Criminal Trajectories Across the Dementia Timeline-A Nationwide Finnish Register Study

The aim of this longitudinal register study was to examine the crime counts, crime incidence and timing of criminal activity in relation to the diagnosis of Alzheimer's disease (AD), frontotemporal dementia (FTD) and Lewy body dementias (LBD). The objective was to analyse the associated risk factors and risk relations among the offender categories.

We collected register data from Finnish nationwide registers (Finnish Care Register for Health Care and Finnish National Police Register) between 1998 and 2015. Mortality statistics were collected until the end of 2018 (Statistics Finland). Our study included a total of 92,189 patients, of whom 80,540 had AD, 1059 had FTD, and 10,590 had LBD. We examined the crimes committed by the study population before and after diagnosis. In the follow-up, we primarily focussed on the 4-year period and secondarily on the 10-year period after diagnosis. First, we measured the post-diagnostic crime rates in patients who had committed crimes before diagnosis and in those who had not; we also calculated the incidence rate ratio (IRR) of post-diagnosis crimes in these groups. Second, we calculated the cumulative incidence of first post-diagnoses crimes and investigated the risk of the first post-diagnoses crime by calculating the adjusted subhazard ratio (sHR) in pre-diagnosis offenders and non-offenders.

Most of the study population did not exhibit criminal behaviour before or after diagnosis. However, individuals who had engaged in criminal behaviour before diagnosis also showed a higher incidence of criminal activity in the 4-year period after diagnosis compared to patients with no criminal history prior to diagnosis. They also showed a steep increase in the cumulative incidence of the first post-diagnosis crime, particularly in the first 2 years after diagnosis. The age- and sex-adjusted sHR for the occurrence of the first post-diagnosis crime was 4.42 (95% confidence interval: 3.83-5.11) in AD, 4.36 (2.15-8.83) in FTD and 4.87 (3.88-6.12) in LBD in pre-diagnosis offenders versus non-offenders.

Individuals with a history of criminal behaviour before diagnosis of a neurocognitive disorder showed higher rates and a higher risk of future criminal activity. The cumulative incidence rose steeply during the first 2 years after diagnosis and after more gradually. Criminal activity closer to the time of diagnosis, especially 1 year prior, was the strongest predictor in increasing the risk of future criminal behaviour.