Obese patients in US have poorer CD4 cell gains after starting HIV treatment

Obesity has a negative impact on CD4 cell gains after the initiation of HIV treatment, US investigators report in the on-line edition of AIDS.

Although obesity was protective of immune function in the period before potent antiretroviral therapy became available, the investigators found that obese individuals had significantly smaller gains in CD4 cell count after starting HIV treatment than both patients of normal weight and those who were overweight.

“Excessive weight (BMI above 30 kg/m²) was not beneficial in the HAART [highly active antiretroviral therapy] era and was associated with smaller CD4 cell count increases,” comment the researchers.

The prevalence of obesity is increasing amongst patients with HIV. Excessive weight has been associated with an increased risk of several severe health conditions. Some of these, such as diabetes, cardiovascular disease, and kidney dysfunction, are now significant causes of illness in those with HIV.

However, little is known about the impact of obesity on immune function.

Investigators from the US Military HIV Natural History Study therefore conducted a longitudinal study monitoring the relationship between weight and CD4 cell count in 1001 patients who seroconverted for HIV.

These individuals had their weight and CD4 cell count monitored on a twice-yearly basis. Weight was categorised using body mass index (BMI).

At the time of seroconversion, 1% of patients were underweight, 51% were of normal weight, 40% were overweight, and 8% were obese.

A total of 394 individuals were diagnosed before effective HIV treatment became available. Over a median of four years of follow-up, significantly smaller decreases in CD4 cell count were seen in obese patients (-50 cells/mm³) compared to underweight (-158 cells/mm³) and normal weight (-125 cells/mm³) patients.

Next, the investigators analysed the CD4 cell changes seen in the 607 patients who seroconverted after the introduction of potent HIV therapy.

Over a mean of four years of follow-up, CD4 cell counts fell by 1 cell/mm³ in patients who were underweight, but increased by an average of 103 cells/mm³ in individuals of normal weight and 116 cells/mm³ amongst those who were overweight.

The average gain in CD4 cell count for patients who were obese was significantly lower at 50 cells/mm³ (p = 0.01).

Changes in CD4 cell count after the initiation of antiretroviral therapy were then monitored.

Increases were seen in all weight categories. The lowest gain was for patients who were underweight (127 cells). Those who were of normal weight gaining an average of 210 cells/mm³, overweight patients gained an average of 230 cells/mm³, and obese patients gained an average of 188 cells/mm³.

Compared to patients who were overweight, those who were obese gained significantly fewer (p = 0.008) CD4 cells after starting therapy with anti-HIV drugs.

“Our study demonstrates that weight appears to affect CD4 cell counts over the course of HIV infection”, comment the investigators. “Although higher BMI categories were associated with less reduction in CD4 cell counts during the pre-HAART era, excess weight was not similarly beneficial during the HAART era … obesity may be associated with poorer immunologic recovery … in the setting of HAART availability.”

The researchers speculate the inflammatory effect of obesity could adversely affect immune function. In addition, levels of antiretroviral drugs may be lower in those who are obese.

“These data suggest that HIV providers should be cognizant of the potential negative effects of obesity … including the potential adverse effects on CD4 cell count,” conclude the investigators. “Weight monitoring and maintenance programs may be useful components of HIV clinical care visits.”