Objective: Despite the high prevalence of late-life depression and anxiety at threshold and subthreshold levels, their joint role in the disablement process remains unclear. This study aims to examine the association of comorbid occurring depression and anxiety across the full spectrum of symptom severity with disability onset in older adults.
Methods: The study included 3663 participants from the 2011 National Health and Aging Trends Study who reported no limitations in self-care and mobility activities at baseline. Disability onset was defined as a report of receiving help from another person in any of the activities for three consecutive months. Depression and anxiety symptoms were measured using the 4-item Patient Health Questionnaire, grouped into low, mild and moderate/severe symptom groups. Cox proportional hazards models were used to estimate relative risks for disability onset over a five-year period by depression/anxiety symptom groups.
Results: A total of 1047 participants developed disability (24.6%; 6.0 per 1000 person-months). At baseline, one-fifth of the sample reported mild (n=579, 16%; 31.6% with disability onset) or moderate/severe symptoms (n=156, 4%; 38.1% with disability onset). After adjustment for socio-demographics, there was a dose-response relationship between depression/anxiety symptom groups and disability onset (mild vs low: Hazard Ratio [HR]=1.43, 95% Confidence Interval[CI]=1.20-1.70; moderate/severe vs low: HR=1.94, 95% CI=1.45-2.59). The increased risk remained significant after adjustment for health status variables for the mild symptom group (HR=1.26, 95% CI=1.07-1.49), but not for the moderate/severe symptom group (HR=1.30, 95% CI=0.94-1.79), possibly reflecting lower statistical power.
Conclusions: Findings suggest that the full spectrum of depression and anxiety symptoms are associated with increased risk for disability in late life. Their role in the disablement process warrants further investigation.