Dynamics of multimorbidity and frailty, and their contribution to mortality, nursing home and home care need: A primary care cohort of 1 456 052 ageing people

Abstract

Background: Prevalence of both multimorbidity and frailty increases with age, but more evidence is needed to elucidate their relationship and their association with other health-related outcomes. We analysed the dynamics of both conditions as people age and calculate the associated risk of death, nursing home admission, and need for home care.

Methods: Data were drawn from the primary care electronic health records of a longitudinal cohort of people aged 65 or older in Catalonia in 2010-2019. Frailty and multimorbidity were measured using validated instruments (eFRAGICAP, a cumulative deficit model; and SNAC-K, respectively), and their longitudinal evolution was described. Cox regression models accounted for the competing risk of death and adjusted by sex, socioeconomical status, and time-varying age, alcohol and smoking.

Findings: We included 1 456 052 patients. Prevalence of multimorbidity was consistently high regardless of age, while frailty almost quadrupled from 65 to 99 years. Frailty worsened and also changed with age: up to 84 years, it was more related to concurrent diseases, and afterwards, to frailty-related deficits. While concurrent diseases contributed more to mortality, frailty-related deficits increased the risk of institutionalisation and the need for home care.

Interpretation: The nature of people's multimorbidity and frailty vary with age, as does their impact on health status. People become frailer as they age, and their frailty is more characterised by disability and other symptoms than by diseases. Mortality is most associated with the number of comorbidities, whereas frailty-related deficits are associated with needing specialised care.

Funding: Instituto de Salud Carlos III through PI19/00535, and the PFIS Grant FI20/00040 (Co-funded by European Regional Development Fund/European Social Fund).

Keywords: Aging; Cohort; Frailty; Mortality; Multimorbidity; Primary health care.

Figure 1

Flow chart of the study population. The figure reports the number of individuals who met each exclusion criterion, as well as the number of individuals that met all the criteria (unique IDs).

Figure 2

Dynamics of frailty and multimorbidity with age. Complete population, and stratified by sex. Note: Multimorbidity is described as the percentage of the population that was multimorbid at each timepoint. A person was considered multimorbid if they had active diagnoses belonging to two or more distinct SNAC-K disease categories. The rest of variables are described as median interquartile range. Deficit were divided into two categories: disease-related deficits and deficits related to symptoms/signs, laboratory, and disability (SSLD). The dashed blue line represents the number of deficits from which the individual would be considered frail. Data from people aged 100 or more are aggregated. F: women; M: men. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Figure 3

Mosaic plot showing the flow of the combination of frailty plus multimorbidity in included patients at each age. Note: A person was considered as multimorbid if they had active diagnoses in two or more distinct SNAC-K disease categories, and frail if they had a frailty index $\ge$ 0.12. In mosaic plots, the area of each box corresponds to the proportion of persons included in each category. Data from registers aged 100 or more are aggregated.

Figure 4

Number of deficits of each type by frailty category. Note: The distributions of the number of deficits were compared within frailty class using a Mann-Whitney-Wilcoxon test. All differences were significant ($p$-value $<$ 0.001).