Multimorbidity, activity limitation and self-reported health all predict mortality risk, but better measures were...

With an ageing population, morbidity and multiple health conditions are an increasing public health concern. This study aimed to investigate how morbidity as measured by the Charlson comorbidity index and two morbidity measures; activity limitation and self-reported health, individually and collectively explain the increased risk of mortality with age.

We used the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA) wave one, dataset, a national representative sample of people over 50 years of age, with follow-up until May 31, 2020. Cox proportional hazard regression models were used to assess the associations between a modified Charlson comorbidity index (m-Charlson), self-reported health, activity limitation, and mortality in the Northern Irish cohort.

m-Charlson showed a steeper relationship with age, the proportion of participants with a Charlson of two or more increase from 15.2% (aged 50-59) to 32.0% (aged 80+). All measures of morbidity exhibited a strong relationship with socio-economic status, though the gradients were more marked for self-reported health than for activity limitation or Charlson index. All three morbidity measures were independently related to mortality risk though the associations attenuated with age. However, even in models with all three measures of morbidity, most of the age-related increase in mortality risk remained unexplained.

All three morbidity measures carry separate and independent information about the health status of older people and therefore about mortality risk; it is apparent that it is still worth asking patients how they feel and how their health is affecting their activity. Further research should aim to dissect health trajectories in dynamic prediction models in addition to other measures of health status.