Women who are overweight or obese experience slower HIV progression and have higher CD4 cell counts than women who are under weight, according to US research published in the supplement to the September 1st edition of Clinical Infectious Diseases.
Several earlier studies have found a relationship between weight and HIV disease progression. Investigators involved in the HIV Epidemiology Research (HER) Study recruited 799 HIV-positive women to establish if there was an association between body mass index (BMI) and several clinically important HIV disease outcomes (time to first CD4 cell count below 200 cells/mm3, first CD4 cell count below 100 cells/mm3, first opportunistic infection, and death). The American researchers also wished to see if CD4 cell count and BMI were related over time.
All the women included in the study were AIDS-free at baseline and had a CD4 cell count above 200 cells/mm3. The women were divided into one of four mutually exclusive groups on the basis of their BMI (underweight, normal weight, over-weight and obese). The median baseline BMI was 24.6kg/m2 and the median BMI for the four groups was 18.5, 22.5, 26.9 and 33.6kg/m2 respectively. Overweight and obese women were less likely to be injecting drug users (obese 41% versus, 51% overweight, and 56.9% underweight). Income level was comparable across all BMI groups at between $501 and $1,000 per month. None of the women were taking HAART at baseline, and the mean duration of diagnosed HIV infection was approximately three years across all BMI categories.
Investigators established that a higher baseline BMI was associated with a delay in the time taken for the CD4 cell count to fall below 200 cells/mm3. In particular, the investigators found that women with a BMI below 20 were more likely to see their CD4 cell count fall below 200 cells/mm3 than obese women with a BMI above 30 (adjusted hazard ratio 1.59, 95% CI, 0.97 – 2.58). Odds ratios also indicated to the investigators that women with higher BMI were less likely to experience HIV-related events, “whether clinical, immunological, or mortality related.”
The investigators highlighted their findings regarding mortality, emphasising that women who were underweight had an odds of death 3.1 times greater than obese women. In addition, the risk of having a CD4 cell count below 100 cells/mm3 was two times greater for women in all categories compared to obese women.
A relationship between CD4 cell count and BMI was also established.. Women whose BMI was higher had consistently higher CD4 cell counts over twelve clinic visits. The difference was most pronounced between women who were underweight and had a BMI below 20, whose median CD4 cell count fell from approximately 250 cells/mm3 at visit one to 250 cells/mm3 at visit twelve, and obese women whose median CD4 cell count was consistently between 400 and 450 cells/mm3. In addition, investigators also found that increases in BMI were associated with slight increases in CD4 cell count (1.65 cells/mm3 per unit change in BMI), even after controlling for earlier CD4 cell counts, viral load and anti-HIV therapy.
The investigators comment, “women with a baseline BMI 25. Even among the women who entered the cohort with an undetectable baseline viral load or with a baseline CD4 cell count >500 cells/mm3, those who were overweight or obese had higher CD4 cell counts. Regression analysis showed an association between BMI and a risk of HIV progression, whether immunological, clinical, or mortality related.”
Interestingly, the investigators note that the excess weight carried by the women with higher BMI in their cohort was likely to consist of fat, rather than lean muscle mass. They also observe that this finding is consistent with an earlier study which found a protective association between fat mass and HIV progression, particularly decline in CD4 cell count, even when controlling for viral load, use of HAART, and known duration of HIV infection.
However, the HERS researchers emphasise that their finding should be viewed with caution, and admit that it is possible that women with lower CD4 cell counts are at greater risk of weight loss. Nevertheless, they believe that their research suggests that there is a protective effect of obesity, and suggest a role for the hormone leptin, which fat cells are a principal source of.
Although overweight and obese women were less likely to be injecting drug users, HIV risk activity (injecting drugs versus high-risk sexual contact) was not a significant predictor of outcome. Indeed, an earlier study of this cohort did not find a significant association between injecting drug use, loss of CD4 cells, or HIV related mortality.
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Jones CY et al. Overweight and HIV progression in women: associations HIV disease progression and changes in body mass index in women in the HIV Epidemiology Research Cohort. Clinical Infectious Diseases 37 (Suppl.2), S69 – 80, 2003.