Working-age adults with diabetes experience greater susceptibility to seasonal influenza: a population-based cohort study.

AIMS/HYPOTHESIS: The aim of this work was to compare the incidence of illness attributable to influenza in working-age adults (age <65 years) with and without diabetes.

METHODS: We performed a cohort study using administrative data from Manitoba, Canada, between 2000 and 2008. All working-age adults with diabetes were identified and matched with up to two non-diabetic controls. We analysed the rates of influenza-like illness physician visits and hospitalisations, pneumonia and influenza hospitalisations, and all-cause hospitalisations. Multivariable regressions were used to estimate the influenza-attributable rate of each outcome.

RESULTS: We included 745,777 person-years of follow-up among 166,715 subjects. The median age was 50-51 years and 48-49% were women; adults with diabetes had more comorbidities and were more likely to be vaccinated for influenza than those without diabetes. Compared with similar adults without diabetes, those with diabetes had a 6% greater (RR 1.06, 95% CI 1.02, 1.10; absolute risk difference 6 per 1,000 adults per year) increase in all-cause hospitalisations associated with influenza, representing a total of 54 additional hospitalisations. There were no differences in the influenza-attributable rates of influenza-like illness (p = 0.06) or pneumonia and influenza (p = 0.11).

CONCLUSIONS/INTERPRETATION: Guidelines calling for influenza vaccinations in diabetic, in addition to elderly, adults implicitly single out working-age adults with diabetes. The evidence supporting such guidelines has hitherto been scant. We found that working-age adults with diabetes appear more susceptible to serious influenza-attributable illness. These findings represent the strongest available evidence for targeting diabetes as an indication for influenza vaccination, irrespective of age.