title: Occurrence of medical co-morbidity in mild cognitive impairment: implications for generalisation of MCI research.
abstract: BACKGROUND
  diagnosis of mild cognitive impairment (MCI) typically excludes individuals with medical co-morbidity. Interest in MCI screening raises the questions of what are the best criteria to identify a representative sample and what factors are associated with MCI progression to dementia.
  
  
  OBJECTIVE
  to compare the pattern of disease co-morbidity across different cognitive groups and to examine the role of health co-morbidity as a risk factor for dementia progression from MCI.
  
  
  METHODS
  individuals from the MRC Cognitive Function and Ageing Study were classified as having no cognitive impairment (NCI), MCI, other cognitive impairment no dementia (OCIND) or dementia. At 2 years dementia status was assessed.
  
  
  RESULTS
  over 50% of individuals in each group reported one or more medical condition. The pattern of disease prevalence was similar in the NCI, MCI and OCIND groups. Anaemia was the only health factor associated with an increased risk of dementia progression from MCI.
  
  
  CONCLUSIONS
  classification of MCI using medical exclusions would exclude the majority of the population from a MCI diagnosis. This has implications for treatment decisions and clinical trial recruitment. This could not only make recruitment more difficult but also limit the generalisability of trial results. Medical co-morbidity does not help to distinguish progressive from non-progressive MCI.
authors.affiliation: Department of Public Health and Primary Care, Institute of Public Health, Cambridge University, UK. bcms2@cam.ac.uk
authors.forename: Blossom C M
authors.initials: BC
authors.lastname: Stephan
authors.forename: Carol
authors.initials: C
authors.lastname: Brayne
authors.forename: George M
authors.initials: GM
authors.lastname: Savva
authors.forename: Fiona E
authors.initials: FE
authors.lastname: Matthews
mesh_terms: D000367:Age Factors; D000368:Aged; D000375:Aging; D000704:Analysis of Variance; D000740:Anemia / Q000453:epidemiology; D035843:Biomedical Research; D016009:Chi-Square Distribution; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D015897:Comorbidity; D003704:Dementia / Q000453:epidemiology* / Q000523:psychology; D018450:Disease Progression; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D015995:Prevalence; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology