Arthritis Care & Research Vol. 69, No. 1, January 2017, pp 12–20 DOI 10.1002/acr.22996 V C 2016, American College of Rheumatology SPECIAL THEME ARTICLE: COMORBIDITIES AND THE RHEUMATIC DISEASES Patterns and Consequences of Multimorbidity in the General Population: There is No Chronic Disease Management Without Rheumatic Disease Management DANIELA SIM ~ OES, 1 F  ABIO A. ARA  UJO, 2 MILTON SEVERO, 2 TERESA MONJARDINO, 2 IVO CRUZ, 3 LORETO CARMONA, 4 AND RAQUEL LUCAS 2 Objective. To identify empirical model-based patterns of multimorbidity from chronic noncommunicable diseases in the general population, with a focus on the contribution of rheumatic and musculoskeletal diseases (RMDs), and to quantify their association with adverse health outcomes. Methods. Cross-sectional data from the Portuguese Fourth National Health Survey were analyzed (n 5 23,754). Latent class analysis was used to identify patterns of coexistence of 11 chronic noncommunicable diseases (RMDs, diabetes mellitus, hypertension, chronic obstructive pulmonary disease, stroke, depression, myocardial infarction, cancer, osteoporosis, asthma, and renal failure). Based on the Outcome Measures in Rheumatology, filter 2.0, health outcomes included life impact, pathophysiologic manifestations, and resource use. We assessed the association between patterns and adverse health out- comes, through sex-, age-, and body mass index–adjusted prevalence ratios with 95% confidence intervals, obtained using Poisson regression. Results. Four patterns of chronic noncommunicable diseases co-occurrence were identified and labeled as low disease prob- ability, cardiometabolic conditions, respiratory conditions, and RMDs and depression. RMDs were highly prevalent in patients with chronic diseases (from 38.6% in cardiometabolic conditions to 66.7% in RMDs and depression). While negative self-rated health, short-term disability, and chronic pain were more strongly associated with cardiometabolic conditions and respiratory conditions, all multimorbidity patterns were similarly associated with long-term disability, frequent health care utilization, and out-of-pocket health care expenses. Conclusion. Our study emphasizes RMDs as a major presence in multimorbidity in the general population. All multi- morbidity patterns were associated with a wide set of adverse health outcomes. Management strategies for the patient with chronic cardiometabolic, respiratory, or depressive conditions should also target RMDs. INTRODUCTION A substantial part of the adult population experiences the con- current presence of more than 1 chronic disease, which is a phenomenon known as multimorbidity (1). At the patient level, multimorbidity is associated with higher mortality (2), worsened functional status, and poorer quality of life (3). At the health care level it implies postoperative complications (4), longer hospital stays, higher likelihood of readmission (5), more frequent health care utilization, and higher direct costs (6). Chronic noncommunicable diseases (NCDs) frequently aggregate due to shared pathophysiologic mechanisms, either as sequential steps in the same causal pathway or as common results of the same exposures. Additionally, at the population level, diseases may also aggregate due to chance alone, i.e., the more prevalent a disease is the more likely it is to coexist with others, even in the absence of a direct causal relation. EPIUnit research unit is supported by the National Founda- tion for Science and Technology (FCT UID/DTP/04750/2013/ 002). Drs. Ara ujo, Monjardino, and Lucas’s work was supported by the FCT (grants 85398/2012, 92370/2013, and 88729/2012, respectively). 1 Daniela Sim~ oes, MSc: University of Porto, Porto, Portugal, and Cooperativa de Ensino Superior Polit ecnico e Univer- sit ario, Gandra, Paredes, Portugal; 2 F abio A. Ara ujo, MSc, Milton Severo, PhD, Teresa Monjardino, MSc, Raquel Lucas, PhD: University of Porto, Porto, Portugal; 3 Ivo Cruz, MD, MSc: University of Porto, and ACeS Grande Porto V, Porto Ocidental, Porto, Portugal; 4 Loreto Carmona, MD, PhD: Instituto de Salud Musculoesqueletica, Madrid, Spain. Address correspondence to Raquel Lucas, PhD, EPIUnit, Instituto de Sa ude P ublica da Universidade do Porto, Rua das Taipas, 135-139, 4050-600 Porto, Portugal. E-mail: rlucas@ med.up.pt. Submitted for publication February 29, 2016; accepted in revised form July 19, 2016. 12