Modifications of the homeostasis model assessment of insulin resistance index with age

The aim of the study was to analyze the association between aging and insulin resistance estimated by the homeostasis model assessment of insulin resistance (HOMA-IR). This work involved two studies: (1) the Di@bet.es study is a cross-sectional study including 4,948 subjects, comprising a representative sample of the adult Spanish population; (2) the Pizarra study is a population-based cohort study undertaken in Pizarra (Spain), in which 1,051 subjects were evaluated at baseline and 714 completed the 6-year follow-up study. Study variables included a clinical and demographic structured survey, a lifestyle survey, a physical examination, and an oral glucose tolerance test in subjects without diabetes. In the Di@bet.es study overall, an increase occurred in blood glucose until the age of 50, after which it remained stable (data adjusted for gender, body mass index, abnormal glucose regulation [AGR]). The HOMA-IR increased significantly with age (p = 0.01), due to a higher prevalence of obesity (p < 0.0001) and AGR (p < 0.001). In nonobese subjects without AGR, HOMA-IR values were not modified with age (p = 0.30), but they were with body mass index (p < 0.001). In the Pizarra study, the HOMA-IR was significantly lower after 6-year follow-up in the whole study population. Subjects with a HOMA-IR level higher than the 75th percentile at baseline were more likely to develop diabetes (OR 2.2, 95 % CI 1.2-3.9; p = 0.007) than subjects with a lower HOMA-IR. We concluded that age per se did not increase HOMA-IR levels, changes that might be related to higher rates of obesity and AGR in older subjects. The HOMA-IR was associated with an increased risk of developing type 2 diabetes 6 years later.