While it is generally agreed that regular exercise enhances mobility and gives a sense of well being, the effect of exercise on bone density in older people is uncertain. Dr John Ward, a geriatrician at the Prince of Wales Hospital in Sydney, has just finished a four-year study of 600 elderly women, examining all aspects of their balance, including strength of limbs, vision and bone density.
The survey, of randomly chosen women aged over 60, showed they continued to lose bone mass each decade after menopause. Hormone replacement therapy—the replacement of estrogen alone or a combination of estrogen and progestogen –is the main treatment for osteoporosis, but has its pros and cons depending on the history of the patient.
Estrogen on its own can cause mood swings and general malaise. When progestogen is added, menstruation will restart, a treatment many women reject. But there are other more important considerations. An Associate Professor at the Austin Hospital, Ego Seeman, said the main risk of long-term hormone replacement therapy was breast cancer, although estrogen therapy might reduce the risk of heart disease. And while estrogen combined with progestogen might reduce the risk of endometrial cancer, estrogen-only therapy in women with intact wombs might increase the risk of endometrial cancer.
Most research has centered on the middle-aged because this is when fractures occur most. However, latest research indicates that it is crucial to develop bone mass in the early, growth years to ensure healthy bones in later life. Professor Seeman said that during the first 20 years, a person could build a kilogram of calcium in his or her body—half of which would be lost over the next 60 years. Bone mass could be viewed as a “bank” in which calcium should be invested early to ensure there would be enough bone left when the process of bone-loss started. He said there were many misconceptions about osteoporosis, especially the emphasis on diet and exercise in the second half of life.
He and Dr George Szmukler, of Royal Melbourne Hospital, have jointly completed a study that showed girls with anorexia nervosa to have similar reduced bone mass to that found in elderly women. The study of 67 girls, published in the Journal of Bone and Mineral Research in December, concluded that early-onset anorexia nervosa was likely to pose a greater risk of bone fractures because sufferers were more deficient in bone density.
The study suggested that hormone replacement therapy could have an important role in the treatment of girls with anorexia nervosa. It also showed that some of the girls with anorexia nervosa who exercised vigorously maintained bone density at the hips. Professor Seeman said surveys generally showed that exercise was most important during growth and development. “By contrast, exercise in adults has not been shown to substantially result in a higher bone density.”
This is contrary to what people would like to believe. However, the evidence is that despite controlled exercise programs of nine to 12 months, bone density in exercising women around the age of 45-50 years makes little difference to the skeleton. There may even be no effect. However, he stressed that exercise was beneficial to older people in promoting well being and maintaining mobility, agility and speed—all important factors in preventing fractures during a fall.
Further research has shown that smoking can lower bone density and increase a person’s chances of developing osteoporosis. One study, by Melbourne University and the Austin Hospital, of 41 sets of female twins—one smoker and one non-smoker–has shown that the women who smoked a packet of cigarettes a day between the ages of 20 and 50 had an eight percent lower bone density than the non-smoking women.
Professor Seeman, who was involved in the study of the twins, said the degree of bone loss in the smoker was equivalent to the smoker having bone-loss for eight more years than a woman of the same age who never smoked. “This degree of bone loss will … substantially increase her risk for fractures,” he said. The Austin Hospital has been chosen as one of the world centers to trial a drug to prevent bone loss and restore bone mass. The hospital is looking for volunteers: post-menopausal women who have osteoporosis and possibly fractures of the spine, and who are not receiving any form of therapy.