Epidemiology of rib fractures in older men: Osteoporotic Fractures in Men (MrOS) prospective cohort study

Abstract

Objective: To study the causes and consequences of radiologically confirmed rib fractures (seldom considered in the context of osteoporosis) in community dwelling older men.

Design: Prospective cohort study (Osteoporotic Fractures in Men (MrOS) Study).

Setting and participants: 5995 men aged 65 or over recruited in 2000-2 from six US sites; 99% answered mailed questionnaires about falls and fractures every four months for a mean 6.2 (SD 1.3) year follow-up.

Main outcome measures: New fractures validated by radiology reports; multivariate Cox proportional hazard ratios were used to evaluate factors independently associated with time to incident rib fracture; associations between baseline rib fracture and incident hip and wrist fracture were also evaluated.

Results: The incidence of rib fracture was 3.5/1000 person years, and 24% (126/522) of all incident non-spine fractures were rib fractures. Nearly half of new rib fractures (48%; n=61) followed falling from standing height or lower. Independent risk factors for an incident rib fracture were age 80 or above, low bone density, difficulty with instrumental activities of daily living, and a baseline history of rib/chest fracture. Men with a history of rib/chest fracture had at least a twofold increased risk of an incident rib fracture (adjusted hazard ratio 2.71, 95% confidence interval 1.86 to 3.95), hip fracture (2.05, 1.33 to 3.15), and wrist fracture (2.06, 1.14 to 3.70). Only 14/82 of men reported being treated with bone specific drugs after their incident rib fracture.

Conclusions: Rib fracture, the most common incident clinical fracture in men, was associated with classic risk markers for osteoporosis, including old age, low hip bone mineral density, and history of fracture. A history of rib fracture predicted a more than twofold increased risk of future fracture of the rib, hip, or wrist, independent of bone density and other covariates. Rib fractures should be considered to be osteoporotic fractures in the evaluation of older men for treatment to prevent future fracture.

Fig 1 Cumulative incidence of rib fracture among men with and without baseline history of rib fracture (n=5879), MrOS Study

Fig 2 Adjusted hazard ratio and 95% confidence interval for baseline history of rib fracture (n=5879) in MrOS Study. Adjusted for hip bone mineral density, age ≥80, arthritis, and difficulty with five instrumental activities of daily living. Among all locations for a non-spine fracture combined, eight fracture locations accounted for 70% of fractures: 106 first incident fractures occurred in the rib, 85 in the hip, 54 at the ankle, 29 at the wrist, 29 at the clavicle, 28 in the arm, 28 in the foot, and 24 in the fingers. Adjusted hazard ratios were 1.85 (95% CI 1.52 to 2.26) for any fracture, 2.06 (1.14 to 3.70) for wrist fracture, 2.05 (1.33 to 3.15) for hip fracture, and 2.71 (1.86 to 3.95) for rib fracture