Bone Density Loss

Question

1. Do you have any data on average or expected loss of bone density (expressed in percentage) as a result of natural ageing (i.e. say at age 40 vs. 50 or 60?).
2. Can following a strength training regime INCREASE bone density, or will it more likely only maintain/prevent loss.

I have a female client, age 42, excellent physical condition, who follows a healthy exercise program. She strength trains 2x/week and has been for a few years. A recent bone density test showed a loss of 10%. She felt very discouraged by this and informed me that she expected an increase if anything.

I have had difficulty finding literature/studies that dealing with this issue that contained measurable data. Any information you can give me would be much appreciated.

Answer

1. In women, about .3% of bone mineral content is lost each year between the achievement of peak bone mass and menopause. After menopause the rate of loss increases to 2 1/2% to 3% yearly. (Kaplan 1995) In the spine and femur about 20 and 25% of BMD is lost between age 40 and 70 (Mazess R, Bone and Mineral 1987)
2. Exercise in adults is most likely beneficial from its ability to decrease BMD loss, however, it can increase BMD a small amount (1-3%). It is especially small when compared to the effects of exercise on BMD in youths. This increase in BMD seen in exercisers seems to last until the 70s when the amount of BMD in exercising individuals is not different from non-exercisers (Karlsson MK, Lancet 2000; Karlsson MK, Calcif Tissue Int 1995). Continued exercise will prolong its benefits.

One suggestion for the difference in fracture rates shown in epidemiological studies between exercisers and non-exercisers is that the exercisers are less likely to lose balance and have a fall that results in injury. Thus a good stability/core program may benefit a person seeking to avoid broken bones regardless of its effect on BMD.