Clustering of protective factors for glucose intolerance and insulin resistance: A cross-sectional study

Aims: A cluster of interrelated factors: a body mass index (BMI) < 25 kg/m², moderate exercise and alcohol intake, non-smoking and a favourable dietary pattern has been linked with markedly reduced risk of Type 2 diabetes. The aim of this study was to estimate the prevalence of a similar low-risk group in a sample of middle-aged Irish men and women, and determine whether this cluster is associated with a reduced risk of glucose intolerance (IFG and Type 2 diabetes according to ADA/WHO criteria) and insulin resistance [homeostasis model assessment (HOMA) score in upper quartile of distribution]. 

Methods: A cross-sectional study involving a stratified random sample of 1018 general practice patients, aged 50-69 years. We defined a low-risk group based on the following variables: BMI < 25 kg/m²; waist-hip ratio < 0.85 for women and 0.90 for men; never smoking status; participation in medium to high level of physical activity; light drinking (3.5-7 units of alcohol per week) and a 'prudent' dietary pattern. Valid data were available for glucose tolerance status and HOMA score and all exposure variables from 684 and 671 participants, respectively. 

Results: A total of 7.5% of participants had none of the 'protective factors', 24.9% had one, 31.0% two, 23.3% three, 10.0% four, 3.0% five and 0.3% had six protective factors. In multivariate analyses the odds ratios for insulin resistance were 0.59, 0.48, 0.14 and 0.04 in persons with one, two, three and four or more low-risk factors, respectively, relative to those with none. Similar linear inverse trends were observed for glucose intolerance. 

Conclusions: The findings are consistent with an inverse linear relation between a cluster of core protective, lifestyle-related factors and the prevalence of both glucose intolerance and insulin resistance.