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Comorbid chronic diseases, discordant impact on mortality in older people: a 14-year longitudinal population study
  1. G E Caughey1,
  2. E N Ramsay2,
  3. A I Vitry1,
  4. A L Gilbert1,
  5. M A Luszcz3,
  6. P Ryan2,
  7. E E Roughead1
  1. 1Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
  2. 2Discipline of Public Health, University of Adelaide, Adelaide, Australia
  3. 3School of Psychology and Flinders Centre for Ageing Studies, Flinders University, Adelaide, Australia
  1. Correspondence to Dr Gillian E Caughey, Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, GPO Box 2471, Adelaide 5001, Australia; gillian.caughey{at}


Objectives To determine the impact of comorbid chronic diseases on mortality in older people.

Design Prospective cohort study (1992–2006). Associations between numbers of chronic diseases or mutually exclusive comorbid chronic diseases on mortality over 14 years, by Cox proportional hazards model adjusting for sociodemographic variables or Kaplan–Meier analyses, respectively.

Setting Population based, Australia.

Participants 2087 randomly selected participants aged ≥65 years old, living in the community or institutions.

Main results Participants with 3–4 or ≥5 diseases had a 25% (95% CI 1.05 to 1.5, p=0.01) and 80% (95% CI 1.5 to 2.2, p<0.0001) increased risk of mortality, respectively, by comparison with no chronic disease, after adjusting for age, sex and residential status. When cardiovascular disease (CVD), mental health problem or diabetes were comorbid with arthritis, there was a trend towards increased survival (range 8.2–9.5 years) by comparison with CVD, mental health problem or diabetes alone (survival 5.8–6.9 years). This increase in survival with arthritis as a comorbidity was negated when CVD and mental health problems or CVD and diabetes were present in disease combinations together.

Conclusion Older people with ≥3 chronic diseases have increased risk of mortality, but discordant effects on survival depend on specific disease combinations. These results raise the hypothesis that patients who have an increased likelihood of opportunity for care from their physician are more likely to have comorbid diseases detected and managed.

  • Comorbidity
  • chronic disease
  • older people
  • mortality
  • ageing RB
  • longitudinal studies
  • morbidity
  • primary healthcare

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  • Funding This work was funded by the Australian Research Council/National Health and Medical Research Council of Australia from an Ageing Well, Ageing Productively Program Grant.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Flinders University and the University of South Australia.

  • Provenance and peer review Not commissioned; externally peer reviewed.