Risk of dementia and mild cognitive impairment in older adults with a criminal background: a population-based register study in Sweden.

Criminal behaviour has previously been associated with an increased risk for several mental health problems, but little is known about the association between criminal behaviour and dementia. We aimed to examine how the criminal background (type of crime, number of convictions, length of the sentence) is associated with dementia and mild cognitive impairment (MCI), and how mental and physical health disorders and educational attainment influenced these associations. A nationwide cohort of 3,617,028 individuals born between 1932 and 1962 were linked with criminal and medical records using Swedish national registers. We used Cox regression models to examine the associations. Increased risks for dementia (Hazard ratios (HRs) 1.54, 95% confidence interval (CI) 1.50-1.57) and MCI (1.55, 1.50-1.61) were found in individuals with criminal background, particularly among those who committed violent or several crimes, or with long sentences. After full adjustment of covariates, the associations attenuated but remained statistically significant for dementia (1.25, 1.22-1.28) and MCI (1.27, 1.22-1.32). The attenuation was mostly explained by mental health problems -depression, anxiety, schizophrenia spectrum disorders, substance use disorder (SUD), and bipolar disorder- (dementia: 1.34, 1.31-1.37; MCI: 1.35, 1.30-1.40). SUD contributed the most to attenuate the associations. Our results may provide important insights to health and penal systems by showing the importance of considering the severity of the criminal background and life-course mental health when assessing the risk of neurodegenerative disorders.