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The baseline characteristics of the follow-up population are shown in Table 1. A total of 2,892 individuals were recruited, and more than half of them were women (63.8%). Simultaneously, the women had a younger age, fewer school years, lesser personal monthly income, higher rural living percentage, higher smoking status, higher alcohol-drinking status, hypertension, higher BMI, lower FPG and UA median, and higher 2 h PG results compared with men (P all < 0.05). After 3.0 years of follow-up, 114 men (10.9%) and 172 women (9.3%) were diagnosed with T2DM.
Characteristics Men Women P-value Number, (%) 1,046 (36.2) 1,846 (63.8) < 0.001 Age, (years) 52.1 ± 11.0 50.3 ± 9.7 < 0.001 School years > 9, n (%) 255 (24.4) 365 (19.8) 0.003 Unmarried, n (%) 58 (5.6) 86 (4.7) 0.286 Rural living, n (%) 867 (82.9) 1,410 (76.4) < 0.001 Personal monthly income, n (%) < 0.001 ≤ 599 476 (46.9) 1,113 (62.7) 600–1,999 435 (42.9) 621 (35.0) ≥ 2,000 103 (10.2) 41 (2.3) Family history of diabetes, n (%) 105 (10.3) 210 (11.5) 0.318 T2DM in the follow-up survey, n (%) 114 (10.9) 172 (9.3) 0.171 Follow-up duration (years) 3.14 3.19 0.174 Current smoking, n (%) 594 (57.1) 62 (3.4) < 0.001 Current alcohol-drinking status, n (%) 449 (43.1) 16 (0.9) < 0.001 BMI (kg/m2) 24.9 ± 3.4 25.5 ± 3.6 < 0.001 Hypertension, n (%) 518 (50.0) 802 (43.9) 0.002 TG (mmol/L) 1.03 (0.74, 1.56) 1.08 (0.77, 1.60) 0.267 TC (mmol/L) 5.16 (4.58, 5.77) 5.14 (4.56, 5.83) 0.843 FPG (mmol/L) 5.6 (5.2, 6.1) 5.5 (5.1, 5.9) < 0.001 2 h PG (mmol/L) 6.2 (5.1, 7.5) 6.5 (5.6, 7.7) < 0.001 HDL-C (mmol/L) 1.57 (1.34, 1.87) 1.60 (1.38, 1.85) 0.059 UA (μmol/L) 341 (294, 395) 267 (228, 311) < 0.001 Note. BMI, body mass index; T2DM, type 2 diabetes mellitus; TG, triglycerides; TC, total cholesterol; FPG, fasting plasma glucose; 2 h PG, 2-hour post-load plasma glucose; HDL-C, high-density lipoprotein cholesterol; UA, uric acid. Table 1. Baseline characteristics of the follow-up population
As shown in Figure 2, higher TG at baseline indicated significantly increased T2DM incidence in women (Ptrend < 0.001) but not in men (P = 0.101). However, higher TC showed significantly increased T2DM incidence in both men (Ptrend = 0.029) and women (Ptrend < 0.001).
Figure 2. The incidence (%) of type 2 diabetes mellitus in men and women based on the triglycerides (TG) and total cholesterol (TC) levels
Cox regression results were presented in Table 2. Univariate Cox regression showed that higher TG [BHTG (HR: 2.05; 95% CI: 1.40, 3.00), hypertriglyceridemia (HR: 2.64; 95% CI: 1.68, 4.15)] and TC [hypercholesterolemia (HR: 2.05; 95% CI: 1.43, 2.95)] were significantly associated with increased risk of T2DM incidence in women but not in men. Only elevated TC [BHTC (HR: 1.61, 95% CI: 1.04, 2.48)] showed increased risk of T2DM in men even after adjusting for age, BMI, family history of diabetes, school years, marital status, geographic division, personal monthly income, smoking status, alcohol-drinking status, hypertension, HDL-C, and UA. Elevated TG [(hypertriglyceridemia (HR: 1.78; 95% CI: 1.07, 2.97)] and TC [hypercholesterolemia (HR: 1.68; 95% CI: 1.81, 2.61)] still indicated significant association in women in multivariate Cox regression analysis.
Varaibles N Model 1 Model 2 Men Triglycerides (mmol/L) < 4.1 817 1.00 1.00 4.1–4.9 110 1.12 (0.63, 2.02) 1.21 (0.64, 2.31) ≥ 4.9 119 1.42 (0.85, 2.37) 1.77 (0.97, 2.97) Total cholesterol (mmol/L) < 5.2 532 1.00 1.00 5.2–6.2 366 1.49 (1.00, 2.24) 1.61 (1.04, 2.48) ≥ 6.2 148 1.54 (0.91, 2.61) 1.44 (0.82, 2.52) Women Triglycerides (mmol/L) < 4.1 1,434 1.00 1.00 4.1–4.9 255 2.05 (1.40, 3.00) 1.29 (0.84, 1.99) ≥ 4.9 157 2.64 (1.68, 4.15) 1.78 (1.07, 2.97) Total cholesterol (mmol/L) < 5.2 969 1.00 1.00 5.2–6.2 586 1.09 (0.76, 1.56) 0.93 (0.62, 1.39) ≥ 6.2 291 2.05 (1.43, 2.95) 1.68 (1.81, 2.61) Note. Model 1: univariate Cox regression. Model 2: adjusted for age, body mass index (BMI), family history of diabetes, school years, marital status, geographic division, personal monthly income, smoking status, alcohol-drinking status, hypertension, high-density lipoprotein cholesterol (HDL-C), and uric acid (UA). HR, hazard ratio; 95% CI, 95% confidence interval. Table 2. HR and 95% CI of triglycerides and total cholesterol for type 2 diabete mellitus incidence in men and women in Cox regression models
AUROCs of TG and TC for T2DM incidence are presented in Figure 3. AUROCs of TG and TC in women were 0.60 (0.58–0.62) and 0.59 (0.56–0.61), respectively, with P < 0.001, and P > 0.05 for men. But the AUROCs of TG and TC predicting T2DM incidence were not significantly different in men and women.
Figure 3. Receiver operating characteristic (ROC) of triglycerides (TG), total cholesterol (TC) predicting type 2 diabetes mellitus (T2DM) incidence in men and women
The optimal cutoff values, sensitivity, specificity, and accuracy of actually identifying subjects with type 2 diabetes for TG and TC are presented in Table 3. The optimal cutoff values of TG and TC were > 1.15 and > 5.17 mmol/L in men, respectively, with low sensitivity [TG: 53.5% (43.9%, 62.9%) TC: 60.5% (50.9%, 69.6%)], low specificity [TG: 58.6% (55.3%, 61.8%); TC: 52.0% (48.8%, 55.3%)], and minimal practical utility [LR+: TG, 1.29 (1.10, 1.60) and TC, 1.26 (1.10, 1.50); LR−: TG, 0.79 (0.60, 1.00) and TC, 0.76 (0.60, 1.00)]. The cutoff values of TG and TC in women were the same as in men with low sensitivity, specificity, and minimal practical utility.
Items AUROC Cut off (mmol/L) Sensitivity (95% CI) Specificity (95% CI) LR+ (95% CI) LR− (95% CI) Men TG 0.54 (0.51, 0.58) > 1.15 53.51 (43.9, 62.9) 58.58 (55.3, 61.8) 1.29 (1.10, 1.60) 0.79 (0.60, 1.00) TC 0.55 (0.52, 0.58) > 5.17 60.53 (50.9, 69.6) 52.04 (48.8, 55.3) 1.26 (1.10, 1.50) 0.76 (0.60, 1.00) Women TG 0.60 (0.58, 0.62) > 1.23 58.14 (50.4, 65.6) 61.65 (59.3, 64.0) 1.52 (1.30, 1.70) 0.68 (0.60, 0.80) TC 0.59 (0.57, 0.61) > 5.77 41.28 (33.8, 49.0) 75.15 (73.0, 77.2) 1.66 (1.40, 2.00) 0.78 (0.70, 0.90) Note. AUROC, area under receiver operating characteristic; T2DM, type 2 diabetes mellitus; 95% CI, 95% confidence interval; LR+, positive likelihood ratio; LR–, negative likelihood ratio. Table 3. AUROC, optimal cutoff value (mmol/L), sensitivity (%), specificity (%), and accuracy of actually identifying subjects with T2DM