Research suggests that thinner men in middle age, or those who lose substantial weight as they grow older, may have brittle bones in their 70s.

by John Gever, Staff Writer, MedPage Today
 

OSLO, Sept. 19 — Thinner men in middle age, or those who lose substantial weight as they grow older, may have brittle bones in their 70s, researchers here said.

Action Points 
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Explain to interested patients that the study found men who were relatively thin when young or who lost weight as they aged were at increased risk of osteoporosis.

Explain that osteoporosis is a significant problem for older men, though less common than in women.

Explain that several treatment approaches are available for osteoporosis.
Some 15.1% of men who lost 10% or more of their body weight after their late 40s had osteoporosis when they reached 75, compared with 0.6% of those who had weight gains of at least 10%, reported Haakon E. Meyer, M.D., Ph.D., of the University of Oslo, and colleagues in the Aug. 15 issue of the American Journal of Epidemiology.

The researchers, who studied nearly 1,500 men over a 30-year period, found that combination of low initial weight and subsequent weight loss was an even stronger risk factor for osteoporosis.

The prevalence of osteoporosis in the quartile with the lowest baseline body mass index and who later lost at least 5% of body weight was 31% (95% CI 24% to 37%), compared with 4% (95% CI 1% to 7%) for those in the lowest quartile of BMI with weight gains of at least 5%.

“Low BMI in middle-age men was related to the risk of osteoporosis three decades later and … this risk was modulated considerably by later weight change,” Dr. Meyer and colleagues wrote.

They said a clinical implication of their findings is that weight loss, while generally beneficial, is not risk-free. “When considering weight-loss interventions, the effect on osteoporosis and fracture should also be included and, if possible, counteracted,” they suggested.

Slimness and short-term weight loss are already recognized as a risk factor for osteoporosis for men as well as women, the researchers said, but their effects had not previously been studied for such a long period.

The new findings emerged from studies of 1,476 Norwegian men in the cities of Oslo and Tromsø who underwent general health exams from 1972 to 1975 and again from 2000 to 2001. The follow-up screening also included bone mineral density testing of the hip.

Participants were 47 to 49 years old during the first scan and 75 to 77 at the second. The time between exams ranged from 26 to 29 years.

Mean baseline BMI was 24.4 (SD 2.6). At follow-up, mean BMI was 26.5 (SD 3.3), with mean weight change of 5.2% (SD 10.2%).

Weight change was inversely associated with baseline BMI (r = -0.21).

Mean age-adjusted bone mineral density at follow-up was 0.933 g/cm2 in the lowest quartile of baseline BMI, versus 1.024 g/cm2 in the highest quartile.

From the lowest to highest baseline BMI quartiles, the prevalence of osteoporosis was 10.9%, 3.5%, 4.4% and 1.2%, respectively, after adjusting for age and smoking status.

Dr. Meyer and colleagues calculated that total hip bone mineral density increased by 0.029 g/cm2 (95% CI 0.023 to 0.036) for each 10% of weight gain between evaluations.

This result was almost completely unaffected when the researchers excluded more than 800 participants who had serious comorbidities known to affect osteoporosis risk.

They also estimated that men in the lowest quartile of BMI who lost at least 5% of body weight would be 2.79 times as likely to suffer a future hip fracture relative to those in the highest quartile and with stable weight.

“Weight change might act on the skeleton through changes in mechanical loading, changes in mechanical muscle stress, changes in hormone regulation of bone metabolism, and changes in intake of nutrients,” the researchers wrote in addressing possible mechanisms.

Altered smoking habits or physical activity can affect weight as well as osteoporosis risk, they said.

They said a limitation on their analysis was that they did not have actual fracture data for participants nor information on family history of fractures.

Also, the lack of bone mineral density testing at the initial evaluation precluded a direct comparison with weight change over time.


The research was supported by the Research Council of Norway and the Norwegian Foundation for Health and Rehabilitation.
No potential conflicts of interest were reported.

Primary source: American Journal of Epidemiology
Source reference: Meyer H, et al “Weight change over three decades and the risk of osteoporosis in men: the Norwegian epidemiological osteoporosis studies (NOREPOS)” Am J Epidemiol 2008; 168: 454-60. 
Published: September 19, 2008
Reviewed by Zalman S. Agus, MD; Emeritus Professor
University of Pennsylvania School of Medicine. 

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