New Evidence: Diabetes Does Up Risk for Flu-Related Illness

Nancy A. Melville

January 27, 2014

Adults with diabetes show a significantly greater risk for serious illness related to influenza compared with those without diabetes, justifying existing guidelines that call for influenza vaccination in the adult diabetic population, according to new research published online January 24 in Diabetologia.

Working-age adults (under 65 years of age) with diabetes are included in most guidelines for influenza vaccination, including those of the American Diabetes Association and the Canadian Diabetes Association. But research supporting this recommendation is surprisingly limited, and this new study is 1 of only 2 to have followed people with and without diabetes and compared influenza-related outcomes, the researchers explain. In fact, they say their new study "is the strongest available evidence for targeting diabetes as an indication for influenza vaccination, irrespective of age.

"Our observation that working-age adults with diabetes experience a greater burden of influenza than similar nondiabetic adults provides a clinical justification for targeted anti-influenza interventions," they stress.

While the findings, perhaps unsurprisingly, support the recommendations to vaccinate diabetic patients, such studies are important in providing evidence beyond simple intuition, said lead author Jeffrey A. Johnson, PhD, from the University of Alberta School of Public Health, Edmonton.

"It makes intuitive sense to say people with diabetes or other chronic diseases would be at increased risk of getting influenza, so we should target them for vaccination," he told Medscape Medical News. But "intuition has often been proven wrong…and it is better to do the studies and generate the best evidence we can."

Only Study to Have Adjusted for Comorbidities

The cohort study involved 166,715 subjects tracked with administrative data in Manitoba, Canada, from 2000 to 2008. The subjects' mean age was 52.5 years, and 48.5% were female.

In matching working-age adults with diabetes (n = 56,513) with nondiabetic controls (n = 110,202), subjects with diabetes were found to have more comorbidities and were more likely to be vaccinated for influenza, compared with those without diabetes (P < .05).

Although the database did not specify whether the diabetes was type 1 or type 2, the researchers say the "vast majority" of the diabetes was likely type 2 in this adult population.

After researchers controlled for variables including age, sex, socioeconomic status, location of residence, comorbidities, and vaccination, the adults with diabetes had a 6% increase in all-cause hospitalizations that were associated with influenza (RR 1.06; P = .044).

"Ours is the only study to have adjusted for comorbidities, vaccination status, and cyclic trends apart from influenza," the researchers say. "Compared with working-age nondiabetic adults, working-age adults with diabetes experienced a significantly greater 6% increase in influenza-attributable all-cause hospitalizations," they note.

No significant differences were seen between the diabetes and nondiabetes groups in rates of flulike illness or pneumonia and influenza per se, however, which the authors speculate was due to the increased need for hospitalization among diabetics.

"We infer that adults with diabetes experience a disproportionately greater susceptibility to more serious manifestations of influenza, requiring hospitalization," they state.

And the researchers point out that their data are limited to healthcare use, "which may underrepresent the total burden of influenza." Many working-age adults with influenza "do not present for medical attention, although they may still incur absenteeism and productivity losses."

Rates of Flu Vaccination Low Among Whole Cohort

Dr. Johnson also noted that, despite the recommendations for vaccination of people with diabetes, only 16% of diabetic adults had been vaccinated in the study. And only 7% of nondiabetics had received the flu vaccination.

"This difference was controlled for in our analysis, but in either case, it was very low use," he said.

He and his colleagues call for further studies to better understand the true effectiveness of the flu vaccine, arguing that even if effectiveness were as low as 20%, the benefits in avoiding the costs associated with influenza-related hospitalization would still be worthwhile.

"There are recommendations for the elderly and people with diabetes to get vaccinations, but the evidence for vaccine effectiveness is actually quite weak and is based (mainly) on epidemiologic and observational studies," Dr. Johnson said.

"This is why we call for randomized controlled trials on that question," he concluded.

The study received funding from the Canadian Institutes of Health Research. The authors have reported no relevant financial relationships.

Diabetologia. Published online January 24, 2014. Article

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