title: The difference between hazard and risk in the relation between bone density and fracture.
abstract: The relation between fracture risk and bone density is frequently defined in terms of a relative hazard derived from the Cox proportional hazards model. The relative hazard is a multiplicative factor representing the rise in hazard for each standard deviation fall in bone mineral density, which has a typical value of about 1.5. It is not generally appreciated that this hazard may only be equated with absolute risk when risk is very low; at higher risk and over long periods, it is inappropriate to apply a multiplicative factor to absolute risk because risk has a range of 0-1 and cannot exceed unity. Here, we show how "hazard" can be converted to risk and how misleading the current practice of equating relative hazards with relative risks can be.
authors.affiliation: Institute of Medical and Veterinary Science, Frome Road, PO Box 14, Rundle Mall, Adelaide, 5000, South Australia, Australia. christopher.nordin@imvs.sa.gov.au
authors.forename: B E Christopher
authors.initials: BE
authors.lastname: Nordin
authors.forename: Peter A
authors.initials: PA
authors.lastname: Baghurst
authors.forename: Andrew
authors.initials: A
authors.lastname: Metcalfe
mesh_terms: D000368:Aged; D015519:Bone Density; D005260:Female; D050723:Fractures, Bone / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D016016:Proportional Hazards Models; D012306:Risk; D018570:Risk Assessment; D013997:Time Factors