BMJ Open. 2026 Jun 22;16(6):e106480. doi: 10.1136/bmjopen-2025-106480.
ABSTRACT
OBJECTIVES: To compare influenza-related hospitalisation, mortality and effects of background factors in adults with type 2 diabetes (T2D) and age-matched and sex-matched controls. To explore associations between clinical variables and the risk of severe influenza outcomes.
DESIGN: Register-based nationwide cohort study.
SETTINGS: Data from the National Diabetes Register are cross-linked to the Swedish Population Register, Statistics Sweden and the Swedish Patient Register.
PARTICIPANTS: 371 811 patients with T2D from the Swedish National Diabetes Register and 1 728 856 matched control individuals from the Swedish population followed over the 2013/14-2018/19 influenza seasons.
PRIMARY AND SECONDARY OUTCOMES: Data on hospital admissions, mortality, socioeconomic factors and pre-existing conditions were collected. Risk associations were analysed using Cox proportional hazards models. Within the diabetes group, non-linear associations between common clinical variables and influenza hospitalisation were examined.
RESULTS: 1.6% of those with diabetes and 1.0% of controls were hospitalised for influenza, with influenza-related mortality at 0.12% and 0.08% respectively. Adjusted HR for hospitalisation in T2D was 1.57 (95% CI 1.52 to 1.61) and 1.44 (95% CI 1.29 to 1.61) for mortality. Absolute risk was highest in those with cardiovascular, kidney or respiratory disease. Relative risk was greatest in younger (<65 years) patients with T2D. Higher haemoglobin A1c (HbA1c) and lower estimated glomerular filtration rate (eGFR) were linked to increased hospitalisation risk in persons with T2D.
CONCLUSION: This study confirms that T2D increases the risk of hospitalisation and mortality from seasonal influenza. Support to achieve HbA1c and eGFR targets and following vaccination guidelines is important.
PMID:42331591 | DOI:10.1136/bmjopen-2025-106480