Multimorbidity and frailty are complex syndromes characteristics of aging. We reviewed the literature and provided pooled estimations of any evidence regarding (a) the coexistence of frailty and multimorbidity and (b) their association. We searched PubMed and Web of Science for relevant articles up to September 2017. Pooled estimates were obtained through random effect models and Mantel–Haenszel weighting. Homogeneity (I²), risk of bias, and publication bias were assessed. PROSPERO registration: 57890. A total of 48 studies involving 78,122 participants were selected, and 25 studies were included in one or more meta-analyses. Forty-five studies were cross-sectional and 3 longitudinal, with the majority of them including community-dwelling participants (n = 35). Forty-three studies presented a moderate risk of bias and five a low risk. Most of the articles defined multimorbidity as having two or more diseases and frailty according to the Cardiovascular Health Study criteria. In meta-analyses, the prevalence of multimorbidity in frail individual was 72% (95% confidence interval = 63%–81%; I² = 91.3%), and the prevalence of frailty among multimorbid individuals was 16% (95% confidence interval = 12%–21%; I² = 96.5%). Multimorbidity was associated with frailty in pooled analyses (odds ratio = 2.27; 95% confidence interval = 1.97–2.62; I² = 47.7%). The three longitudinal studies suggest a bidirectional association between multimorbidity and frailty. Frailty and multimorbidity are two related conditions in older adults. Most frail individuals are also multimorbid, but fewer multimorbid ones also present frailty. Our findings are not conclusive regarding the causal association between the two conditions. Further longitudinal and well-designed studies may help to untangle the relationship between frailty and multimorbidity.

This review discusses the interplay between multimorbidity (i.e. co‐occurrence of more than one chronic health condition in an individual) and functional impairment (i.e. limitations in mobility, strength or cognition that may eventually hamper a person's ability to perform everyday tasks). On the one hand, diseases belonging to common patterns of multimorbidity may interact, curtailing compensatory mechanisms and resulting in physical and cognitive decline. On the other hand, physical and cognitive impairment impact the severity and burden of multimorbidity, contributing to the establishment of a vicious circle. The circle may be further exacerbated by people's reduced ability to cope with treatment and care burden and physicians’ fragmented view of health problems, which cause suboptimal use of health services and reduced quality of life and survival. Thus, the synergistic effects of medical diagnoses and functional status in adults, particularly older adults, emerge as central to assessing their health and care needs. Furthermore, common pathways seem to underlie multimorbidity, functional impairment and their interplay. For example, older age, obesity, involuntary weight loss and sedentarism can accelerate damage accumulation in organs and physiological systems by fostering inflammatory status. Inappropriate use or overuse of specific medications and drug–drug and drug–disease interactions also contribute to the bidirectional association between multimorbidity and functional impairment. Additionally, psychosocial factors such as low socioeconomic status and the direct or indirect effects of negative life events, weak social networks and an external locus of control may underlie the complex interactions between multimorbidity, functional decline and negative outcomes. Identifying modifiable risk factors and pathways common to multimorbidity and functional impairment could aid in the design of interventions to delay, prevent or alleviate age‐related health deterioration; this review provides an overview of knowledge gaps and future directions.

Heart failure and dementia are common medical conditions in elderly persons.^1,2 Clinical observations³ report that heart failure and lower left ventricular fraction are related to poorer cognitive function. Population-based studies^4-6 show that chronic heart failure is associated with cognitive impairment and cognitive decline independent of vascular disorders and other potential confounders. Furthermore, we have previously reported^7,8 that low diastolic pressure (ie, <70 mm Hg) and a clinically significant decline in systolic pressure are associated with subsequent development of dementia and Alzheimer disease. Based on these findings, we hypothesize that (1) heart failure might be linked to dementia (because cognitive impairment could reflect a prodromal phase of dementia), and (2) heart failure might influence the relationship between low diastolic pressure and dementia given the association between low blood pressure and both heart failure and cognitive impairment in elderly persons.⁹ In the present study, we sought to examine these 2 hypotheses using 9-year follow-up data on a community cohort of older adults. To our knowledge, no prospective cohort studies have examined the relationship between heart failure and dementia risk.

We explored the role of age, gender, and socioeconomic status in the occurrence of chronic diseases and multimorbidity in 1099 elderly participants in the Kungsholmen Project. Cardiovascular and mental diseases were the most common chronic disorders. Of the participants, 55% had multimorbidity. Advanced age, female gender, and lower education were independently associated with a more than 50% increased risk for multimorbidity. Multimorbidity is the most common clinical picture of the elderly and may be increased by unhealthy behaviors linked to education.