The impact of depression on the morbidity and mortality of &gt;85-year-olds in New Zealand

Grace Pearson; Ngaire Kerse; Simon Moyes; Marama Muru-Lanning; Ruth Teh

doi:10.7861/clinmedicine.19-2-s99

Aims

New Zealand (NZ) has an ageing population, with the population of >85-year-olds projected to quadruple in size by 2068. Over 20% of older adults suffer from a neuropsychiatric disorder, of which depression is the most common. Later-life depression is independently associated with a 41% increased risk of all-cause mortality, and it is the leading cause of disability worldwide. With such an impact on physical health, it is unsurprising, therefore, that depression doubles hospitalisation rates and length of stay in older people.

Methods

Data was collected as part of the ‘Life and Living in Advanced Age Cohort Study’ (LiLACS), for which a detailed study protocol has already been published. Participants were assessed for depression using the Geriatric Depression Scale (GDS), and a score of >5 was classed as depression.

Aims

Determine the prevalence of depression in two cohorts of Maori and non-Maori people aged >85.
Establish the impact of depression on mortality and morbidity (hospitalisation and length of stay).
Compare these outcomes with those of cardiovascular diseases (CVD), and establish the impact of co-morbid depression in CVD.

Results

The overall prevalence of depression across both cohorts at baseline was 34%, which did not differ significantly with ethnicity or gender. The overall prevalence of CVD was 67%, of which 40% had comorbid depression.

Participants with neither CVD nor depression had the best 5-year survival rates, and those with CVD and comorbid depression had the worst. Remarkably, the mortality risk associated with depression was higher than for CVD (56% vs 38%), however when CVD and depression were compounded the mortality risk more than doubled.

Hospitalisation rates were consistently higher in participants with depression than those without depression across all waves of the study, and they stayed an average of 2.3 extra nights in hospital. Comorbid depression in participants with CVD was a significant predictor of hospitalisation and length of stay.

Conclusion

The prevalence of depression in our study was much higher than existing data in NZ, but consistent with estimates of the prevalence of sub-threshold depression in the elderly. This work joins the growing body of evidence that depression has a major adverse impact on the physical health of older people. Therefore, identification and management of depression in the elderly could have a massive positive impact on patients’ psychological and physical wellbeing, thus reducing morbidity, mortality and healthcare costs.