BACKGROUND: Little is known about how multimorbidity, dementia and increasing age combine to influence health outcomes or utilization. Our objective was to examine the joint associations between age, dementia and burden of morbidity with mortality and other clinical outcomes.
METHODS: We did a retrospective population-based cohort study of all adults aged 65 years and older residing in Alberta, Canada, between 2002 and 2013. We used validated algorithms applied to administrative and laboratory data from the provincial health ministry to assess the presence/absence of dementia and 29 other morbidities, and their associations with mortality (our primary outcome), other clinical outcomes (emergency department visits, all-cause hospital admissions) and a proxy for loss of independent living (discharge to long-term care). Cox and Poisson models were adjusted for year-varying covariates. A 3-way interaction was modelled for dementia, the number of comorbidities, and age.
RESULTS: There were 610 457 adults aged 65 years and older living in Alberta over the study period. Over median follow-up of 6.8 years, 153 125 (25.1%) participants died and 5569 (0.9%) were discharged to long-term care. The prevalence of people with at least 3 morbidities was 33.7% in 2003 and 50.2% in 2012. The prevalence of dementia rose from 6.2% in fiscal year 2003 to 8.3% in fiscal year 2012, representing a net increase of approximately 13 700 people. The likelihood of all 4 outcomes increased with age and with greater burden of morbidity; the presence of dementia further increased these risks. For example, the risk of mortality increased by 1.54 to 6.38 in the presence of dementia, depending on age and morbidity burden. The risk associated with dementia was attenuated by increasing comorbidity.
INTERPRETATION: Older age, multimorbidity and dementia are all strongly correlated with adverse health outcomes as well as a proxy for loss of independent living. The increasing prevalences of dementia and multimorbidity over time suggest the need for coordinated national strategies aimed at mitigating the health challenges associated with the aging of the population.
- Older adults