Estimating multiple morbidity disease burden among older persons: a convergent construct validity study to discriminate among six chronic illness measures, CCHS 2008/09

Wister et al. BMC Geriatrics (2015) 15:12 DOI 10.1186/s12877-015-0001-8 RESEARCH ARTICLE Open Access Estimating multiple morbidity disease burden among older persons: a convergent construct validity study to discriminate among six chronic illness measures, CCHS 2008/09 Andrew V Wister1*, Mélanie Levasseur2,3, Lauren E Griffith4,5 and Ian Fyffe1 Abstract Background: Since approximately two in three older adults (65+) report having two or more chronic diseases, causes and consequences of multimorbidity among older persons has important personal and societal issues. Indeed, having more than one chronic condition might involve synergetic effects, which can increase impact on disabilities and quality of life of older adults. Moreover, persons with multimorbidity require more health care treatments, implying burden for the person, her/his family and the health care system. Methods: Using the 2008/09 Canadian Community Health Survey (CCHS), this paper assesses the convergent construct validity of six measures of multimorbidity for persons aged 65 and over. These measures include: 1) Multimorbidity Dichotomized (0, 1+ conditions); 2) Multimorbidity Dichotomized (0/1, 2+); 3) Multimorbidity Additive Scale; 4) Multimorbidity Weighted by the Health Utility (HUI3) Scale; 5) Multimorbidity Weighted by the OARS Activity of Daily Living (ADL) Scale; and 6) Multimorbidity Weighted by HUI3 (using beta coefficients). Convergent construct validity was assessed using correlations and OLS regression coefficients for each of the multimorbidity measures with the following social-psychological and health outcome variables: life satisfaction, perceived health, number of health professional visits, and medication use. Results: Overall, the two dichotomies (scales #1 & #2) showed the weakest construct validity with the health outcome variables. The additive chronic illness scale (#3) and the multimorbidity weighted by ADLs (#5), performed better than the other two weighted scales using (HUI #4 & #6). Measurement errors apparent in the dichotomous multimorbidity measures were amplified for older women, especially for life satisfaction and perceived health, but decreased when using the scales, suggesting stronger validity of scales #3 through #6. Conclusions: To properly represent multimorbidity, using dichotomous measures should be used with caution. When only prevalence data are available for chronic conditions, such as in the CCHSs or CLSA, an additive multimorbidity scale can better measure total illness burden than simple dichotomous or other discrete measures. Keywords: Multimorbidity indices, Surveys, Validation, Older adults * Correspondence: 1 Department of Gerontology, Simon Fraser University, 2800-515 Hastings Street, Vancouver, BC V6B 5K3, Canada Full list of author information is available at the end of the article © 2015 Wister et al.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Wister et al. BMC Geriatrics (2015) 15:12 Background The study of the causes and consequences of multimorbidity has become highly important in recent years, especially among older persons given rapid population aging. Several interlocking trends explain such interest: approximately two in three seniors report having two or more chronic conditions, persons with multimorbidity require more health care treatments, and having more than one chronic illness may have synergetic detrimental (negative) effects [1-3]. Multimorbidity, the focus of the present study, is defined as conditions where an individual has been diagnosed with more than one chronic disease – a condition that is slow in progression, long in duration, and typically limits function, productivity and quality of life [4,5]. This can be distinguished from comorbidity, which also includes multiple chronic illnesses, but is defined in terms of an index disease, such as persons with cardiovascular disease who also have diabetes [6]. Although multimorbidity and comorbidity are overlapping terms, comorbidity tends to be used in research that focuses on one particular disease and a set of ‘secondary’ conditions, whereas multimorbidity simply includes all conditions that are present [4-6]. Although research within particular disease pillars (e.g., cardiovascular disease, cancer, arthritis, diabetes, etc.) has proliferated, a gap exists in the literature that addresses the simultaneous experience of living with multimorbidity. Investigation into the etiology, trajectories, and outcomes of experiencing multimorbidity can help to understand total chronic illness burden and its risk factors [6,7]. Such understanding is important for several reasons, particularly, disentangling confounding (mediating or moderating) effects, and addressing the limitations of small numbers of cases for many illnesses found in secondary data sets, which reduces statistical efficiency [7,8]. In addition, and especially for older adults due to the trajectory of illness patterns across the age span, there may exist multiplicative or synergetic effects with the presence of multimorbidity that may be masked when grouping conditions together without taking into account specific numbers and differential impact of conditions. Whereas clinical studies of multimorbidity (or comorbidity) typically require detailed diagnostic data often from medical health records, such as type, onset and severity of illness, many population health surveys are restricted to selfreported prevalence data, thereby limiting public health research to simple measurement methods [9,10]. Given the availability of a growing number of national population health surveys internationally and in Canada, such as the Canadian Community Health Survey (CCHS) and the Canadian Longitudinal Study on Aging (CLSA), there is a need for better understanding of measurement approaches that tap into the complex public health issues of multimorbidity, including its causes and consequences. Page 2 of 12 This paper seeks to fill this gap in knowledge by examining the convergent construct validity of six measures of multimorbidity for persons aged 65 and over using the 2008/09 CCHS - Healthy Aging survey. While comorbidity and multi-morbidity are defined differently, there are common methodological approaches such that developments in one area can be applied to the other [7-9] In a systematic review, available methods to measure comorbidity published between 1966 and 2000 were compared and assessed with respect to their validity and reliability [7]. The majority used a list of defined diagnoses, disab (...truncated)