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CATIE News - British Columbia study checks for thinning bones

2010 Aug 30 - Thinner-than-normal bones are among the complications that can develop in HIV-positive people. Although this is one aspect of health that may become an issue for many people as they age, in some HIV-positive people decreases in bone mineral density (BMD) seem to be accelerated. In its milder form, decreased BMD is called osteopenia; its more severe form is osteoporosis. Decreased BMD can increase the risk for developing fractures after falls or accidents. Researchers are trying to understand why bone loss is a problem in HIV infection and they are testing ways of halting and reversing it.

A research team in Vancouver at the British Columbia Centre for Excellence in HIV/AIDS conducted a study to assess how common decreased BMD was in a major Canadian clinic. Their findings suggest that at least 20% of HIV-positive people in their clinic have a less-than-normal BMD. The research team also assessed factors that may have played a role in the development of reduced BMD. This is not an easy task, as many factors that contribute to osteopenia and osteoporosis are relatively common in HIV-positive people, such as the following:

  • smoking tobacco
  • alcohol abuse
  • lack of regular exercise
  • low levels of calcium and vitamin D
  • malnutrition
  • low levels of testosterone in men and low levels of estrogen in women
  • use of corticosteroids

Some research has suggested that anti-HIV therapy (commonly called ART or HAART) may also play a role in bone loss. Later in this CATIE News bulletin, we put the B.C. findings in the context of other ongoing research on bones.

Study details

Researchers at St. Paul's Hospital in Vancouver recruited 290 HIV-positive people for this study. The average profile of participants when they enrolled in the study was as follows:

  • 11% females, 89% males
  • age - 49 years
  • 80% were White (the ethno-racial composition of the remaining participants was not released)
  • duration of HIV infection - 11 years
  • 97% of participants took ART
  • ART was used for about five years

All participants underwent low-dose X-ray scans designed to assess bone density. These are called DEXA (dual energy x-ray absorptiometry). Extensive lab analysis of blood samples collected within a month of the DEXA scan were also performed.

Results

Overall, about 20% of participants had thinner-than-normal bones. This was more common in the spine than in the hips of both men and women.

No link between levels of any of the following hormones and reduced BMD was found:

  • parathyroid hormone
  • testosterone
  • TSH (thyroid stimulating hormone)

Many HIV-positive people take medications to help lower cholesterol and blood pressure and deal with other conditions. In theory, these medicines could have an effect on BMD. The B.C. team did not find any link between BMD and the following commonly used medicines:

  • anabolic steroids
  • corticosteroids
  • Crestor (rosuvastatin)
  • Lipitor (atorvastatin)

ART and bone density

Taking into account many factors, including the different types of ART used by participants, the research team found that there was no connection between different anti-HIV drugs and thinning bones.

Results-Size matters

What did affect bone mineral density was a person's body mass index (BMI)-a ratio of their weight to their height. BMI can give a crude assessment of a person's relative fatness or thinness. People who had a less-than-ideal BMI (around 22) were more likely to have thinner-than-normal bones than people who had a BMI within an acceptable range. Indeed the average BMI of people with normal bone mineral density was around 24. This difference in BMI and its relationship to bone thickness was statistically significant.

Although the difference in BMI seems small, what is important is the general trend: thinner people tend to have problems with bone density. This is something that has been found in HIV-negative people. The statistical significance of this finding in the B.C. study may have been greater had there been more people enrolled.

Note that the inverse of the B.C. finding, that overweight people tend to have greater BMD, is not necessarily a healthier trend. Having excess weight is associated with many unhealthy consequences and though the BMD of fat people may be greater than that of skinny people, the quality of the bone architecture may not be as good as in people whose BMI is within a normal range.

Money and design issues

Research is expensive and, given the current economic situation, competition for scarce funding is intense. The present study was of a cross-sectional design. Such studies are useful because they are generally cheaper and faster to conduct than large, long-term studies. However, cross-sectional studies are analogous to a snapshot in time, providing a picture of people's health at only one point in time. Furthermore, cross-sectional studies can find associations but cannot prove cause and effect. The researchers graciously acknowledged the limitations of their study.

Despite these drawbacks, the B.C. study is an important step forward in trying to understand bone health in HIV-positive people.

The next CATIE News report examines a different study design from the United States and its findings on changes in bone mineral density over time in HIV-positive people.

-Sean R. Hosein

REFERENCE:

  1. Guillemi S, Harris M, Bondy GP, et al. Prevalence of bone mineral density abnormalities and related risk factors in an ambulatory HIV clinic population. Journal of Clinical Densitometry . 2010 ; in press.

 

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CATIE-News is written by Sean Hosein, with the collaboration of other members of the Canadian AIDS Treatment Information Exchange, in Toronto.

From Canadian AIDS Treatment Information Exchange (CATIE). For more information visit CATIE's Information Network at http://www.catie.ca

Source: CATIE: CANADIAN AIDS TREATMENT INFORMATION EXCHANGE


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