Prevalence of Abdominal Obesity in Chinese Middle-Aged and Older Adults with a Normal Body Mass Index and Its Association with Type 2 Diabetes Mellitus: A Nationally Representative Cohort Study from 2011 to 2018

Figures & data

Figure 1 Flowchart of study population.

Figure 2 The prevalence of abdominal obesity determined by waist circumference in subgroups of gender and age. (A). Prevalence of abdominal obesity defined by waist circumference in different genders. (B). Prevalence of abdominal obesity defined by waist circumference in different age groups.

Figure 3 Beeswarm plots of the distribution of waist circumference across the subgroups. (A). Beeswarm plots of the distribution of waist circumference grouped by gender. (B). Beeswarm plots of the distribution of waist circumference in T2DM patients and participants without T2DM.

Table 1 Characteristics of the Study Population

	General	Men	Women	P
Age, mean (SD), year	59.75 (9.32)	60.33 (9.10)	59.14 (9.51)	<0.001
Education Level, No. (%)				<0.001
Primary or Lower	3145 (72.3)	1451 (64.8)	1694 (80.3)
Secondary	1158 (26.6)	755 (33.7)	403 (19.1)
Higher	45 (1.0)	32 (1.4)	13 (0.6)
Rural Residence, No. (%)	3763 (86.6)	1964 (87.8)	1799 (85.3)	0.016
Alcohol drinking, No. (%)	772 (17.8)	709 (31.7)	63 (3.0)	<0.001
Smoke, No. (%)	1476 (34.0)	1360 (60.8)	116 (5.5)	<0.001
BMI, mean (SD), kg/m^2	21.5 (1.5)	21.4 (1.5)	21.6 (1.5)	<0.001
WC, mean (SD), cm	80.6 (6.7)	80.8 (6.4)	80.4 (7.0)	0.026
WHtR, mean (SD)	0.51 (0.05)	0.49 (0.04)	0.53 (0.05)	<0.001
SBP, mean (SD), mmHg	127.0 (21.2)	126.9 (20.2)	127.1 (22.2)	0.260
DBP, mean (SD), mmHg	73.4 (11.7)	74.0 (12.0)	72.7 (11.3)	0.002
TC, mean (SD), mmol/L	4.92 (0.95)	4.78 (0.92)	5.06 (0.97)	<0.001
TG, mean (SD), mmol/L	1.27 (0.77)	1.20 (0.74)	1.34 (0.80)	<0.001
LDL-C, mean (SD), mmol/L	2.90 (1.08)	2.79 (1.01)	3.01 (1.12)	<0.001
HDL-C, mean (SD), mmol/L	1.41 (0.39)	1.39 (0.40)	1.42 (0.37)	<0.001
HbA1c, mean (SD), %	5.07 (0.40)	5.07 (0.40)	5.08 (0.39)	0.601
Prediabetes, No. (%)	1901 (43.7)	1001 (44.7)	900 (42.7)	0.168

Notes: The data were expressed as means (standard deviation) for continuous variables and numbers (percentages) for categorical variables. P-value: from the Wilcoxon rank-sum test for skewed continuous variables and chi-square test for categorical variables.

Abbreviations: BMI, body mass index; DBP, diastolic blood pressure; HbA1c, glycated hemoglobin; HDL-C, high-density lipoprotein cholesterol; LDL-C, low density lipoprotein cholesterol; SBP, systolic blood pressure; TC, total cholesterol; TG, triglyceride; WC, waist circumference; WHtR, waist-to-height ratio.

Figure 4 The Kaplan-Meier unadjusted survival estimates for different waist circumference groups.

Table 2 Incidence of T2DM and Hazard Ratios (95% CI) of Waist Circumference in the Cox Proportional-Hazards Model

	Waist Circumference
	Normal	Increased	Substantially Increased
No of subjects	2705	902	741
No of T2DM cases	170	84	96
Person-years	17,180.6	5657.2	4436.2
Incidence rate (1000 person-year)	9.9	14.9	21.6
HR (95% CI)
Model 1	1.00	1.48 (1.13–1.93)	2.04 (1.56–2.67)
Model 2	1.00	1.46 (1.10–1.93)	2.01 (1.51–2.68)
Model 3	1.00	1.39 (1.05–1.84)	1.90 (1.42–2.54)
Model 4	1.00	1.39 (1.05–1.85)	1.89 (1.42–2.53)

Notes: Model 1: Adjusted for age, sex. Model 2: Included variables in model 1 and further adjusted for body mass index, district, educational level, smoking consumption, drinking status. Model 3: Adjusted for factors in model 2 plus systolic blood pressure, diastolic blood pressure, total cholesterol, triglycerides, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol. Model 4: Model 3 plus HbA_1c.

Abbreviations: HR, hazard ratio; T2DM, type 2 diabetes mellitus.

Table 3 Incidence of T2DM and Hazard Ratios (95% CI) of Waist Circumference for Different Subgroups in the Cox Proportional-Hazards Model

	Waist Circumference
	Normal	Increased	Substantially Increased
Men (n=2238)
No of subjects	1682	365	191
No of T2DM cases	104	36	22
Person-years	10,668.8	2256.2	1154.8
Incidence rate^a	9.7	16.0	19.1
HR (95% CI)	1.00	1.48 (0.98–2.23)	1.60 (0.97–2.66)
Women (n=2110)
No of subjects	1023	537	550
No of T2DM cases	66	48	74
Person-years	6511.8	3401.0	3281.4
Incidence rate^a	10.1	14.1	22.6
HR (95% CI)	1.00	1.29 (0.88–1.90)	1.96 (1.36–2.85)
Prediabetes (n=1901)
No of subjects	1149	402	350
No of T2DM cases	90	53	62
Person-years	7293.5	2476.9	2069.9
Incidence rate^a	12.3	21.4	30.0
HR (95% CI)	1.00	1.85 (1.27–2.69)	2.46 (1.67–3.61)
NGT (n=2447)
No of subjects	1556	500	391
No of T2DM cases	80	31	34
Person-years	9887.2	3180.3	2366.3
Incidence rate^a	8.1	9.7	14.4
HR (95% CI)	1.00	1.00 (0.64–1.55)	1.34 (0.85–2.11)

Notes: ^a1000 person-year. Model: adjusted for age, sex, body mass index, district, educational level, smoking consumption, drinking status, systolic blood pressure, diastolic blood pressure, total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and HbA_1c.

Abbreviations: HR, hazard ratio; NGT, normal glucose tolerance; T2DM, type 2 diabetes mellitus.

Figure 5 Sensitivity analyses using waist circumference to define abdominal obesity (A). Sensitivity analyses using Time-dependent Cox model. (B). Sensitivity analyses for participants with normal BMI throughout the follow-up (n=3451). (C). Sensitivity analyses for participants with more than 2 years of follow-up (n=4253).