Wednesday October 12 2011
The HIV virus causes the body's defences to decline
“More Britons than ever have HIV – but their life expectancy after diagnosis has never been higher,” The Independent has today reported. The newspaper said new research has shown that the life expectancy of UK HIV patients had improved by 16 years in the past decade.
The news is based on a study that looked at data on over 17,000 adults with HIV who were treated with antiretroviral drugs, which have now become a standard treatment for slowing the progress of the virus. By analysing data on deaths among this population, researchers estimated that antiretroviral users aged 20 in 1996 would be expected to live to an average age of 50 but that by 2008, this group were expected to live to an average age of almost 66.
The researchers also found that life expectancy was greater in people who started their antiretroviral treatment at around the recommended stage of their disease, rather than once the disease became more advanced.
There are some points to consider when looking at these results. In particular, the fact that the life expectancies calculated are projections that will need to be confirmed by longer-term follow-up. Also, the methods used did not allow the researchers to take into account other factors that could influence results, such as lifestyle factors, which could lead to increased death from non-HIV causes. However, it does seem likely that improvements in antiretroviral treatment are responsible for at least some of this improvement in life expectancy.
Overall, these results are encouraging and emphasise the improvements in treatments seen in recent years. However, the life expectancies among people with HIV are still projected to be lower than people among the general population. This highlights the need to further improve both treatment and earlier diagnosis of the condition, which would allow antiretrovirals to be given sooner and help reduce transmission of the virus.
Where did the story come from?
The study was carried out by researchers from various medical and academic institutions in the UK, including universities, HIV services and departments, hospitals and NHS Trusts. It was funded by the UK Medical Research Council and published in the peer-reviewed British Medical Journal.
This research was covered by BBC News and The Independent, and both provided balanced coverage. The Independent also included information about HIV gathered from other UK sources. It published a short feature article explaining one man’s account of living with HIV, which may provide readers with an understanding of how treatment of the condition has advanced.
What kind of research was this?
This research presented results from an ongoing cohort study called the UK Collaborative HIV Cohort study, which began in 2001. This particular study looked at the life expectancy of people aged 20 years and above who are being treated for HIV. It also looked at how earlier and later treatment of their disease affected their life expectancy.
Life expectancy and mortality were compared to rates in the general population using publically available data on deaths between 1996 and 2006.
HIV is a type of virus called a retrovirus, and the drugs used to treat HIV infection are called antiretrovirals. Antiretroviral drugs have been shown to be beneficial in the treatment of HIV and have become standard care, meaning it would not be ethical to carry out randomised controlled trials where some individuals were not offered these drugs. Therefore, cohort studies are the best feasible way to look at their effects on life expectancy.
However, as with all cohort studies, it is possible that different groups of people being compared may differ in factors other than the factor of interest (for example how advanced a person’s disease was when they started antiretrovirals), and this may influence any differences in outcomes seen.
What did the research involve?
The researchers gathered anonymised data on 17,661 adults aged 20 and over who had HIV and had started antiretroviral treatment in the UK between 1996 and 2008. To be eligible for inclusion into the study, the antiretroviral treatment a participant was using had to include at least three drugs, as three-drug regimens are better than two- or one-drug regimens.
The analysis excluded patients whose records were missing important information such as their age, sex or ethnicity. The researchers also excluded people who, it was assumed, caught HIV through injecting drug use, as they are reported to have a worse outlook than other groups.
HIV infects and kills a particular type of white blood cell called the CD4 cell. This reduces the body’s ability to cope with infection. The number of CD4 cells a person has is a measure of how severe their HIV is, with fewer CD4 cells indicating more advanced disease. For this study, the researchers excluded people who had more than 350 CD4 cells in each microlitre of their blood. The authors report that current UK guidelines recommend that in most cases antiretroviral treatment should be started in symptom-free people with HIV once their CD4 count drops below this level (350 or fewer CD4 cells per microlitre).
The researchers identified those people who died (from any cause) and verified their age at death using clinic records and national data on deaths. Using standard methods they analysed this data to calculate the average life expectancy past the age of 20 seen in the different time periods of the study. Further to this they assessed:
- Whether life expectancy had changed over the course of the study period.
- The life expectancies of women and men with HIV, and how these compared with life expectancy among the general population.
- Whether life expectancy differed in people who started antiretroviral treatment at different stages in their disease, as assessed using their CD4 counts. This particular analysis only included people who started treatment after 2000, as these people were more likely to be representative of what happens in current clinical practice; for example, using the same drugs currently being used to treat patients.
What were the basic results?
During an average of about five years of follow-up, 1,248 (7%) out of the 17,661 patients died. There were differences in the participants across the different time periods. For example, those starting antiretroviral treatment in 1996-1999 generally had more advanced disease than those starting treatment in later years. Those starting treatment in this period were also more likely to be white, male and to be men who have sex with men.
Life expectancy in adults with HIV being treated with antiretroviral drugs increased between 1996 and 2008:
- between 1996 and 1999 an individual aged 20 could expect to live on average another 30 years, to an average age of 50
- between 2006 and 2008 an individual aged 20 could expect to live on average another 45.8 years, to an average age of 65.8 years
The average life expectancy of a person with HIV being treated with antiretrovirals was still shorter than that of a similarly aged person in the general population. Between 1996 and 2006, the average life expectancy of a man aged 20 with HIV treated with antiretrovirals would be another 39.5 years (to age 59.5 years), while the average life expectancy of a man aged 20 in the general population would be another 57.8 years (to age 77.8 years).
Between 1996 and 2006, the average life expectancy of a woman aged 20 with HIV treated with antiretrovirals would be another 50.2 years (to age 70.2 years), and average life expectancy of a woman aged 20 in the general population would be another 61.6 years (to age 81.6 years).
The later on in their disease people started antiretroviral treatment, the lower their life expectancy. For a person aged 20 starting antiretrovirals:
- a CD4 count of less than 100 per microlitre was associated with an average life expectancy of an additional 37.9 years (to age 57.9 years)
- a CD4 count of 100-199 per microlitre was associated with an average life expectancy of an additional 41.0 years (to age 61.0 years)
- a CD4 count of 200-350 per microlitre was associated with an average life expectancy of an additional 53.4 years (to age 73.4 years)
Ethnicity did not appear to affect the results.
How did the researchers interpret the results?
The researchers conclude that life expectancy for people treated for HIV infection increased by over 15 years between 1996 and 2008, but is still about 13 years less than the general population. However, they predict ‘we should expect further improvements for patients starting antiretroviral therapy now with improved modern drugs and new guidelines recommending earlier treatment’.
This cohort study has found that life expectancy for adults with HIV treated with antiretrovirals has improved over the past 15 years in the UK. This is an encouraging finding. The research also found that those who start antiretroviral treatment when they reach the recommended stage (when their CD4 count is 200-350 per microlitre), have a life expectancy about 15 years longer than those who start much later (once their CD4 count is below 100 per microlitre). This supports the need to start soon after the recommended CD4 level is reached.
There are some points to note:
- The study compared life expectancy in different time periods and in people starting antiretrovirals at different stages of their disease. As many factors change over time, and the groups who started antiretrovirals at different stages may differ with regards to other factors, the differences in life expectancy seen may not entirely be due to the factor of interest (antiretroviral use). For example, the researchers were unable to take into account differences in lifestyle.
- Differences in smoking or socioeconomic status might have led to increased death from other causes in those with HIV. However, it seems likely that antiretrovirals would be responsible for at least some of the difference.
- The researchers suggest that the improvement in life expectancy seen over time is likely to be due to a number of factors. These include a larger proportion of individuals having less advanced disease; improvements in antiretroviral treatment; changes in populations demographics (including an increase in the number of women with the disease), and general increases in life expectancy in the population as a whole.
- The researchers note that some deaths may have been missed, but they tried to minimise this by checking for information on deaths from multiple different sources.
- Although the study used accepted methods to calculate life expectancy, most of the people in the study (93%) had not yet died, so these figures should be interpreted as predictions. Longer-term follow-up can determine how accurate these estimations were.
- The results do not apply to those who contract HIV through injecting drug use, as these individuals were not included in the study. They also do not apply to those not treated with antiretrovirals.
These results will be seen as important in highlighting not only the improvements in care and life expectancy of people with HIV that have been achieved in recent years, but also the benefits seen with early testing and treatment for HIV. More than a quarter of people living with HIV in the UK are unaware that they are infected. Earlier testing is not only important in terms of allowing earlier, possibly more effective, treatment, but also a necessary step for reducing further transmission.