National registry-based case-control study: comorbidity and stroke in young adults

Stroke is overrepresented in cohorts of young adults with chronic diseases. The prevalence and impact of comorbidity among young stroke patients have not been compared with individuals without stroke. Our aim was to investigate the association between comorbidity and stroke in young adults.

A nationwide cohort of patients (aged 15-44 years), registered in the Swedish Stroke Register, (Riksstroke) 2001-2009, was identified. Age- and sex-matched controls were randomly selected from the Population Register of Sweden. Discharge diagnoses were retrieved from the National Patient Register and grouped by chapter in the International Classification of Diseases 10th revision. Associations between ICD-10 chapters and stroke were stratified (age, sex, and stroke type) and analyzed by multivariable logistic regression.

In 2599 stroke patients analyzed, the prevalence of vascular risk factors (hypertension 25.3%, dyslipidemia 13.0%, diabetes 9.7%, heart failure 3.2%, and atrial fibrillation 2.8%), all ICD-10 chapters (except pregnancy) and prestroke hospitalizations were more frequent among cases than controls. Independent associations were found between stroke and eight ICD-10 chapters: neoplasms (odds ratios (OR) 1.53, 95% CI 1.15-2.05), blood (OR 1.61, 1.11-2.34), endocrine (OR 2.28, 1.77-2.93), psychiatric (OR 1.50, 1.24-1.81), nervous (OR 1.91, 1.46-2.50), eye (OR 1.67, 1.05-2.64), circulatory (OR 3.05, 2.45-3.80), and symptoms (OR 1.31, 1.13-1.52). The risk of stroke increased by 26% per ICD-10 chapter diagnosed.

In addition to vascular risk factors, comorbidity (represented by ICD-10 chapters) was associated with increased risk of stroke in young individuals. The risk of stroke was further increased with the number of diagnosed ICD-10 chapters.