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Positive effects of weight bearing exercises & hormone replacement therapy (HRT) on postmenopausal women

This Wikibooks page is an analysis of the research article "Additive Effects of Weight-Bearing Exercise and Oestrogen on Bone Mineral Density in Older Women " by Kohrt et.al. (1995).

What is the background?

Osteoporosis is defined as an abnormal reduction in bone mineral density. Osteoporosis is caused by the imbalance of bone formation and bone reabsorption, which can be brought upon by the inhibition of new bone formation or excessive bone reabsorption or both occurring simultaneously.

A major factor leading to osteoporosis is the lack of oestrogen in women, which is more likely to affect women over the age of 60 years old. Menopause is accompanied by a reduction in oestrogen levels and therefore increases the risk of osteoporosis in older women. Additionally, there are other factors which contribute to osteoporosis such as insufficient calcium, vitamin D intake and the lack of weight/resistance based exercise. Hormonal imbalances or organ dysfunction can also cause the degeneration of bone mass density .

According to the International Osteoporosis Foundation, universally osteoporosis causes nearly 9 million fractures yearly. These significant statures results in osteoporosis related fractures every 3 seconds. Approximately 200 million women worldwide are affected with osteoporosis, with the majority of these women being aged 60 years or older. Percentages of women with osteoporosis increases with age. At 60 years of age one-tenth of women have osteoporosis and by 90 years of age two-thirds of women have osteoporosis. The most common injury in the older population is hip fractures, with over 80% of hip fractures from individuals that are 65 years of age or older. 75% of hip fractures are from females population. Accompanying hip fractures is the increased mortality rates, and the wellbeing and quality of life is significantly reduced once a fracture has occurred. Along with hip fracture comes chronic pain, infection, weaker immune system and potential permanent disability.

Hormone replacement therapy is common for postmenopausal women who suffer from osteoporosis. Oestrogen has shown to reduce the rate of bone resorption in postmenopausal women and prevent fractures of both hip and vertebral by approximately 30%. However, there are complications with HRT, which can lead to increased risk of coronary heart disease by 30% (CHD), breast cancer by 30% and stroke by 40%.

Physical activity has been shown to benefit postmenopausal women and significantly increase/maintain bone mineral density ^[8]. Studies show that postmenopausal women also benefited from reduction in body fat and increased muscle mass. This led to an increase in energy levels and better quality of life. Physical activity leads to better proprioception which also prevents chances of sudden falls that cause fractures .

Where is this research from?

This research study was carried out at the Applied Physiology section of the General Clinical Research Centre and the Diabetes Research and Training Centre of the Washington University School of Medicine, Department of Internal Medicine, St. Louis, Missouri, By WENDY M. KOHRT, DAVID B. SNEAD, EDUARDO SLATOPOLSKY,2 and STANLEY J. BIRGE, JR. with support from the NIH research grant, General clinical research grant and the Diabetes research and training centre grant.

What kind of research was this?

The research was a clinical trial with research support from the U.S. government. The study was conducted over a period of 11 months with 32 female subjects aged between 60 - 72 years old. The research looked at the effects of physical exercise and hormone replacement therapy (HRT) on bone mineral density in the proximal femur, lumbar spine, wrist and total body .

What did the research involve?

This clinical trial/research involved looking at the effects of weight bearing exercises and oestrogen through hormone replacement therapy (HRT) on post menopausal women. By observing the effects it has on bone mineral density at regions such as the proximal femur, lumbar spine, wrist and total body, it provides an indicator as to how effective weight bearing exercise and HRT is on osteoporosis. The research aimed at looking at weight bearing exercise and HRT individually and in combination. This provides a better understanding as to whether weight bearing exercise and HRT work better synergistically or individually .

The clinical trial/research had the following criterions:

• Participants same sex (female) above age of 60 years old;
• Data provided for variables such as proximal femur BMD, lumbar spine BMD, wrist and total body BMD;
• Clinical trial lasted for 11 months;
• Controlled group present for comparisons; and
• Exercise intensity and duration increased with time.

What were the basic results?

Researchers found changes in bone mass density (BMD) in the femoral neck, lumbar spine and wards triangle was significantly higher in those in the weight bearing exercise group than those in the controlled group. BMD in the HRT group was also higher than the controlled group in femoral neck, lumbar spine and wards triangle, and the BMD in the exercised group was slightly higher than those of the HRT group at the femoral neck and trochanter of the femur and the BMD from combination of exercise and HRT was highest.

Reduction in serum levels of osteocalcin suggests that there is a decreased bone turnover (less bone resorption and more bone formation). This was indicated by increased levels of BMD in response to exercise and HRT. No changes in serum osteocalcin and IGF-I in response to weight bearing exercise suggests that increases in BMD was due to a decreased level of bone resorption and not increased formation.

Results indicate that in combination, weight bearing exercise and HRT is an effective strategy in prevention of osteoporosis. Furthermore, adaptation of physical exercise will increase strength and proprioception, thus reducing the rate of falls causing fractures.

What conclusions can we take from this research?

The conclusion from this clinical trial suggests that weight bearing exercise and HRT can increase BMD, counteract osteoporosis and also prevents reduction in BMD. Weight bearing exercise and HRT individually prevent reduction in BMD, however synergistically their effects are stronger in the prevention of osteoporosis. The lumbar spine, femoral neck, trochanter and ward's triangle all had increased in BMD with the exception of the wrist in all groups (exercise group, HRT group, exercise + HRT group and controlled).

Practical advice

• Individuals suffering from osteoporosis should contact a physician for information regarding HRT and begin a tailored weight bearing exercise program.
• Individuals who do no suffer from osteoporosis should begin weight bearing exercise to increase BMD throughout their life.
• Consult a physician about HRT as it can lead to other complications such as coronary heart disease and increased risk of breast cancer.

Further information/resources

Possible dangers of Hormone Replacement Therapy (HRT)

Oestrogen is a hormone which prevents the increase rate of bone turnover and prevents bone resorption. The Womens Health Initiative suggests that long-term risks of HRT potentially outweighs the benefits. A large study was conducted on postmenopausal women between 60-69 years of age and through HRT there was an associated 30% increased risk of coronary heart disease, breast cancer and 40% increase in stroke. This analysis was supported by another study where the increased risk in breast cancer was much less in women who have never been exposed to HRT.

This suggests that ultimately the best option in prevention of osteoporosis is weight bearing exercise as there are no negative side effects. Weight bearing exercise has also been shown to improve strength and proprioception preventing risks of falls, as previously discussed.