Income related to higher incidence of diabetes in women and adults under 40

10/01/2013

A large, population-based study by researchers at the Institute for Clinical Evaluative Sciences (ICES) and Women’s College Research Institute (WCRI) 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.

Diabetes rates are increasing dramatically, and certain populations are at greater risk. Low income status is associated with higher diabetes prevalence and higher mortality, yet the effect of income on diabetes incidence is less well understood.

Lead author and ICES scientist Lorraine Lipscombe said, “This study found a significantly higher incidence of diabetes among lower income groups that was not accounted for by differences in diabetes testing.” The income-based gap was also greater among younger (under age 40 years) compared to older persons. In younger persons, the relative risk of diabetes was 1.5 times that of wealthier patients of the same age, whereas this difference narrowed in persons over age 60 years. In addition, the impact of low income on risk of diabetes persisted across all age groups in women.

Lipscombe, a staff physician in endocrinology at Women’s College Hospital, also noted that the findings are consistent with other studies that have shown an inverse association between socio-economic status and diabetes rates, however, this study demonstrates a disparity in new diabetes diagnoses that has implications both for future resource allocation and preventive strategies.

“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,” said Lipscombe.

The study examined the rate of new diabetes diagnoses among Ontarians aged 20 years or older between April 1, 2006 and March 31, 2007 using de-identified data from diabetes databases and census data and found that:

There were 88,886 new cases of diabetes during the study period
Rates of new diabetes diagnoses are higher among lower income populations
The income gap was wider among younger (20-59 years) compared to older persons
The effect of income on the risk of diabetes was also more pronounced among females compared to males

BACKGROUND:

The prevalence of diabetes has surged over the last 10 years. The World Health Organization predicts that 366 million people worldwide will have diabetes by 2030. The implications of this trend on the healthcare system are considerable, given the comprehensive care and cost involved in managing diabetes and its complications. The cost of these complications was estimated to be near 9 billion Canadian dollars annually in 2003.

Aging of the population and growing rates of obesity have contributed to the increasing incidence of type 2 diabetes in developed nations. Lower-income populations have a higher prevalence of diabetes and greater mortality, even in universally-funded healthcare settings. Moreover, our previous work showed that the income gap in mortality has widened over the last decade among patients with diabetes in Canada. This trend was most pronounced among persons under the age of 65, who do not have access to universal drug coverage.

The study, “The impact of income on the incidence of diabetes: a population-based study,” was published online today in Diabetes Research and Clinical Practice.

Author block: Lysy Z, Booth GL, Shah BR, Austin PC, Luo J, Lipscombe LL.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.

Women’s College Research Institute (WCRI), part of Women’s College Hospital, is dedicated to developing medical insights that enhance the health of women and improve health-care options for all. Fully affiliated with the University of Toronto, WCRI scientists lead research that translates into better clinical care that impacts people in Toronto, across Canada and around the world. For more information about how Women’s College Research Institute is transforming patient care, visit women's college research website.