The association between multimorbidity and mobility disability-free life expectancy in adults aged 85 years and over: A modelling study in the Newcastle 85+cohort

Background Mobility disability is predictive of further functional decline and can itself compromise older people's capacity (and preference) to live independently. The world's population is also ageing, and multimorbidity is the norm in those aged >= 85. What is unclear in this age group, is the influence of multimorbidity on (a) transitions in mobility disability and (b) mobility disability-free life expectancy (mobDFLE). Methods and findings Using multistate modelling in an inception cohort of 714 85-year-olds followed over a 10-year period (aged 85 in 2006 to 95 in 2016), we investigated the association between increasing numbers of long-term conditions and (1) mobility disability incidence, (2) recovery from mobility disability and (3) death, and then explored how this shaped the remaining life expectancy free from mobility disability at age 85. Models were adjusted for age, sex, disease group count, BMI and education. We defined mobility disability based on participants' self-reported ability to get around the house, go up and down stairs/steps, and walk at least 400 yards; participants were defined as having mobility disability if, for one or more these activities, they had any difficulty with them or could not perform them. Data were drawn from the Newcastle 85+ Study: a longitudinal population-based cohort study that recruited community-dwelling and institutionalised individuals from Newcastle upon Tyne and North Tyneside general practices. We observed that each additional disease was associated with a 16% increased risk of incident mobility disability (hazard ratio (HR) 1.16, 95% confidence interval (CI): 1.07 to 1.25, p < 0.001), a 26% decrease in the chance of recovery from this state (HR 0.74, 95% CI: 0.63 to 0.86, p < 0.001), and a 12% increased risk of death with mobility disability (HR: 1.12, 95% CI: 1.07- to.17, p < 0.001). This translated to reductions in mobDFLE with increasing numbers of long-term conditions. However, residual and unmeasured confounding cannot be excluded from these analyses, and there may have been unobserved transitions to/from mobility disability between interviews and prior to death. Conclusions We suggest 2 implications from this work. (1) Our findings support calls for a greater focus on the prevention of multimorbidity as populations age. (2) As more time spent with mobility disability could potentially lead to greater care needs, maintaining independence with increasing age should also be a key focus for health/social care and reablement services. Author summary Why was this study done? Multimorbidity is the norm in growing older populations. Mobility disability also has profound consequences for health, well-being and independent living. However, there is a dearth of research exploring the relationship between multimorbidity and mobility disability in those aged.85, even though attention is now more focussed on the quality of remaining life expectancy. What did the researchers do and find? In an inception cohort of 85-year-olds followed over 10 years (age 85 to 95), we explored the association between multimorbidity and transitions in mobility disability, and then examined how this was associated with mobility disability-free life expectancy (mobDFLE). We found that there is no threshold beyond which multimorbidity becomes disabling in those aged.85; rather, each additional disease is associated with a 16% increased risk of incident mobility disability. This translates to reductions in mobDFLE with increasing numbers of long-term conditions. What do these findings mean? Our findings suggest that, in those aged.85, multimorbidity is an important determinant of mobility disability and the number of years spent living with it. As mobility disability can lead to greater care needs, preventing multimorbidity and maintaining independence including from earlier in the life course could be beneficial.

Automated summary

This study found that multimorbidity is a significant determinant of mobility disability and the number of years spent living with it in individuals aged 85 and older. Increasing long-term conditions were associated with a higher risk of incident mobility disability, reduced chances of recovery from this state, and an increased risk of death with mobility disability. The findings highlight the importance of preventing multimorbidity and maintaining independence in older populations.