Prevalent hyperglycemia in older obese population and age-dependent convergence of obese indices: Results of a cross-sectional study of Japanese generations over the adult life span.

PURPOSE/AIM: An age-dependent decline has been observed in the association between obesity and type 2 diabetes, a major comorbidity of obesity, although the evidence is limited. Therefore, we investigated the association and the plausible underlying mechanism in a large epidemiological study.

MATERIALS AND METHODS: We examined the association between the degree of obesity and hyperglycemia in five age groups (20-39, 40-49, 50-59, 60-69, and 70-85 years) in a cross-sectional study of 78,776 apparently healthy Japanese men and women who underwent a checkup in 2012. Hyperglycemia was defined as glycosylated hemoglobin (HbA1c) of ≥5.7% and/or pharmacotherapy for diabetes.

RESULTS: The incidence of hyperglycemia was three times higher in the 70-85-year-old group (62%) than in the 20-39-year-old group (20%) in obese individuals (body mass index [BMI] ≥ 27.0 kg/m(2)). However, the incidence was 12 times higher in reference-weight individuals (21.0-22.9 kg/m(2); 48% and 4%, respectively). As age increased, mean BMI and waist circumference approached certain non-obese ranges (22-24 kg/m(2) and 80-86 cm, respectively), even in hyperglycemic subjects. Logistic regression analysis revealed an age-dependent decline in the association between obesity and hyperglycemia, relative to that in reference-weight individuals.

CONCLUSIONS: Our results confirmed the previously reported age-dependent decline in the association between obesity and hyperglycemia, although hyperglycemia was still prevalent in older obese subjects than in older reference-weight subjects. Therefore, the decline in the association may be accelerated due to an age-dependent increase in the prevalence of hyperglycemia in reference-weight individuals.