Are sleep and stress linked to the size of specific parts of the hippocampus?

Details

The study examined cross-sectional and 2-year follow-up relationships between sleep and stress and both total hippocampal volume and hippocampal subfield volumes in older adults. It included 417 adults from the Irish Longitudinal Study on Ageing, aged 68.8 ± 7.3 years, 54% of whom were women; they completed an interview, a questionnaire, and multiparametric brain magnetic resonance imaging.

The researchers used ordinary least squares regressions to examine relationships between self-reported sleep duration, sleep problems, perceived stress, and total hippocampal volume. They used linear mixed-effects models to investigate relationships between hippocampal subfield volumes and sleep duration, sleep problems, perceived stress, and changes in these measures over 2 years.

Neither sleep nor stress was associated with total hippocampal volume in the cross-sectional or follow-up analyses. In contrast, long sleep (≥9–10 hours per night) was associated with smaller volumes of the molecular layer, hippocampal tail, presubiculum, and subiculum. Short sleep (≤6 hours) occurring alongside perceived stress was associated with smaller volumes of cornu ammonis 1, the molecular layer, subiculum, and tail. Sleep problems independently and together with higher stress, as well as an increase in sleep problems over 2 years, were associated with smaller volumes of these same subfields.

The authors concluded that assessing suboptimal sleep and stress together is important for phenotyping individuals at risk of hippocampal subfield atrophy.