Multimorbidity and mortality in older adults: A systematic review and meta-analysis

To review literature and provide a pooled effect for the association between multimorbidity and mortality in older adults. A systematic review was performed of articles held on the PUBMED database published up until January 2015. Studies which used different diseases and other conditions to define frailty, evaluated multimorbidity related only to mental health or which presented disease homogeneity were not included. A meta-analysis using random effect to obtain a pooled effect of multimorbidity on mortality in older adults was conducted only with studies which reported hazard ratio (HR). Stratified analysis and univariate meta-regression were performed to evaluate sources of heterogeneity. Out of 5806 identified articles, 26 were included in meta-analysis. Overall, positive association between multimorbidity and mortality [HR: 1.44 (95%CI: 1.34; 1.55)] was detected. The number of morbidities was positively related to risk of death [HR: 1.20 (95%CI: 1.10; 1.30)]. Compared to individuals without multimorbidity, the risk of death was 1.73 (95%CI: 1.41; 2.13) and 2.72 (95%CI: 1.81; 4.08) for people with 2 or more and 3 or more morbidities, respectively. Heterogeneity between studies was high (96.5%). The sample, adjustment and follow-up modified the associations. Only nine estimates performed adjustment which included demographic, socioeconomic and behaviour variables. Disabilities appear to mediate the effect of multimorbidity on mortality. Multimorbidity was associated with an increase in risk of death. Multimorbidity measurement standardization is needed to produce more comparable estimates. Adjusted analysis which includes potential confounders might contribute to better understanding of causal relationships between multimorbidity and mortality.