Osteoporosis

A healthy bone can typically withstand the mechanical stresses placed on it as we move. Osteoporosis is a disease characterised by reduced bone strength and therefore an elevated risk of bone fractures. The reason for the reduced bone strength is partly a reduction in bone mineral density (BMD) and partly a compromised bone microstructure. In Denmark, the disease affects one in three women and one in six men over the age of 50 (1). It is estimated that approximately half a million Danish people are living with undiagnosed
osteoporosis (2). Hip fractures, forearm fractures and vertebral collapse are the most common types of fractures related to osteoporosis. While the first two fractures typically occur after minor trauma (e.g. due to falls), a vertebral compression fracture is the result of ‘fatigue fractures’, which develop when the daily mechanical load repeatedly exceeds the strength of the vertebrae. This is why osteoporosis can be characterised as a “silent disease” that is often first discovered when the patient experiences the first fracture. The incidence of osteoporosis is expected to increase in the coming years due to the increasing
life expectancy of the population (3,4). This will mean an increased financial
burden on society with reduced quality of life for an increasing number of patients who will become dependent on carers and the health service. The disease can be extremely painful and debilitating, with hip fractures in particular being linked to high morbidity and mortality rates. Primary prevention and
health promotion should therefore be a high priority, including community-based training programmes that can strengthen the skeleton, increase muscle strength and improve balance and coordination. Osteoporosis is diagnosed on the basis of a measurement of BMD (as an estimate of bone strength) determined by Dual-energy X-ray Absorptiometry (DXA scan). Like many other physiological variables, 60-80% of BMD is genetically determined. However, implicit in
this is the fact that 20 to 40% of the variation can be attributed to our lifestyles and living conditions; including our levels of physical activity. Epidemiological studies show that bone mineral content (BMC) and BMD increase to a maximum (peak bone mass, PBM) in our mid-twenties, where it reaches a plateau that
lasts until we reach the fifties. Both genders then experience a 0.5-1% decrease
in BMD annually, and in women there is an accelerated decrease of 3-6% annually in the first few years after menopause (cessation of menstruation). This, along with a lower plateau, is probably the main reason for the higher incidence of osteoporosis in women compared to men.