November 8, 2013
Having HIV is not independently associated with arterial stiffness -- a trait linked to cardiovascular disease risk -- despite HIV-infected individuals having a modest, but clinically significant, increase in arterial stiffness when compared to their uninfected counterparts. Instead, factors such as smoking and hypertension may account for the increase, according to study results presented at EACS 2013 in Brussels, Belgium.
To provide some background, HIV infection has been associated with an increased risk of cardiovascular disease and one of the markers for this condition is arterial stiffness, which is measured by pulse wave velocity (PWV), or how fast blood moves through the circulatory system. With age, or other changes to the arterial wall, blood vessels become stiffer and blood moves faster through the system, giving the heart less time to rest. PWV is directly dependent on mean arterial pressure (MAP) and past research has shown that an increase of 1 m/s (meter per second) in PWV is associated with a 14% greater incidence in total cardiovascular events.
However, studies measuring PWV in HIV-infected patients have been small and their results inconsistent. So, researchers led by Katherine Kooij, M.D., compared PWV in a cohort of HIV-infected and HIV-uninfected people to determine if there is an independent association between HIV and PWV, as well as possible determinants of PWV.
The study included 566 HIV-infected and 511 HIV-uninfected individuals, all 45 or older. Both groups had comparable median ages (52.8 versus 52), gender distribution (89.1% men versus 86% men) and proportion of men who have sex with men (76.4% versus 71.4%). However, the HIV-infected group included more current smokers (32.9% versus 24.8%) and users of antihypertensive drugs (31.3% versus 22.4%). The HIV-infected participants also displayed higher levels of inflammation and immune activation markers, such as hs-CRP and sCD163.
The researchers performed three measurements of PWV, as well as systolic and diastolic blood pressure, using an Arteriograph system, which registers oscillometric pressure waves in the aorta through an upper arm cuff. Additional information on potential determinants of arterial stiffness was collected with laboratory measurements and questionnaires. The data underwent a statistical analysis with multivariable linear regression models using PWV as a dependent variable, adjusted for MAP.
The analysis revealed a slightly higher, but significant unadjusted PWV in HIV-infected individuals than in HIV-uninfected individuals (7.9 m/s versus 7.7 m/s, P = .004). When these results were adjusted for MAP and gender, the difference between the two remained at 0.19 m/s (P = .04). If compared to a PWV increase due to age (+0.29 m/s per 5 years older, P < .001), having a positive HIV status would be the equivalent of being 3 to 3.5 years older.
However, when the PWV values were adjusted for other factors, such as smoking and use of antihypertensive drugs, HIV-infected status was no longer independently associated with arterial stiffness. In this setting, the difference between HIV-infected and HIV-uninfected PWV was only 0.022 m/s (P = .8). In contrast, every 5 pack-years (smoking 20 cigarettes a day per year, about 7,305 cigarettes) for current smokers accounted for a difference of 0.121 m/s (P < .001), while use of antihypertensive drugs represented an increase of 0.527 m/s (P < .001). The researchers also found that the inflammation marker hs-CRP and the monocyte activation marker sCD163 were associated with a higher PWV: 0.039 m/s (P = .001) and 0.056 m/s (P = .04), respectively. But sCD163 was only a significant determinant in men.
According to the researchers, the small, but significant, difference in arterial stiffness and PWV between middle-aged HIV-uninfected and HIV-infected individuals can be explained by a higher prevalence of factors such as hypertension and smoking, as well as increased markers of inflammation and monocyte activation. While HIV itself is not independently associated with greater arterial stiffness, Kooij and her team conclude that the higher PWV value in the HIV-infected group may indicate a greater vascular age in this population, which warrants a closer look, since it may become more important as people living with HIV get older.
Fred Furtado is a science writer based in Rio de Janeiro, Brazil.
Follow Fred on Twitter: @Patchlord.