title: Scalability and internal consistency of the German version of the dementia-specific quality of life instrument QUALIDEM in nursing homes - a secondary data analysis.
abstract: BACKGROUND
  Quality of life (Qol) is a widely selected outcome in intervention studies. The QUALIDEM is a dementia-specific Qol-instrument from The Netherlands. The aim of this study is to evaluate the scalability and internal consistency of the German version of the QUALIDEM.
  
  
  METHODS
  This secondary data analysis is based on a total sample of 634 residents with dementia from 43 nursing homes. The QUALIDEM consists of nine subscales that were applied to a subsample of 378 people with mild to severe dementia and six consecutive subscales that were applied to a subsample of 256 people with very severe dementia. Scalability, internal consistency and distribution scores were calculated for each predefined subscale using the Mokken scale analysis.
  
  
  RESULTS
  In people with mild to severe dementia, seven subscales, care relationship, positive affect, negative affect, restless tense behavior, positive self-image, social relations and feeling at home, were scalable (0.31 ≤ H ≤ 0.65) and internally consistent (Rho ≥ 0.62). The subscales social isolation (H = 0.28) and having something to do (H = 0.18) were not scalable and exhibited insufficient reliability scores (Rho ≤ 0.53). For people with very severe dementia, five subscales, care relationship, positive affect, restless tense behavior, negative affect and social relations, were scalable (0.33 ≤ H ≤ 0.65), but only the first three of these subscales showed acceptable internal consistency (Rho 0.59 - 0.86). The subscale social isolation was not scalable (H = 0.20) and exhibited poor internal consistency (Rho = 0.42).
  
  
  CONCLUSIONS
  The results show an acceptable scalability and internal consistency for seven QUALIDEM subscales for people with mild to severe dementia and three subscales for people with very severe dementia. The subscales having something to do (mild to severe dementia), negative affect (very severe dementia), social relations (very severe dementia) and social isolation (both versions) produced unsatisfactory results and require revision.
authors.affiliation: German Center for Neurodegenerative Diseases DZNE, Stockumer Straße 12, 58453 Witten, Germany. Martin.Dichter@dzne.de
authors.forename: Martin Nikolaus
authors.initials: MN
authors.lastname: Dichter
authors.forename: Olga
authors.initials: O
authors.lastname: Dortmann
authors.forename: Margareta
authors.initials: M
authors.lastname: Halek
authors.forename: Gabriele
authors.initials: G
authors.lastname: Meyer
authors.forename: Daniela
authors.initials: D
authors.lastname: Holle
authors.forename: Johanna
authors.initials: J
authors.lastname: Nordheim
authors.forename: Sabine
authors.initials: S
authors.lastname: Bartholomeyczik
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D003704:Dementia / Q000175:diagnosis / Q000451:nursing / Q000523:psychology*; D003858:Dependency, Psychological; D005163:Factor Analysis, Statistical; D005260:Female; D005858:Germany; D006801:Humans; D007398:Interpersonal Relations; D008297:Male; D009426:Netherlands; D009735:Nursing Homes; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*