title: Multimorbidity and health-related quality of life in the older population: results from the German KORA-age study.
abstract: BACKGROUND
  Multimorbidity in the older population is well acknowledged to negatively affect health-related quality of life (HRQL). Several studies have examined the independent effects of single diseases; however, little research has focused on interaction between diseases. The purpose of this study was to assess the impact of six self-reported major conditions and their combinations on HRQL measured by the EQ-5D.
  
  
  METHODS
  The EQ-5D was administered in the population-based KORA-Age study of 4,565 Germans aged 65 years or older. A generalised additive regression model was used to assess the effects of chronic conditions on HRQL and to account for the nonlinear associations with age and body mass index (BMI). Disease interactions were identified by a forward variable selection method.
  
  
  RESULTS
  The conditions with the greatest negative impact on the EQ-5D index were the history of a stroke (regression coefficient -11.3, p < 0.0001) and chronic bronchitis (regression coefficient -8.1, p < 0.0001). Patients with both diabetes and coronary disorders showed more impaired HRQL than could be expected from their separate effects (coefficient of interaction term -8.1, p < 0.0001). A synergistic effect on HRQL was also found for the combination of coronary disorders and stroke. The effect of BMI on the mean EQ-5D index was inverse U-shaped with a maximum at around 24.8 kg/m².
  
  
  CONCLUSIONS
  There are important interactions between coronary problems, diabetes mellitus, and the history of a stroke that negatively affect HRQL in the older German population. Not only high but also low BMI is associated with impairments in health status.
authors.affiliation: Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Institute of Health Economics and Health Care Management, Neuherberg, Germany. matthias.hunger@helmholtz-muenchen.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Hunger
authors.forename: Barbara
authors.initials: B
authors.lastname: Thorand
authors.forename: Michaela
authors.initials: M
authors.lastname: Schunk
authors.forename: Angela
authors.initials: A
authors.lastname: Döring
authors.forename: Petra
authors.initials: P
authors.lastname: Menn
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
authors.forename: Rolf
authors.initials: R
authors.lastname: Holle
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002908:Chronic Disease / Q000453:epidemiology / Q000523:psychology*; D015897:Comorbidity; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008390:Markov Chains; D009010:Monte Carlo Method; D011788:Quality of Life; D012044:Regression Analysis; D057566:Self Report; D012737:Sex Factors; D018434:Sickness Impact Profile