Lower-income individuals under age 65 who have diabetes have a much higher risk of death than older and more affluent people with the disease, according to an Ontario study that suggests 65-and-over universal drug coverage extended to all age groups could help close the health gap between rich and poor.

Mortality rates of people with diabetes have fallen substantially due largely to better drug therapy, according to research by scientists at the Institute for Clinical Evaluative Sciences (ICES) and St. Michael’s Hospital in Toronto.

"However, trends have been less favourable among those of lower socioeconomic status (SES), leading to a widening gap in mortality between rich and poor," says the study. Titled "Universal drug coverage and socioeconomic disparities in diabetes outcomes,” it was released Monday in the publication Diabetes Care.

The population-based cohort study assessed the administrative health claims of 606,051 people with diabetes in the province between April 1, 2002, and March 31, 2008. Their socioeconomic status was based on their neighbourhood median household income levels from the 2001 Canadian census.

The study found that socioeconomic status was a strong predictor of death and non-fatal heart attack or stroke among 65-and-under individuals, but not among seniors.

In fact, it adds, the wage gap is leading to a 51 per cent higher risk of dying for those with lower socioeconomic status. A year after a heart attack, younger people in the lowest income category had 33 per cent higher rates of death one year later, compared to people the same age in the highest income category.

“From our observations, as many as 5,000 deaths and nearly 2,700 heart attacks or strokes could have been avoided among younger and middle-aged adults with diabetes if the gap between wealthier and poorer individuals had been identical to that seen among older groups,” St. Michael's Hospital endocrinologist Dr. Gillian Booth, the study's lead author and an ICES scientist, says in a news release.

Worldwide, more than 350 million people have diabetes – a chronic disease where the body is unable to produce or use the hormone insulin properly — and that figure is expected to double in the coming decades with the dramatic rise in obesity and the aging population, Booth and the other researchers note in the study. In Canada, more than 2.4 million Canadians have been diagnosed with the disease, according to the Public Health Agency of Canada.

Costs of diabetes drugs rising

While prescription drugs are funded publicly in the various provinces and territories for subpopulations such as people 65 and over, there is no universal publicly funded plan in Canada, although some advocacy groups have been lobbying for a national program.

In the case of diabetes, the cost of more effective drug regimens has risen considerably over the past decade, and the gap in mortality between richer and poorer patients with diabetes has widened in that time, according to the ICES study.

“We found that younger and middle-aged people with diabetes [under-65s] seem to be more susceptible to the effects of income,” said Booth.

The study cites recent studies suggesting that escalating drug costs may have a negative impact on diabetes care for low-income groups without proper insurance coverage.

"These people are more likely to restrict their use of prescription medications because of high out-of-pocket costs, and this in itself is associated with poorer health outcomes," the study says. "Lower-income groups share a disproportionate burden of diabetes, experience more complications from diabetes and are far less likely to have drug insurance.This is true even in Canada where health care is provided free of charge for all but prescription drugs are not a universal benefit."

Drug coverage helps health outcomes

The study's findings also suggest that publicly funded prescription drug coverage for Ontarians 65 and older (and for select populations under 65) may be a big reason for the socioeconomic disparity in health outcomes, and that providing this coverage for all age groups could potentially "help bridge the gap in cardiovascular risk and death between rich and poor groups with diabetes."

"A growing body of literature highlights the importance of health insurance in closing the gap in health outcomes between groups of differing socioeconomic status," the researchers write.

The study authors say the strengths of the study include its large size and its population-based sample, but add it has these limitations:

• No individual data on income, although neighbourhood income is a "widely used measure of SES that correlates well with individual-level measures."
• While universal access to drug benefits at age 65 could have accounted for age-related differences in the impact of SES on health outcomes, "we could not test this assertion directly, as our datasets lacked information on insurance coverage in younger groups."
• The researchers' databases lacked information on clinical variables such as blood pressure and cholesterol levels.
• No information on immigration status or ethnicity.

The research was funded by:

• The Project for an Ontario Women's Health Evidence-Based Report (POWER Study), which received funding from Echo: Improving Women’s Health in Ontario, an agency of the Ontario Ministry of Health and Long-Term Care.
• The Canadian Institutes of Health Research (CIHR).