Abstract
IMPORTANCE: Elite-level contact sport participation is associated with increased dementia risk, which may be attributable to sport-related traumatic brain injury and repetitive head impact exposure. However, the contribution of wider, potentially modifiable dementia risk factors remains uncertain. OBJECTIVE: To explore the association of potentially modifiable dementia risk factors with dementia risk among former professional soccer players. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study used electronic health record linkage to national electronic datasets of general and mental health hospital inpatient and day-case admissions, prescribing information, and death certification in Scotland for male former professional soccer players born between January 1, 1900, and December 31, 1990, who were aged 30 years or older on December 31, 2020, and general population control individuals matched by sex, year of birth, and area socioeconomic status. Database interrogation was performed on November 30, 2021, and data were analyzed between January 16, 2023, and July 8, 2024. EXPOSURES: History of smoking, depression, alcohol-related disorders, diabetes, hypertension, hearing loss, and obesity coded within electronic health records. MAIN OUTCOMES AND MEASURES: Prevalence of dementia risk factors and their association with incident dementia diagnoses were evaluated and compared between former soccer players and matched controls. RESULTS: The final cohort consisted of 11 984 male former professional soccer players and 35 952 matched controls. Over a median 21 years (IQR, 7-34 years) of follow-up from study entry at age 30 years or older, providing a total of 1 039 848 years of follow-up, 434 former soccer players (3.62%) and 453 matched population controls (1.26%) were identified with a dementia diagnosis (hazard ratio [HR], 3.02; 95% CI, 2.54-3.58; P < .001). Overall, rates of general health and lifestyle dementia risk factors were similar or lower among former soccer players compared with matched controls (eg, diabetes: 4.26% vs 6.35%). Dementia risk associated with these factors among soccer players was similar to or lower than among controls (eg, hypertension: HR, 4.62 [95% CI, 3.69-5.78] vs 6.96 [95% CI, 5.64-8.59]). CONCLUSIONS AND RELEVANCE: This cohort study found no evidence that high dementia risk among former professional soccer players was associated with potentially modifiable general health and lifestyle dementia risk factors. These data support continuation of measures directed toward reducing exposure to repetitive head impacts and traumatic brain injury in sport.