. Categorical data were presented as n/N and McNemar–Bowker test was utilized to compare the differences of the cases and controls.

n, the number of exposed persons in each group; N, group size.

DBP, diastolic blood pressure; DM, type 2 diabetes (T2D) without diabetic retinopathy; DR, T2D with diabetic retinopathy; DM/DR= Number of DM and DR groups; FPG, fasting plasma glucose; HbA1c, glycated hemoglobin; HDL, high density lipoprotein; LDL, low density lipoprotein; TG, triglyceride; TC, total cholesterol; SBP, systolic blood pressure.