Effects of age on insulin resistance and secretion in subjects without diabetes.

OBJECTIVE: To examine whether aging itself affects insulin resistance (IR) and insulin secretion in the general Japanese population.

METHODS: This study included data for 2,324 men and 1,472 women 30-79 years of age without diabetes who participated in a general health checkup program. The effects of age on homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of β-cell function (HOMA-B) were examined using a linear regression model. Logistic regression models were used to identify clinical characteristics related to age. Multiple regression analyses using a stepwise form were performed to examine factors, including age, possibly affecting HOMA-IR and HOMA-B.

RESULTS: The fasting plasma glucose (FPG) levels increased with age in both sexes, whereas the body mass index (BMI) and HOMA-B decreased with increasing age in men and the BMI increased with age in women. The HOMA-IR increased with increasing age in postmenopausal women. The proportion of physically active subjects increased in both sexes, and the proportion of current smokers decreased with age in men and postmenopausal women. The proportion of regular drinkers increased, and the proportion of subjects with a family history of diabetes decreased with age in men. The stepwise multiple regression analysis showed that age was inversely associated with the HOMA-B in both sexes and positively associated with the HOMA-IR in men and postmenopausal women. However, the BMI had the largest impact on the HOMA-IR and HOMA-B in both sexes.

CONCLUSION: Age-related increases in the glucose levels in Japanese men and women may be associated with impaired insulin secretion. As a result, a sex difference was observed regarding the impact of aging on IR.