Glycemic Control and Risk of Infections Among People With Type 1 or Type 2 Diabetes in a Large Primary Care Cohort Study.

OBJECTIVE: Diabetes mellitus (DM) increases the risk of infections, but the effect of better control has not been thoroughly investigated.

RESEARCH DESIGN AND METHODS: With the use of English primary care data, average glycated hemoglobin (HbA1c ) during 2008-2009 was estimated for 85,312 patients with DM ages 40-89 years. Infection rates during 2010-2015 compiled from primary care, linked hospital, and mortality records were estimated across 18 infection categories and further summarized as any requiring a prescription or hospitalization or as cause of death. Poisson regression was used to estimate adjusted incidence rate ratios (IRRs) by HbA1c categories across all DM, and type 1 and type 2 DM separately. IRRs also were compared with 153,341 age-sex-practice-matched controls without DM. Attributable fractions (AF%) among patients with DM were estimated for an optimal control scenario (HbA1c 6-7% [42-53 mmol/mol]).

RESULTS: Long-term infection risk rose with increasing HbA1c for most outcomes. Compared with patients without DM, those with DM and optimal control (HbA1c 6-7% [42-53 mmol/mol], IRR 1.41 [95% CI 1.36-1.47]) and poor control (≥11% [97 mmol/mol], 4.70 [4.24-5.21]) had elevated hospitalization risks for infection. In patients with type 1 DM and poor control, this risk was even greater (IRR 8.47 [5.86-12.24]). Comparisons within patients with DM confirmed the risk of hospitalization with poor control (2.70 [2.43-3.00]) after adjustment for duration and other confounders. AF% of poor control were high for serious infections, particularly bone and joint (46%), endocarditis (26%), tuberculosis (24%), sepsis (21%), infection-related hospitalization (17%), and mortality (16%).

CONCLUSIONS: Poor glycemic control is powerfully associated with serious infections and should be a high priority.