Multimorbidity

Abstract

Multimorbidity (two or more coexisting conditions in an individual) is a growing global challenge with substantial effects on individuals, carers and society. Multimorbidity occurs a decade earlier in socioeconomically deprived communities and is associated with premature death, poorer function and quality of life and increased health-care utilization. Mechanisms underlying the development of multimorbidity are complex, interrelated and multilevel, but are related to ageing and underlying biological mechanisms and broader determinants of health such as socioeconomic deprivation. Little is known about prevention of multimorbidity, but focusing on psychosocial and behavioural factors, particularly population level interventions and structural changes, is likely to be beneficial. Most clinical practice guidelines and health-care training and delivery focus on single diseases, leading to care that is sometimes inadequate and potentially harmful. Multimorbidity requires person-centred care, prioritizing what matters most to the individual and the individual's carers, ensuring care that is effectively coordinated and minimally disruptive, and aligns with the patient's values. Interventions are likely to be complex and multifaceted. Although an increasing number of studies have examined multimorbidity interventions, there is still limited evidence to support any approach. Greater investment in multimorbidity research and training along with reconfiguration of health care supporting the management of multimorbidity is urgently needed.

Figure 1. Prevalence of multimorbidity.

Figures 1a and b show prevalence estimates of multimorbidity according to age in high-income countries (HICs; a; data from ^,–) and low-income and middle-income countries (LMICs; b; data from ^,,–). In general, it can be readily observed that the prevalence of multimorbidity increases with age, although estimates vary among studies. Apart from differences in geographic settings, differences among studies may arise from the recruitment method and sample size, data collection, and the operational definition of multimorbidity used, which includes the number of diagnoses considered (e.g. 2 or more, 3 or more), and the conditions considered in the list. The most appropriate estimates for a given population are probably those obtained from a large sample and using the most prevalent long-term conditions with a high impact or burden in that population. When comparing prevalence estimates of multimorbidity between HICs and LMICs, lower age specific rates are observed in LMICs. To our knowledge, the reason of this difference has not been addressed in prevalence studies, and the question whether the difference is due to factors such as ascertainment of conditions (e.g. fewer conditions diagnosed), effects linked to survival (e.g. shorter survival after acute events), or if it is a true difference, remains to be answered. Figure 1c shows the difference in prevalence of multimorbidity (defined as two or more of 40 conditions) by age, between the most and least affluent tenths of the population. Multimorbidity prevalence increases steeply with age in all groups, and (apart from in the very oldest) is consistently higher in the less affluent with the largest difference between groups in middle age.

Figure 2. Determinants of Multimorbidity.

The figure summarizes key influences (red arrows) on development of multimorbidity and illustrates the shared pathways to development of multimorbidity. Mechanisms underpinning development of multimorbidity are frequently inter-related and may be synergistic (black arrows). Mechanisms can be considered in three areas (black ovals): 1) Underlying biological mechanisms relating to ageing and inflammation (blue boxes); 2) Broader determinants of health such as socioeconomic, psychosocial and behavioural social determinants (green boxes); and 3) Medication related.

Figure 3. Identifying who needs an approach to care that accounts for multimorbidity.

The Figure emphasises that adaptation of care to account for multimorbidity may be needed because the patient experiences (a) high condition burden and/or because they experience (b) high treatment burden. (a) Condition burden is related to the severity and complexity of impact of individual conditions, but also to how they interact. For example, diabetes and hypertension is a combination where the combination is relatively unproblematic, whereas combinations like diabetes, schizophrenia and chronic obstructive pulmonary disease have more complex interactions. (b) Treatment burden is related to the impact of treatments, including the complexity of follow-up in relation to the number of different professionals, services, appointments and admissions, and complexity of treatment particularly in relation to polypharmacy. Adapted from.

Figure 4. Treatment burden vs. capacity in patients with multimorbidity.

Multimorbidity is often associated with high treatment burden, while the patients might have lower capacity to self-manage and cope with their situation. Treatment burden refers to the workload of self-management and the health care we ask people to undertake, which is strongly associated with the number of chronic conditions.^, Patient reported measures of treatment burden now exist^– but their ability to predict adverse outcomes remains uncertain. The individual’s capacity to self-manage can vary over time as illnesses accumulate and personal circumstances may change.^,,,, These include the work involved in taking medicines, self-monitoring, attending appointments and following health professional recommendations.