A full definition of osteoporosis can be found here. Surface to say that osteoporosis is a skeletal condition that is associated with low bone mineral density and low quality bones, and hence a decrease in bone strength. This weakening of the bone leaves a sufferer susceptible to an increased risk of fracture if falling in an accident.
It is a fairly easy process for a doctor to measure the bone mineral density of a patient. The bone mineral density is defined as a relative scale of bone loss based upon the density of a healthy young, Caucasian adult reference. When having a bone mineral density (BMD) test what is measured is the difference in standard deviations between the person tested and the reference. If a test shows a BMD T score of between -1 and -2.5 then the person is diagnosed as having osteopenia; if the person does not take steps to rectify the loss of BMD (by exercise, diet or medication) then they are at risk of developing osteoporosis. If a patient as a BMD T score of -2.5 or less then they have full blow osteoporosis. With every decrease in BMD T score of 1, it is estimated that the risk of suffering a bone fracture doubles.
It is well known that bone density decreases as people age (this occurs in both men and women), especially at the time of the menopause. The biology of this phenomenon is discussed elsewhere on the site, as are preventative methods that may help to maintain bone density closer to the norm. The development of osteoporosis or osteopenia is a major concern as it is estimated that as many as four out of every ten women over the age of 50 in the USA (and most likely in other western countries) will suffer a bone fracture, to the wrist, spine or hip in their lifetime. It has been suggested that women who suffer from osteopenia have a 1.8 fold increase in the liklyhood of suffering a bone fracture in comparison with a non-osteopenia person, whilst this increases to four times the risk if a person as osteoporosis. Once an elderly person has suffered a fracture it can have a very negative impact upon their standard of living and may lead to permanent disability. This is because it is generally more difficult for an elderly person to recover from injury.
ReferencesTai Chi part 4