The Journals of Gerontology: Series B

Objectives Very early-life conditions are recognised as critical for healthy brain development. This study assesses early life risk factors for developing dementia. In absence of historical medical birth records, we leverage an alternative full population approach using demographic characteristics obtained from administrative data to derive proxy indicators for birth complications and unfavourable birth outcomes. We utilise proxy variables to investigate the impact of early-life risk factors on dementia risk. Methods We use administrative individual-level data for full cohorts born 1932–1950 in Sweden with multi-generational linkages. Records on hospitalisation and mortality are used to identify dementia cases. We derive three birth risk factors based on demographic characteristics: advanced maternal age, narrow sibling spacing, and twin births, and apply survival analysis to evaluate long-term effects on dementia risk. We control for confounding using multiple SES indicators, including parental surnames, and by implementing a sibling design. As comparison exposure we add low education from 1970 Census. Results The presence of at least one birth risk factor increases dementia risk (HR = 1.059.; 95% CI: [1.034,1.085]). The occurrence of twin birth poses a particularly heightened risk. (HR=1.166; 95% CI: [1.084,1.255]). Discussion Improvements to the very early life environment hold significant potential to mitigate dementia risk. A comparison to the influence of low education on dementia (largest known modifiable risk factor) suggests that demographic birth characteristics are of relevant effect sizes. Our findings underscore the relevance of providing assistance for births experiencing complications and adverse health outcomes to reduce dementia cases.