Four-year changes in central fatness, risk of diabetes, and metabolic control in older adults: a cohort study with mediation analysis

Abstract

Background/aims: Older adults are vulnerable to central obesity, while the association of changes in central fatness with risk of diabetes and metabolic control has not been investigated among this particular population. This study was aimed to address these issues.

Methods: A total of 1,815 adults aged ≥ 60 years without diabetes at baseline were followed for 4 years. Incident diabetes was ascertained based on plasma glucose, hemoglobin A1c, medical history, and/or the use of anti-diabetic drugs. Central fatness was assessed by waist circumference (WC), waist-height ratio (WHtR), and body roundness index (BRI). Logistic regression analyses were used to assess the association of changes in central fatness with risk of diabetes, along with dose-response and mediation analyses.

Results: During the 4-year follow-up, 177 participants developed diabetes. The risk of diabetes was increased by 42%, 41%, and 40% per 1 standard deviation increases in WC, WHtR, and BRI, respectively, in multivariable-adjusted models (all p < 0.01). Moreover, these relationships were all linearly-shaped (all pnonlinearity ≥ 0.11). Increases in WC, WHtR, and BRI correlated with increases in hemoglobin A1c, triglycerides-and-glucose index, triglycerides, white blood cell, and C-reactive protein (all p ≤ 0.04). Yet only changes in hemoglobin A1c and triglycerides-and-glucose index were identified as the possible mediators for risk of diabetes, with their mediating effect being about 35% and 21%, respectively.

Conclusion: Increases in central fatness were related to elevated risk of diabetes, and this association might be partly explained by the worsening of glycemic control and insulin resistance in older adults.

Keywords: Aged; Follow-up studies; Insulin resistance; Mediation analysis; Obesity.

Figure 1

Dose-response analyses. (A) Dose-response analysis for changes in waist circumference, (B) dose-response analysis for changes in waist-height ratio, and (C) dose-response analysis for changes in body roundness index. All dose-response analyses were modeled with the restricted cubic splines with 3 knots at 10, 50, and 90 percentiles, and controlled for age, sex, body mass index, history of smoking and drinking (yes or no), systolic blood pressure, total cholesterol/high-density lipoprotein cholesterol, uric acid, C-reactive protein, and walking speed at baseline. OR, odds ratio; CI, confidence interval.

Figure 2

Mediation analysis for risk of diabetes associated with changes in central fatness and risk of diabetes. SBP, systolic blood pressure; DBP, diastolic blood pressure; FPG, fasting plasma glucose; HbA1c, hemoglobin A1c; TyG, triglycerides-and-glucose; TC, total cholesterol; TG, triglycerides; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; WBC, white blood cell; CRP, C-reactive protein; GSEM, generalized structural equation model; WC, waist circumference; WHtR, waist-height ratio; BRI, body roundness index.