title: Older participants are frequently excluded from Parkinson's disease research.
abstract: BACKGROUND
  The exclusion of older participants from clinical research is common and limits the generalisation of research findings. We aimed to assess the current potential for older patients to participate in Parkinson's disease (PD) research.
  
  
  METHODS
  We performed a systematic analysis of data extracted from the World Health Organization Clinical Trials Registry Platform regarding 206 actively recruiting PD research studies. Data regarding study variables and exclusion on the grounds of an upper age limit was extracted from each registry entry and subsequently used for statistical analysis.
  
  
  RESULTS
  Exclusion by arbitrary upper age limit is common, with 101 (49%) of studies excluding participants by age and with a mean upper age limit for exclusion of 79.3 years (range 64-95 years). Exclusion by age was significantly more common in studies with an estimated enrollment of fewer than 100 participants; OR 1.92 (95%CI 1.13-3.42) P = 0.018. Rates of exclusion by age were not significantly influenced by study subject, study location, source of funding, study duration or number of centres.
  
  
  CONCLUSIONS
  Exclusion of participants from PD research on the basis of an upper age limit is common and particularly problematic in smaller studies. The exclusion of older participants seriously compromises the generalisation of findings from PD research to the large numbers of elderly PD patients seen in clinical practice.
authors.affiliation: Movement Disorders Service, Clinical Gerontology, Royal Liverpool and Broadgreen University Hospitals Trust, Liverpool L7 8XP, UK. paulrfitzsimmons@gmail.com
authors.forename: P R
authors.initials: PR
authors.lastname: Fitzsimmons
authors.forename: S
authors.initials: S
authors.lastname: Blayney
authors.forename: S
authors.initials: S
authors.lastname: Mina-Corkill
authors.forename: G O
authors.initials: GO
authors.lastname: Scott
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D035843:Biomedical Research; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000628:therapy*; D016032:Randomized Controlled Trials as Topic; D012042:Registries; D012107:Research Design; D018401:Sample Size; D018709:Statistics, Nonparametric; D013997:Time Factors