September 5, 2006 (AIDSmeds)—A report published in the August issue of The Journal of Clinical Endocrinology and Metabolismhas confirmed that HIV-positive women are more likely to suffer fromlow bone mineral density (BMD) compared to HIV-negative women. However,the study also suggests that the bone loss in HIV-positive women doesnot appear to significantly worsen over time and is often related totraditional risk factors, including low body weight and cigarettesmoking.

Osteoporosis and osteopeniaare familiar terms to many older adults. A diagnosis of osteoporosis, aserious loss of BMD, can bring on a lot of anxiety, as it generallymeans that a person's bones have become weaker and are more likely tobreak. And while a diagnosis of osteopenia, a less serious loss of BMD,does not mean the same thing as an osteoporosis diagnosis, it can be ofconcern just the same.

Previous studies have reportedincreased rates of osteopenia and osteoporosis among HIV-positivepeople. However, most of these studies were "cross sectional" in theirdesign, meaning that they relied on a one-time "snapshot" of allpatients enrolled and didn't follow patients to see if the problemworsened. What's more, the studies were generally too small to evaluatethe risk factors for decreased BMD in the HIV-positive volunteers.

Inthe newest study, conducted at Harvard Medical School in Boston,changes in BMD among 100 HIV-positive women – compared to 100HIV-negative women similar in age and race – were monitored over atwo-year follow-up period.

Dual energy X-rayabsorptiometry (DEXA) scans, used to measure BMD, were conducted in allof the study volunteers upon entry and every six months for a total of24 months.

At the start of the study, the HIV-positivewomen had significantly lower BMD at three important skeletallocations: the spine, the hip, and the femoral neck (the ball part ofthe hip joint). The differences between the two groups werestatistically significant, meaning that the differences in BMD betweento two groups weren't likely due to chance.

Approximately41% of the HIV-positive women had osteopenia and 7% had osteoporosis.Oddly, the paper did not summarize rates of osteopenia or osteoporosisin the HIV-negative women for comparison purposes.

Whilethe differences between the HIV-positive and HIV-negative womenpersisted for two years, BMD actually remained stable in both groups ofwomen. This stability, the Harvard group pointed out, argues againstworsening bone loss in HIV-positive women compared to HIV-negativecontrols.

Blood markers of bone metabolism – notablyosteocalcin and N-telopeptide of type 1 collagen – were higher inHIV-positive women compared to HIV-negative women.

Bonemetabolism is better known as "remodeling," with two important types ofbone cells to be familiar with: osteoclasts and osteoblasts.Osteoclasts are responsible for removing old or worn bone, which canleave cavities (lacunas). The removal of bone, and the creation oflacunas, is known as bone resorption. It is the job of the osteoblaststo fill these lacunas with new collagen and mineral, a process known asbone formation.

Just as healthy bone structure requiresadequate amounts of collagen and mineral, there must also be a healthybalance of bone resorption and formation. If the amount of new bonedeposited by osteoblasts equals the amount of bone taken away byosteoclasts, the bones stay strong. However, the Harvard researchsuggests that the bone resorption and formation seems to prematurelyshift in HIV-positive women, resulting in more bone being taken awaythan deposited.

Many of the risk factors for low BMDwere not directly related to HIV, including low body weight, smokinghistory, low vitamin D levels, and high levels of bone metabolismmarkers. However, the longer women had been infected with HIV or hadbeen treated with at least one nucleoside reverse transcriptase inhibitor (NRTI), the greater the association with decreased BMD.

Basedon these findings, the study authors concluded that HIV-positive womenwith easy-to-document risk factors for bone loss, including low bodyweight and blood markers of bone metabolism, should be screened forbone loss with DEXA scanning.