Health Impact of Osteoporosis

Abstract

Osteoporosis constitutes a major public health problem through its association with age related fractures. These fractures typically occur at the hip, spine and distal forearm. It has been estimated from incidence rates derived in North America that the lifetime risk of a hip fracture in Caucasian women is 17.5%, with a comparable risk in men of 6%. Hip fractures lead to an overall reduction in survival of around 15% and the majority of excess deaths occur within the first six months following the fracture. They are also associated with considerable morbidity: they invariably necessitate hospitalization and the average length of hospital stay is around 30 days. Although all vertebral deformities do not come to clinical attention, the lifetime risk of clinically diagnosed vertebral fractures is around 15% in Caucasian women. These fractures tend to be associated with back pain and result in kyphosis. They are also associated with impairment of survival, although this is likely to be due to the clustering of comorbidity which predisposes independently to osteoporosis and premature death. Around a quarter of clinically diagnosed vertebral deformities result in hospitalization.Hip fractures typically follow a fall from the standing position and their incidence rises exponentially with age. Above the age of 50 years there is a female to male ratio of around 2:1. There is marked seasonality in hip fracture incidence, with substantial increases in rates during winter months in temperate countries. Nevertheless, the majority of hip fractures follow falls indoors and are not related to slipping on icy pavements. Age- and sex-adjusted hip fracture rates are generally higher in Caucasian than in Asian populations. Furthermore, the pronounced female preponderance in fracture incidence observed in white populations is not seen amongst blacks or Asians in whom age-adjusted female to male incidence ratios approximate unity. Urbanisation in certain parts of Africa has led to a secular increase in hip fracture incidence rates, but even recently derived African rates are considerably lower than those found in North American or European whites. The incidence of clinically diagnosed vertebral fractures also rises steeply with age and the female to male incidence ratio after age adjustment is also around 2:1.The ultimate determinants of osteoporotic fractures are bone strength and trauma. Bone strength is related to the quality of bone, its architecture and its mass. These characteristics cannot easily be assessed in vivo, but correlate closely with bone mineral density. There is now convincing longitudinal evidence that a reduction in bone density is an important determinant of fracture risk. The determinants of bone density can be categorised into those influencing the peak which is attainable during growth and consolidation; and the subsequent rate of bone loss. There is a genetic feeling to the peak bone density which can be obtained during the first 25 years of life, which is modified by nutrition, mechanical factors and hormonal status. Important determinants of bone loss include estrogen deficiency in women, low body mass index, cigarette smoking, alcohol consumption, poor dietary calcium intake, physical inactivity, certain drugs such as corticosteroids, and illnesses such as rheumatoid arthritis. The information on individual risk factors which has been carefully characterised over the last decade permits translation into coherent public health strategies for the prevention of osteoporosis both in individuals and in the general population.