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Income and economic productivity loss associated with comorbidity: longitudinal analysis of linked individual-level data for a whole country
  1. Finn Sigglekow1,
  2. Nick Wilson1,
  3. Tony Blakely2
  1. 1 Department of Public Health, University of Otago Wellington, Wellington, New Zealand
  2. 2 Population Interventions, Centre for Epidemiology and Biostatistics, The University of Melbourne School of Population and Global Health, Melbourne, Victoria, Australia
  1. Correspondence to Dr Tony Blakely, Population Interventions, Centre for Epidemiology and Biostatistics, The University of Melbourne School of Population and Global Health, Melbourne, Victoria, Australia; antony.blakely{at}


Objective To estimate the income loss from having two or more diseases, over and above the independent and separate effects of having a single disease.

Methods We used linked health income data from 2006–2007 to 2015–2016 for 25–64 years, for the entire New Zealand population. Fixed effects OLS regression was used to estimate within-individual income loss for diseases separately, and to estimate if having two or more diseases together resulted in reduced (subadditive) or additional (superadditive) income impacts (relative to adding together the income impacts for each disease when experienced singly).

Results Of the 169 comorbidity pairs for both sexes, 28 (17%) had a statistically significant superadditive (n=14) or subadditive (n=14) effect of having two diseases. The combined total income gain from deleting all diseases and comorbidities was US$2.269 billion (95% CI US$$2.125 to US$2.389 billion), or a 3.61% (95% CI 3.38% to 3.80%) increase in income. Of this, 8.8% or US$200 million (95% CI US$193 to US$207 million) was attributable to a tendency for comorbidity interactions to increase income loss more than expected for common disease pairings.

Conclusions This national longitudinal study found that disease is associated with income loss, but most of this impact is due to the distinct and independent impact of separate diseases. Nevertheless, there was a tendency for two or more diseases to disproportionately increase income loss more than the summed impacts of each of these diseases if experienced singly.

  • Life course epidemiology

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  • Contributors All three equally contributed to design of study, interpretation of the results and write up. FS carried out the data analysis.

  • Funding The BODE3 Programme is funded by New Zealand Health Research Council (10/248, 16/443) and the Ministry of Business, Innovation and Employment (UOOX1406)

  • Competing interests None declared.

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

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.