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The latest forecasts of life expectancy in people with HIV in the UK, based on mortality data from the UK Collaborative HIV Cohort (UK CHIC) study, show that the average life expectancy of people on antiretroviral therapy (ART) with a CD4 count over 350 cells/mm³ is now very close to the national average, the eleventh International Congress on Drug Therapy in HIV Infection heard last week.

The UK CHIC study also found that life expectancy, which lags behind the average in younger people, approaches normal as people age. There is starting to be some evidence, though based on very small numbers of patient records, that if people with HIV in the UK reach the age of 60, their life expectancy may actually be starting to exceed the average, possibly because of superior medical monitoring and treatment for people with HIV compared to other older people.

Life expectancy is a projection into the future of how much longer people can expect to live, if current medical monitoring and treatment remains unchanged and if nothing unexpected happens. Up till now, because both HIV treatment and people’s health in general have been improving, life expectancy has been increasing.

However another study from Australia, based on current rates of treatment failure in people with HIV, warns that if antiretroviral therapy (ART) regimen failure continues at the current rate, people with HIV could run out of treatment options in later life. This would result in lower-than-expected life expectancies and higher mortality as people with HIV age unless the average time people achieve viral suppression on ART increases.

The UK Collaborative HIV Cohort (UK CHIC) is a database of 43,000 patient records from 20 of the largest HIV clinics in the UK. Margaret May of UK CHIC looked at the latest mortality data in people who started ART over the age of 20 between the years 2000 and 2008, and followed what happened to them till 2010. ‘Mortality’ means deaths for any reason, and the UK CHIC data exclude people whose risk factor for HIV was injecting drugs, though in the UK this is a small proportion of the HIV-positive population.

The study took the CD4 count and viral load immediately preceding people’s first taking ART and then took the last CD4 count and viral load for every following year. Results were expressed, in this study, as the additional number of years someone could expect to live on their 35th birthday.

People with an undetectable viral load who achieved a CD4 count of 350 cells/mm³ or over within a year of starting ART were forecast to have normal life expectancies.

After five years on ART, a male patient with a CD4 count of 350 to 500 cells/mm³ would have a life expectancy of 42 more years, or an expected lifespan of 77 years (81 if he had a CD4 count over 500 cells/mm³), and a female patient 46 more years or expected lifespan of 81 years (86 if she had a CD4 count over 500 cells/mm³). This compares with an expected lifespan at age 35 in 2012 of 80.1 for men and 88.6 for women in the UK population in general. The differences in life expectancy between people with CD4 counts over 500 cells/mm³ and people with count of 350-500 cells/mm³ were not statistically signficant.

Failure to achieve viral suppression took 11 years off life expectancy (equivalent to smoking over 40 cigarettes a day) and starting with a CD4 count under 200 cells/mm³ and achieving one over 500 cells/mm³ five years later added 11 years. Conversely, people who still had a CD4 count under 200 cells/mm³ after five years on ART had a life expectancy of 20 more years (24 years shorter than the average UK CHIC patient) implying, on average, that this group would die at age 55.

Statistician Caroline Sabin reviewed recent life expectancy data, including previous UK CHIC data. She emphasised that factors like late diagnosis, injecting drug use, and co-infection with hepatitis B and C, all tended to depress life expectancy in people with HIV. This meant that crude comparisons between life expectancy in the HIV-positive population and the HIV-negative population consistently reported lower life expectancies for people with HIV: in the case of the UK, by twelve to 13 years and more in countries like the US with more unequal access to healthcare.

However injecting drug use could reduce life expectancy by ten years, hepatitis C contributed 31.5% of the mortality seen in people with HIV, and although over a lifetime the impact of late diagnosis was limited, mortality in the first year after diagnosis was hugely greater than it is in any subsequent year. For instance the likelihood that someone diagnosed with a CD4 count of 140 cells/mm³ at age 30 would be dead by the age of 50 was about 25% but for someone diagnosed with a CD4 count of 430 cells/mm³ was about 10%.

What this means is that survival in itself adds a greater boost to life expectancy in people with HIV as they age than the general population, and Sabin uncovered some interesting statistics that showed that life expectancy in older people with HIV – over 60 – might actually be starting to exceed that in the general population, at least in men. HIV-positive heterosexual men in another cohort, the European COHERE collaboration, who had never had an AIDS-defining condition, had a lower death rate at age 60 than comparable men in the general population, possibly due to better medical monitoring and treatment.

Life expectancy calculations depend on nothing unexpected happening in the future. While unexpected occurrences such as new medicines could increase life expectancies, events such as a new disease, drug resistance or economic or natural disasters could also reduce life expectancies.

Researchers from the University of New South Wales in Australia warned that one unexpected event could be that, at current rates of treatment failure and without new classes of drug being discovered, people may run out of HIV treatment options within 43 years – that is, at age 78 if starting ART at age 35, but at age 62 if starting at 20, or mid-40s if starting as a baby. Furthermore this was only an average and 10% of patients could expect to run out of options within 28 years.

Antiretroviral therapy has made a huge difference to the lifespans of people with HIV: if there was no ART at all, the Australian researchers calculated that half of a group of people diagnosed with HIV at age 20 would be dead by the age of 28. If they took ART and did not run out of options, then they would expect to live till 82 – the same as the average Australian. But if drug resistance continued to accumulate at current rates, then average lifespan might be reduced to about 65.

Improvements in life expectancy were therefore crucially dependent on good adherence and on tolerable and convenient regimens, as well as good diagnosis and monitoring.

May M et al. Life expectancy of HIV-1-positive individuals approaches normal, conditional on response to antiretroviral therapy: UK collaborative HIV cohort study. Eleventh International Congress on Drug Therapy in HIV Infection, Glasgow, abstract O133, 2012. See abstract here.

Sabin C Review of life expectancy in people with HIV in settings with optimal ART access: what we know and what we don’t. Eleventh International Congress on Drug Therapy in HIV Infection, Glasgow, abstract O131, 2012. See abstract here.

Jansson J et al. Currently available medications might not be sufficient for lifelong treatment of HIV. Eleventh International Congress on Drug Therapy in HIV Infection, Glasgow, abstract O132, 2012. See abstract here.