Development and validation of a multi-domain multimorbidity resilience index for an older population: results from the baseline Canadian Longitudinal Study on Aging

Background: Multimorbidity is recognized as a major public health issue that increases with age and affects approximately two-thirds of older people in Canada, the US, Australia and many European countries. This study develops and tests a three domain (functional, social and psychological) multimorbidity resilience composite index based on a previously developed lifecourse model of multimorbidity resilience, incorporating measures of adversity and positive adaptation. The criterion validity of the measure is demonstrated by means of an analysis of key outcome variables drawn from the literature. Methods: We used the baseline data from the Comprehensive Cohort of the Canadian Longitudinal Study on Aging. Associations of functional, social, psychological as well as total resilience with two health utilization and three illness context outcome variables were examined using logistic regression analyses, adjusted for age, gender, marital status, income, education, region, and number of chronic conditions. Results: The sample included all 6771 Canadian adults aged 65 or older (mean age 73.0, 57% women) who reported two or more of 27 possible chronic conditions. Total resilience was associated with: perceived health (OR = 1.68, CI 1.59-1.77); sleep quality (OR = 1.34, CI 1.30-1.38); perceived pain (OR = 0.80, CI 0.77-0.83); hospital overnight stays (OR = 0.87, CI 0.83-0.91); and emergency department visits (OR = 0.90, CI 0.87-0.94)., after adjusting for socio-demographic factors, and number of chronic conditions. These associations were similar for the unadjusted models, as well as for the functional, social and psychological resilience sub-indices. Conclusions: Combining components of adversity and positive adaptation within functional, social and psychological domains produces a measure of multimorbidity resilience that is associated with more positive health outcomes. Several implications of a composite multimorbidity resilience measure for clinical practice are identified. This measure can be replicated using measures found in other secondary health data sets. Future validation using longitudinal data is warranted.