Subjective memory impairment, instrumental activities of daily living and longitudinal effect on mortality among older adults in a population-based cohort study: The HUNT Study

Background: Subjective impairment in memory and instrumental activities in daily living (IADL) are associated with future cognitive decline and poorer mental health in older adults, but their association with mortality is uncertain. Our aim was to examine the associations between subjective memory and IADL impairments and all-cause mortality, as well as the mortality risk for reporting both memory and IADL impairments. Methods: Data from the 70-year-old and older cohort in the third survey of a population-based study, the Nord-Trøndelag Health Study (HUNT3), were linked to the Norwegian Causes of Death Registry. A total of 5802 older adults had complete data from HUNT3 (70.8% of the 70+ cohort). The mean follow-up time was 8.0 years, and 1870 respondents had died. Associations between subjective memory and ADL impairments with mortality were analysed in Cox regression models adjusted for covariates with attained age as the timescale. Analyses were performed separately for two age groups – 70–79 and 80+ years – to fulfil the proportional hazards assumption. Results: Subjective impairments in short-term memory and IADL were significantly associated with mortality both separately and combined. These associations were strongest in the 70- to 79-year-old group, where reporting impairment on one short-term memory item increased the mortality risk by 51% (hazard ratio=1.51; 95% confidence interval 1.20–1.91). Long-term memory impairments were not associated with mortality in the adjusted models. Conclusions: Subjective short-term memory impairments and IADL impairments are associated with increased mortality risk. Neither of these symptoms should be regarded as benign aspects of ageing, and concerns should be properly addressed