Relationship between multimorbidity and health-related quality of life of patients in primary care Martin Fortin 1 , Gina Bravo 2,3 , Catherine Hudon 1 , Lise Lapointe 1 , Jose´ Almirall 1 Marie-France Dubois 2,3 & Alain Vanasse 1 1 Department of Family Medicine, Sherbrooke University, Sherbrooke, Que, Canada (E-mail: martinfortin@ videotron.ca); 2 Department of Community Health Sciences, Sherbrooke University, Sherbrooke, Que, Canada ; 3 Research Center on Aging, Sherbrooke University Geriatric Institute, Sherbrooke, Que, Canada Accepted in revised form 11 June 2005 Abstract Previous studies about the association of multimorbidity and the health-related quality of life (HRQOL) in primary-care patients are limited because of their reliance on simple counts of diseases from a limited list of diseases and their failure to assess the severity of disease. We evaluated the association while taking into account the severity of the medical conditions based on the Cumulative Illness Rating Scale (CIRS) score, and controlling for potential confounders (age, sex, household income, education, self-perception of eco- nomic status, number of people living in the same dwelling, and perceived social support). We randomly selected 238 patients to construct quintiles of increasing multimorbidity (CIRS). Patients completed the 36- item Medical Outcomes study questionnaire (SF-36) to evaluate their HRQOL. Applying bivariate and multivariate linear regression analyses, we used the CIRS as either a continuous or a categorical (quintiles) variable. Use of the CIRS revealed a stronger association of HRQOL with multimorbidity than using a simple count of chronic conditions. Physical more than mental health deteriorated with increasing multi- morbidity. Perceived social support and self-perception of economic status were significantly related to all scales of the SF-36 ( p < 0.05). Increased multimorbidity adversely affected HRQOL in primary-care adult patients, even when confounding variables were controlled for. Key words: Chronic disease, Family medicine, Health-related quality of life, Multimorbidity or comorbidity Abbreviations: BP – Bodily pain; CIRS – Cumulative Illness Rating Scale; GH – General health; HRQOL – Quality of life; HT – Health transition; MCS – Mental component summary; MH – Mental health; PCS – Physical component summary; PF – Physical functioning; RE – Role emotional; RP – Role physical; SF – Social functioning; SF-36 – 36-item Medical Outcomes Study questionnaire; VT – Vitality scale Introduction Of the 90 million Americans living with a chronic medical condition in 1987, 43% had more than one chronic condition, or multimorbidity [1]. Epidemiological data [2–4] from studies done in several countries confirm that patients with multimorbidity comprise an important portion of family doctors’ patients. Estimates of its preva- lence vary from 17% for patients aged between 20 and 39 years [3] to 98% for patients aged 65 years and older [4]. However, outcomes asso- ciated with multimorbidity have not been studied in depth. The health-related quality of life (HRQOL), a subjective outcome measure that has been used to Quality of Life Research (2006) 15: 83–91 Ó Springer 2006 DOI 10.1007/s11136-005-8661-z