Diabetes Diagnosis More Likely in Lower-Income Groups

January 16, 2013

The rate of new diabetes diagnosis is inversely related to income, a new Canadian study has shown. "There was a 20% higher risk of diabetes in the lowest 2 income groups compared with the highest group, which translated into an extra 2500 diagnoses of diabetes for that year," senior author of the research, Lorraine Lipscombe, MD, from the University of Toronto, Ontario, told Medscape Medical News. "Diabetes rates are increasing dramatically across all groups, and what we are finding is that those who are most socially disadvantaged are experiencing the greatest burden," she added.

Many previous studies have looked at the prevalence of diabetes across income groups, but the effect of income on diabetes incidence — actual new diagnosis — is less well understood, say Zoe Lysy, MD, from the University of Toronto, and colleagues in their paper, published online January 10 in Diabetes Research and Clinical Practice. "We were isolating the risk more than the prevalence," Dr. Lipscombe noted. "We also looked at whether these disparities could be explained by differences in diabetes screening, and we did not see that, so this is more a reflection of true risk," she said.

The researchers divided the figures into age and gender groups, too, and found that women and younger people in low-income groups were most vulnerable.

Diabetes rates are increasing dramatically across all groups, and those who are most socially disadvantaged are experiencing the greatest burden. Dr. Lorraine Lipscombe

Dr. Lipscombe said that there are messages from this work for physicians and policymakers. "Interventions targeted toward more socially disadvantaged populations to help them reduce their risk of diabetes would be important.

"We found no differences in screening across income groups, but physicians should be aware that lower-income groups may be at higher risk of diabetes and ensure that they are getting screening early and being offered early preventive counseling if they have risk factors.

"We know from previous work that once lower-income populations get diabetes, they have worse outcomes, and this is a bigger problem in the younger population than the older one. So we also need greater attention to issues such as access and affordability of diabetes medications and access to diabetes education services once people get diabetes."

Socioeconomic Factors More Salient in Younger Populations?

Lysy and colleagues used a population-based diabetes registry and census data from Ontario. They compared rates of new diabetes cases among persons aged 20 years and older between April 1, 2006, and March 31, 2007, between neighborhood income quintiles and assessed for age- and sex-based differences.

The majority of diabetes would have been type 2, given that they examined an adult population, Dr. Lipscombe said, but she noted that they were unable to distinguish between types 1 and type 2 because the database just lists diabetes. "We may have picked up some new type 1 diabetes diagnosis between the age of 20 and 30," she noted.

We think the socioeconomic factors that increase one's risk for diabetes are more salient in the younger groups, whereas these factors might be offset by the effect of aging in the older groups. Dr. Lorraine Lipscombe

There were 88,886 new cases of diabetes during the study period (incidence rate 8.26/1000). Increasing income quintile was associated with a significantly lower diabetes incidence (8.70/1000 in the lowest quintile vs 7.25/1000 in the highest quintile; P < 0.0001).

The income-based gap in incident diabetes was more pronounced in the younger compared with the older age groups, as evidenced by rate ratios between the lowest and highest income quintiles of 1.55 and 1.38 for ages 20 to 39 years and 40 to 59 years, respectively, compared with 1.20 and 1.21 for ages 60 to 79 years and 80 years and older, respectively.

Dr. Lipscombe stressed, however, that the "absolute risk" of diabetes was higher in the older age groups. "What we think — and this is just speculation, because our study did not look at reasons — is that the socioeconomic factors that increase one's risk for diabetes are more salient in the younger groups, whereas these factors might be offset by the effect of aging in the older groups," she noted.

And while income had a minimal effect on the incidence of diabetes in older men, the impact of low income on risk of diabetes persisted across all age groups in women.

Greater Diabetes-Prevention Efforts Targeted to Young and Poor

Dr. Lipscombe said that, based on prior research, issues such as "higher rates of obesity, poorer diets, a more sedentary lifestyle, affordability of and accessibility to healthy food options and opportunities for physical exercise, as well as health literacy, may all play a role" in the discrepancies observed. And there may also be an effect of immigration. Ontario, for example, has seen a large increase in immigration from populations at higher risk for diabetes, such as South Asians, over the past decade, and immigrants are often of lower socioeconomic status when they first arrive, she noted.

"It will be important to look at these factors more closely to see to what extent they contribute," she said. "Greater diabetes-prevention efforts need to be directed toward younger, low-income populations to lessen the lifelong burden of diabetes on the health and productivity of an already-disadvantaged population."

The authors have disclosed no relevant financial relationships.

Diabetes Res Clin Pract. Published online January 10, 2013. Abstract