title: Implementation of the simplified stochastic model of ageing for longitudinal osteoarthritis data assessment.
abstract: BACKGROUND
  Occurrence and progression of age-related irreversible degradations of skeletal joints, osteoarthritis (OA), has a stochastic nature. However, it is commonly described using polynomial models, which may not necessarily be optimal.
  
  
  OBJECTIVE
  To implement a stochastic model of gradual accumulation of the distinct changes for estimating individuals' putative age at onset and risk of the process advancing in the OA longitudinal data.
  
  
  METHODS
  The model was formulated as a discrete Markov process. It was applied to radiographic knee osteoarthritis (RKOA) data: 243 Kellgren-Lawrence (K/L) and 207 osteophytes (OP) score histories from the 15-year follow-up Chingford study.
  
  
  RESULTS
  The model performance was examined in Monte-Carlo simulations. The mean age at onset of knee osteoarthritis was: 53.04 and 53.23 years and the average annual risk of one K/L and one OP grade appearance was: 0.066 and 0.025, respectively. The analysis also suggested that there is 3-4 years difference between the inferred age at onset and the age when knee osteoarthritis becomes detectable on radiograph.
  
  
  CONCLUSIONS
  The stochastic model provides more accurate description of the empiric data compared with the corresponding polynomial model. The model-based individual's estimates could be used as an important tool to fit age-related patterns of the corresponding diseases and conditions.
authors.affiliation: Human Population Biology Research Unit, Department of Anatomy and Anthropology, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Michael
authors.initials: M
authors.lastname: Korostishevsky
authors.forename: Frances
authors.initials: F
authors.lastname: Williams
authors.forename: Deborah
authors.initials: D
authors.lastname: Hart
authors.forename: Orit
authors.initials: O
authors.lastname: Blumenfeld
authors.forename: Timothy
authors.initials: T
authors.lastname: Spector
authors.forename: Gregory
authors.initials: G
authors.lastname: Livshits
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology*; D003198:Computer Simulation; D018450:Disease Progression; D005260:Female; D006801:Humans; D007596:Joints / Q000473:pathology; D008131:London / Q000453:epidemiology; D008137:Longitudinal Studies; D008875:Middle Aged; D008954:Models, Biological; D009010:Monte Carlo Method; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000473:pathology; D011859:Radiography; D013223:Statistics as Topic; D013269:Stochastic Processes