CROI 2016: Life Expectancy of HIV-Positive People in U.S. Still Lags 13 Years Behind HIV-Negatives

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A study presented at the Conference on Retroviruses and Opportunistic Infections (CROI 2016) comparing life expectancies of HIV-positive and HIV-negative people within the Kaiser Permanente health system has found that although life expectancy among HIV-positive people has improved, expected life at age 20 remains 13 years behind that of matched HIV-negative people. This 13-year gap did not improve between 2008 and 2011, the last year of follow-up in this cohort study.

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The study was also able to compare life expectancies for both HIV-positive and HIV-negative people in the Kaiser system with life expectancies in the U.S. general population. Life expectancy is 2 years lower in the U.S. general population than in the HIV-negative group at Kaiser, and the difference is greater in some groups, notably 5 years in men. At least part of this difference will be due to HIV, though part will also be due to differences in health coverage.

The researchers also looked at risk factors for mortality and were able to calculate life expectancy if these were absent. Starting antiretroviral therapy (ART) early, not having hepatitis B or C, and not having a history of drug and alcohol problems all raised life expectancy, but the biggest difference was due to smoking. Nonetheless, even HIV-positive people who had never smoked had a life expectancy over 5 years lower than HIV-negative people.

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The study looked at mortality rates among 24,768 HIV-positive people within the Kaiser Permanente system and compared them against 10 times that number of HIV-negative people (257,600) also in the system between the years 1996 and 2011. The 2 groups were matched for age (31 at entry to the study) and sex (91% male). Deaths were ascertained from death certificates and social security records so they could be traced even if people left the Kaiser system.

Study subjects were matched approximately for ethnicity: 56% of HIV-positive and 44% of HIV-negative people were white, 21% versus 25% were black, and 18% versus 10% were Hispanic. Race/ethnicity was less well-recorded in HIV-negative people.

Nearly half (45%) of the HIV-positive people had ever smoked versus 31% of the HIV-negatives, 21% of positive versus 9% of negative had ever had drug or alcohol problems, and 12% versus 2% had ever had hepatitis B or C.

In the HIV-positive group, 75% were men who acquired HIV through sex with other men, 16% were heterosexual men and women, 7% got HIV through injection drug use, and 2% through other routes such as occupational exposure.

There were 46% who were already on ART when they joined the Kaiser cohort, while another 40% started during their period in the study. One-third (35%) did not start ART until their CD4 count was below 200 cells/mm3, while 18% started at CD4 counts over 500 cells/mm3.

The cohort study starts at 1996, which was just before effective combination ART became generally available, so there was a rapid decrease in mortality among HIV-positive people in the first 2 years of the study; it then continued to decline at a slower rate from 1998 onwards. In 1996-1997 the death rate among HIV-positive people was 7.08% per year. By 2011 this had declined to 1.05% per year. The equivalent rates for HIV negative people were 0.44% per year in 1996-1997 and 0.38% per year in 2011.

What did this do to life expectancy? In 1996-1997 the life expectancy at age 20 of an HIV-positive person was 19 years -- in other words, they could only expect to live, on average, in the absence of any improvement in treatment, until they were 39. By 2011, this had improved to 53 years, i.e., death on average at age 73.

This, as it happens, was the life expectancy at age 20 of HIV-negative people in 1996-1997; by 2011 this had improved to 65 years, i.e., death on average at age 85.

Among HIV-positive women, life expectancy improved slightly less than it did for men. For subgroups, instead of contrasting 1996-1997 with 2011, the researchers contrasted life expectancy during the whole period between 1996 and 2007 with life expectancy during 2008-2011.

For HIV-positive men, life expectancy at age 20 was 37 more years in the 1996-2007 period and 51 years in 2008-2011; for women it was 38 years in 1996-2007 and 49 years in 2008-2011.

The increase in life expectancy among white people was the same as it was in men. For black people it was lower during both periods and did not improve as much as it did for white people (38 years at age 20 in 1997-2007 and 46 in 1998-2001 -- this was pretty much the same increase as seen in people who inject drugs). Hispanic people did rather better, with an improvement from 39 to 52 years. Among gay men, life expectancy improved from 40 to 51 years.

One interesting aspect of this study is that death rates and life expectancy among HIV-positive people has tended to be compared with the general population's figures. But of course people with HIV form part of the general population. Thus, taken over the whole study period, life expectancy for HIV-positive people at age 20 was 49 years, for HIV-negative people it was 62 years, and in the U.S. general population it was 60 years. This means that if the Kaiser HIV-negative population resembles the HIV-negative U.S. general population, then HIV reduces life expectancy in the general population by 2 years.

In subgroups, the difference was bigger: for men the gap between HIV-negative and general-population life expectancy was 5 years, in black people 3 years, and in Hispanic people 6 years. However, Kaiser’s members are not likely to resemble the general population, so the actual reduction in life expectancy due to HIV in the general population is likely to be lower than this.

There still remains a gap of 13.1 years between HIV-positive and HIV-negative life expectancy in this study, and this did not improve between 2008 and 2011.

The researchers then looked at factors that might narrow this gap. Among people who started ART at CD4 counts over 500 cells/mm3, the life expectancy gap between them and HIV-negative people was 7.9 years, i.e., early treatment added 5.2 years to an HIV-positive person’s life expectancy. Not having had hepatitis B or C added 5.9 years, not having had problems with drugs or alcohol added 6.5 years, and not having ever smoked added 7.7 years. This still left a life expectancy gap of 5.4 years, however.

Presenter Julia Marcus of Kaiser commented: "In addition to timely ART initiation, risk-reduction strategies such as smoking cessation may further narrow the survival gap." She said they would consider looking at other factors that might impact life expectancy such as depression, which is more common in people with HIV.

"Future studies should determine if this survival gap persists in more recent years, and if so, identify factors that may contribute," she added.

3/1/16

Reference

JL Marcus, C Chao, W Leyden, et al. Narrowing the Gap in Life Expectancy for HIV+ Compared With HIV- Individuals. Conference on Retroviruses and Opportunistic Infections. Boston, February 22-25, 2016. Abstract 54.