Neuropathological diagnoses and age-related differences in Finnish medico-legal autopsies of individuals aged 65 years and older.

As populations worldwide continue to grow older, an increase in cases involving aged individuals is also to be expected in medico-legal autopsies. The aim of this study was to report the neuropathological diagnoses of individuals aged ≥ 65 years, and to compare the findings across three age groups: youngest-olds (65-74 years of age), middle-olds (75-84) and oldest-olds (≥ 85). The sample comprised all Finnish medico-legal autopsies of individuals aged ≥ 65 years whose autopsy included a full neuropathological examination performed by a neuropathologist over the period 2016-2022 (n = 629). Neuropathological diagnoses were obtained from the neuropathologists' reports, and background characteristics were collected from medico-legal cause-of-death investigation documents. Of all cases, 97.1% received at least one neuropathological diagnosis. The prevalences of many neurodegenerative diseases increased with age; Alzheimer's disease neuropathological change (30.5%) and cerebral amyloid angiopathy (14.0%) were the most common ones. However, some rarer neurodegenerative diseases were more frequent among youngest-olds. While the prevalence of acute infarcts remained relatively consistent across the age groups (12.4-14.5%), old infarcts and subarachnoid haemorrhages were most common among oldest-olds (22.1% and 16.6%, respectively). The age-related increase in subarachnoid haemorrhage diagnoses appeared to be primarily driven by the male sex. The prevalences of acute and old traumatic brain injuries were rather low (5.7-6.2% and 5.1%, respectively) and remained relatively stable across the age groups. In conclusion, our data suggest that neuropathological diagnoses are highly prevalent among aged individuals undergoing medico-legal autopsy, and many diagnoses become more frequent towards oldest-olds.