The impact of income on the incidence of diabetes: a population-based study.

AIMS: Diabetes rates are increasing dramatically, and certain populations are at greater risk. Low income status is associated with higher diabetes prevalence and higher mortality. The effect of income on diabetes incidence is less well understood.
METHODS: Using a validated, population-based diabetes registry and census data from Ontario, Canada, we compared the rate of new diabetes cases among persons aged 20 years or older between April 1st 2006 and March 31st 2007 between neighborhood income quintiles, and assessed for age- and sex-based differences.
RESULTS: There were 88,886 new cases of diabetes in Ontario adults during our study period (incidence rate 8.26/1000, 95% confidence interval, CI 8.20-8.31). Rates increased with age and were higher in males versus females. Increasing income quintile was associated with a significantly decreased diabetes incidence (8.70/1000, 95% CI 8.57-8.82 in the lowest quintile, vs. 7.25/1000, 95% CI 7.14-7.36 in the highest quintile, p<0.0001). Significant interactions were found between income quintile (1, 2, and 3 vs. 5) and age groups (20-39, 40-59 vs. 80+ years) (p<0.01) and sex (p<0.01), such that the impact of income was more pronounced in younger compared to older age groups and in females versus males. DISCUSSION: This population-based study found that diabetes risk is significantly higher in lower compared to higher income groups, and that this income gap was widest in younger persons and females. Greater diabetes preventive efforts directed toward younger and female lower-income populations are necessary, in order to lessen the lifelong burden of diabetes for an already disadvantaged population.