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Resting Metabolic Rate Higher in Older Men With Than Without HIV
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7th International Workshop on HIV and Aging, September 26-27, 2016, Washington, DC
Mark Mascolini
Resting metabolic rate--a mortality marker--proved higher in older US men with HIV infection than in a comparison group of men without HIV [1]. The HIV-positive men had a higher resting metabolic rate despite good control of their HIV infection.
Johns Hopkins and National Institute of Aging researchers who conducted this study explained that resting metabolic rate--sometimes called the energetic cost of living--slows as people age, mainly because of changing body composition. This slowing is not as fast in people with chronic conditions, and attenuated slowing may signal a higher death risk. People with uncontrolled HIV infection have a higher than normal resting metabolic rate, the researchers noted. They conducted this study to assess the impact of controlled HIV infection on the association between resting metabolic rate and aging.
The analysis involved HIV-positive and negative men older than 39 in the Baltimore group of the Multicenter AIDS Cohort Study (MACS), an ongoing comparison of HIV-positive men who have sex with men (MSM) and MSM at risk of HIV infection. The researchers assessed resting metabolic rate cross-sectionally in 2015 and 2016 by indirect calorimetry. They explored the association between HIV status and resting metabolic rate in a linear regression model adjusted for age, body mass index, and DXA-measured percent body fat.
The 40 HIV-positive men were significantly younger than 35 HIV-negative men--average 58.5 versus 64.5 years (P < 0.01)--and included a significantly higher proportion of blacks (57.5% versus 22.9% (P < 0.01). There was a trend to lower extremity fat in the men with HIV (11.6 versus 13.3 kg, P = 0.18), and men with HIV had significantly lower estimated glomerular filtration rate (eGFR, 79.7 versus 90.3 mL/min, P = 0.04). Most men with HIV, 93%, had an undetectable viral load.
In an unadjusted analysis, resting metabolic rate was nonsignificantly higher in the HIV group (1748 versus 1668 kcal/day, P = 0.20). Multivariable regression analysis determined that HIV was associated with a 66 kcal/day higher resting metabolic rate, but that association fell short of statistical significance (P = 0.17).
When the researchers eliminated age from the model, HIV was significantly associated with an 86.7 kcal/day higher resting metabolic rate (P = 0.05). Other variables independently linked to higher resting metabolic rate in this model were lean mass (coefficient 17.1, P < 0.01), fat mass (coefficient 5.9, P = 0.04), diabetes (coefficient 117.7, P = 0.04), and eGFR (coefficient 2.4, P = 0.02). The Hopkins team calculated that a nondiabetic 60-year-old HIV-positive man with the same lean mass, fat mass, and eGFR as a nondiabetic 60-year-old HIV-negative man would have a 187 kcal/day higher resting metabolic rate.
The researchers concluded that "HIV appears to attenuate the age-related decline in resting metabolic rate" and that metabolic comorbidities like diabetes and impaired kidney function exacerbate that HIV effect. The researchers suggested that the higher resting metabolic rate in virologically suppressed men with HIV than in HIV-negative men "may be a compensation for the residual inflammation and greater comorbidity burden" in aging men with HIV.
Reference
1. Schrack J, Brown T, Ferrucci L, Margolick J. HIV infection attenuates the age associated slowing of resting metabolic rate. 7th International Workshop on HIV and Aging, September 26-27, 2016, Washington, DC. Abstract 2.
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