The result for any individual is compared to average values for their age and sex obtained from DXA studies of the general population. Most of the bones' mineral content is laid down in the first twenty to thirty years of life. Once this age is reached you have received your 'quota'. Your bone mineral density will not increase thereafter. On the contrary, after a period of several years' stability, it will begin to decrease at around thirty-five years of age, and given the wrong combination of environmental and genetic influences will almost inevitably result in osteoporosis in old age.
Osteoporosis is indeed one of the most common chronic medical problems in the elderly.
Whether any particular individual develops osteoporosis is influenced by their daily-life factors like smoking, diet, alcohol intake, weight baring exercise, but also by inherited genetic factors. The natural bone loss that occurs with aging is accelerated in women after the menopause because of the changing hormonal picture. If insufficient calcium and other bone minerals are accrued in the first three decades of life maximum bone density achieved will be suboptimal and even the aging process will place any such person at risk of osteoporosis whilst still a relatively young adult. Some researchers have found reduced bone mineral content common at all ages in people with CF, suggesting the importance of decreased accretion of bone mineral content as well as increased loss. The pattern of complications from osteoporosis in older patients with CF has been found to be similar to that in the non-CF population but seen about thirty years earlier.