Psychological distress in later life and incident dementia: The Ohsaki Cohort 2006 Study

Abstract

BackgroundThe role of reverse causation in the association between psychological distress and incident dementia remains unclear. We investigated whether psychological distress is a risk factor for, or prodromal symptom of, dementia. MethodsA longitudinal analysis of psychological distress with incident dementia was conducted among 12,076 Japanese individuals (age ≥65 years) followed for 5.7 years. Psychological distress was measured using the Kessler 6-item psychological distress scale (0–24 points) at baseline, with participants categorized into four psychological distress groups: no (0–4), mild (5–9), moderate (10–12), and serious (13–24). Dementia cases were retrieved from the public Long-term Care Insurance database. Cox proportional hazards model was used to estimate the multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (95%CIs) for incident dementia. Stratified analysis was conducted by cognitive function (higher or lower) at baseline. ResultsDuring 60,240 person-years of follow-up, 997 individuals developed dementia. A dose-response association was found between psychological distress and dementia; however, the stratified analysis indicated that this association depended on cognitive function at baseline. Among those with higher cognitive function at baseline, a significantly elevated dementia risk was observed only for serious psychological distress (HR: 2.04, 95%CI: 1.24–3.36). Among those with lower cognitive function, both moderate (HR: 1.30, 95%CI: 1.00–1.68) and serious (HR: 1.79, 95%CI: 1.37–2.34) psychological distress showed an increased dementia risk. ConclusionThe association between late-life psychological distress and incident dementia is partly explained by reserve causation, whereby mild and moderate distress could be a prodromal symptom of dementia.