BACKGROUND: Current applications of @entity79 ( @entity79 ) data in age studies are not free of certain drawbacks. Since it is well established that age-related patterns of @entity79 changes involve three distinct periods (bone acquisition in youth, stabilization at maturity, and decrease with ageing), adjusting for age via an inappropriate mathematical function may lead to inconsistencies and wrong conclusions. HYPOTHESIS: The piecewise model, which encompasses the above three periods, will accurately describe the @entity79 on age. OBJECTIVE: To examine age-related patterns of @entity79 changes using a number of possible mathematical functions and to find among them the best-fitting function. Next, to test whether the chosen function is universally applicable or if there are diverse population-specific functions. MATERIAL AND METHODS: Thirteen ethnic samples from various regions of Europe and Asia, assigned into five ethnic-geographic groups, were examined. The total sample included 2430 males and 2515 females. Compact @entity79 of hand phalanges was measured by photodensitometry from plain radiographs of each individual studied. Statistical software was developed for the purposes of the present study; this software gave a maximum likelihood of the parameter estimates for various statistical models (functions). RESULTS: In all samples of sufficient size and representative age range, a two-interval function was found as the best fitting and most parsimonious model to describe the @entity79 age-related changes. This two-interval function was characterized by age-related bone mass increase, positive slope beta(1s) in young age or a plateau (beta(1s) = 0, i.e. no age-related changes) until a sex-specific age threshold, T(0), after which annual @entity604 ensued with a slope coefficient beta(2s). Threshold of @entity604 in @entity1 of different ethnic groups ranged between 37.85 and 47.77 years, and roughly coincided with perimenopausal age. In males, the age T(0) varied between 27.85 and 49.07 years. The ensuing cortical @entity604 appeared to be linear in both sexes, averaging between 0.51% and 1.15% in @entity1 and between 0.74% and 1.77% per year of young age @entity79 value in females. CONCLUSIONS: The change of phalangeal @entity79 with age may be best described by a two-interval function, regardless of sex and ethnic background. However, specific parameter estimates depend both on gender and ethnic affiliation. This study has yielded a well-fitted model of @entity79 on age suitable for further use in population studies.

Modelling of age-related XXXX using cross-sectional data.

@entity1 :: ('9606', 'Species') :: ['women', 'men'] @entity79 :: ('MESH:D001847', 'Disease') :: ['BMD dependence', 'bone mineral density', 'BMD'] @entity604 :: ('MESH:D016301', 'Disease') :: ['bone loss', 'BMD loss']
@entity604 :: (MESH:D016301,Disease) :: ['bone loss']
