Impact of cardiovascular and neuropsychiatric multimorbidity on older adults' health

Abstract

Multimorbidity, the presence of two or more chronic diseases in one person, is common in older people, and associates with a number of negative outcomes. In this thesis, we propose a methodology to assess and measure multimorbidity in older individuals. We use it to describe the longitudinal evolution and prognosis of multimorbidity clusters, and to investigate the extent to which clusters of cardiovascular and neuropsychiatric multimorbidity impact and interact with physical function. Data are from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), a population-based study including 3,363 community-dwelling and institutionalized individuals aged ≥60 years.

Study I. We provided a clinically driven list of 60 chronic diseases for the assessment of multimorbidity in older adults. After applying this methodology to the 3,363 SNAC-K participants, we found that 88.6% of them had two or more diseases, 73.2% had three or more diseases, and only 11.4% had zero or one single disease. Given the ceiling effect associated with the use of a cutoff, multimorbidity should be rather be considered as a continuous metric, which better reflects the progressive accumulation of diseases starting in early aging and continuing up to very late life. Study II. We identified and traced the evolution of multimorbidity clusters over 12 years of 2,931 SNAC-K participants with two or more diseases. At baseline, 51.3% of participants were included in one of five clusters; the rest were part of an unspecified group, given that no disease patterns could cluster them. Cardiometabolic risk factors, the evolution of several diseases, and death may have steered most of the longitudinal transitions among the multimorbidity clusters we described over a period of 12 years. Study III. We investigated the association of cardiovascular and neuropsychiatric multimorbidity with 9 years of change in walking speed and intact basic activities of daily living in 2,385 SNAC-K participants. Neuropsychiatric disease, alone or combined with cardiovascular disease, showed the strongest detrimental impact on functional decline. Cardiovascular multimorbidity showed an association solely with decline in walking speed. Study IV. We studied the interplay between cardiovascular multimorbidity and functional impairment, as well as between neuropsychiatric multimorbidity and functional impairment, on all-cause and causespecific mortality in 3,241 SNAC-K participants. Slow walking speed provided additional prognostic information in terms of all-cause and cause-specific mortality beyond the number of both cardiovascular and/or neuropsychiatric diseases.

Conclusions. The use of a standardized methodology to assess chronic disease and multimorbidity may enhance comparability across studies, settings, and geographical regions. Studying the natural evolution of multimorbidity in older individuals may help to better hypothesize about underlying mechanisms and provide important prognostic information. In this regard, multimorbidity clusters including cardiovascular and neuropsychiatric disease emerge as major determinants of functional decline and higher mortality rate. Finally, the adoption of a simple and easy-to-use measure of functional impairment such as walking speed may help health-care professionals identify older people affected by specific groups of chronic disease with similar needs, health trajectories, and prognoses.