Higher frequency of hospitalization but lower relative mortality for pandemic influenza in people with type 2 diabetes

Higher frequency of hospitalization but lower relative mortality for pandemic influenza in people with type 2 diabetes:

Abstract

Background

There is limited evidence linking type 2 diabetes (T2D) to influenza‐related complications.

Objectives

To test a set of research questions relating to pandemic influenza vaccination, hospitalization and mortality in people with and without T2D.

Methods

In this population‐based cohort study, we linked individual‐level data from several national registers for all Norwegian residents aged 30 years or older as of January 2009. People with or without T2D at baseline (n=2,992,228) were followed until December 2013. We used Cox regression to estimate adjusted hazard ratios (aHRs).

Results

Pandemic influenza hospitalization was more common in individuals with T2D (aHR=2.46, 95%CI 2.04–2.98). The mortality hazard ratio associated with hospitalization for pandemic influenza was lower in people with T2D (aHR=1.82, 95%CI 1.21–2.74) than in those without T2D (aHR=3.89, 95%CI 3.27–4.62). The same pattern was observed when restricting to 90 days mortality (aHR=3.89, 95%CI 1.25–12.06 among those with T2D and aHR=10.79, 95%CI 7.23–16.10 among those without T2D). The rate of hospitalization for pandemic influenza was 78% lower in those vaccinated compared to non‐vaccinated among people with T2D (aHR=0.22, 95% CI 0.11–0.39), while the corresponding estimate for those without T2D was 59% lower (aHR=0.41, 95%CI 0.33–0.52). Mortality was 25% lower in those vaccinated compared to non‐vaccinated among people with T2D (aHR=0.75, 95% CI 0.73–0.77), while the corresponding estimate for those without T2D was 9% (aHR=0.91, 95%CI 0.90–0.92).

Conclusions

There may have been a lower threshold for pandemic influenza hospitalization for people with T2D, rather than more severe influenza infection. Our combined results support the importance of influenza vaccination among people with T2D, especially during pandemics.