Rates at which HIV-positive people got admitted to the hospital because of AIDS fell sharply from 2001 through 2008 in a four-city U.S. study.1 But heart, kidney, and lung disease became more frequent causes of hospital admission in this group during the study period. Non-AIDS infections accounted for the largest proportion of hospital admissions during the study, and that rate did not change from 2001 through 2008.
Strong antiretroviral combinations greatly improved the health of HIV-positive people over the past 15 years. But people with HIV still get admitted to the hospital at higher rates than people without HIV. Ten years ago, a study by the HIV Research Network in the United States found that AIDS illnesses were the main cause of hospital admission, followed by digestive system and liver disease, psychiatric illness (like severe depression), and cardiovascular (heart) disease.2 Recently this same study group found an overall drop in the hospital admission rate from 35 to 27 admissions per 100 person-years in people with HIV from 2002 through 2007.3
Understanding why HIV-positive people are going to the hospital in the current antiretroviral treatment era could help healthcare providers focus on at-risk people to improve their health and prevent hospital admissions. To learn more about reasons for hospital admissions and changing admission rates in people with HIV, the HIV Research Network conducted a new study of people cared for from 2001 through 2008.1
The HIV Research Network includes 12 centers that care for HIV-positive adults in 11 U.S. cities. This analysis focused on 4 sites, 2 in the West, 1 in the South, and 1 in the Northeast. This study included all HIV Research Network participants at least 18 years old and in care at some point from 2001 through 2008.
The researchers defined years of active care as those years in which an HIV patient had at least 1 clinician visit and 1 CD4 count measurement. Each study participant stopped contributing data to the analysis if he or she fell out of active care.
The HIV Research Network team counted how many times each person went to the hospital during active care. The researchers then carefully determined the reason for each hospital admission. They used standard statistical methods to determine (1) whether each of the main reasons for hospital admission accounted for more or fewer hospital admissions from year to year and (2) factors that influenced each of the main reasons for hospital admission (like age and CD4 count).
The study included 11,645 people with HIV. Some people were in active care for just 1 year between 2001 and 2008. Others were in active care for 2 years, others for 3 years, and so on all the way through 8 years. The whole study group was in care for an average of 3 years.
In 2001, the first study year, 72% of study participants were men, 43% black, 39% white, and 15% Hispanic. Gay/bisexual men made up 40% of the study group in 2001 and 41% in 2008. People infected with HIV during male-and-female sex made up 26% of the study group in 2001 and 28% in 2008. People who got infected with HIV while injecting drugs made up 28% of the group in 2001 and 20% in 2008.
Median age of people in the study group was 40 in 2001. Median CD4 count when first measured in each person rose from 341 in 2001 to 416 in 2008. The percentage of people with a CD4 count above 350 rose from 49% in 2001 to 60% in 2008. The percentage of people with a viral load below 400 copies climbed from 35% in 2001 to 59% in 2008. These improvements in CD4 count and viral load during the study period probably mean (1) people were taking more effective antiretroviral combinations as the study progressed and (2) people were starting antiretroviral therapy at higher CD4 counts in more recent years.
During active care for HIV infection, 4423 people (38% of the 11,645-person study group) went to the hospital at least once. There were 13,323 hospital admissions during the study period. The rate of admission to the hospital for any cause fell from 37.1 per 100 personyears in 2001 to 28.9 per 100 person-years in 2008, an average incidence rate drop of 2% per year.
Non-AIDS infections (like bacterial pneumonia) caused the largest proportion of hospital admission (26.2%), followed by AIDS illnesses (15.3%), heart disease (7.5%), psychiatric illness such as severe depression (7.1%), digestive system and liver disease (7.1%), kidney, genital, and urinary system disease (5.2%), non-AIDS cancers (4.5%), lung disease (4.4%), and a cluster of diseases in volving the endocrine system, the immune system, metabolism, and nutrition (4.3%).
To calculate whether these illnesses caused more or fewer hospital admissions from one year to the next, the researchers used a statistical analysis that weighed the impact of age, race, CD4 count, viral load, and whether a person injected drugs. This analysis found the hospital admission rate for AIDS illnesses fell 6% yearly, while the admission rate rose 9% yearly for lung disease, 9% yearly for kidney disease, and 6% yearly for heart disease (Figure 1). However, throughout the study AIDS illnesses remained a more frequent cause of hospital admission than lung, kidney, or heart disease. Year-to-year hospital admission rates changed very little or not at all for non-AIDS infections, psychiatric illness, non-AIDS cancers, digestive system and liver disease, endocrine and immune diseases, and for any cause.
Figure 1. Among the major causes of hospital admission of HIV-positive people from 2001 through 2008, four changed significantly in how often they caused admissions over those years. The admission rate for AIDS illnesses fell 6% yearly, while the admission rates for lung, kidney, and heart disease rose.
* Yearly change was statistically adjusted to account for factors like age and race, as well as for clinical factors.
This statistical analysis also identified factors that raised hospital admission rates for any condition and for each of the major illnesses already discussed (Tables 1 and 2). Being 50 or older was linked to a higher hospital admission rate than being 35 or younger for every disease category except AIDS illnesses and psychiatric illness. Among people 50 or older, heart disease passed AIDS illness as the second most-frequent cause of hospital admission, after non-AIDS infection. A lower CD4 count raised chances of hospital admission for every major illness considered. African Americans, women, and injection drug users tended to have higher hospital admission rates for most of the major illnesses considered.
|Table 1. Factors that Independently Affect Risk of Hospital Admission in 5 Disease Categories|
|Reason for Hospital Admission (Incidence Rate Ratios)|
|All Causes||Non-AIDS Infection||AIDS Illness||Heart Disease||Psychiatric Illness|
|Age 36-49*||↑ 1.10x||--||--||↑ 2.01x||--|
|Age 50+*||↑ 1.44x||↑ 1.19x||--||↑ 5.01x||--|
|Female vs male||↑ 1.34x||↑ 1.20x||↑ 1.26x||↑ 1.33x||--|
|Black vs white||↑ 1.38x||↑ 1.35x||↑ 1.31x||↑ 1.76x||↑ 1.80x|
|Hispanic vs white||↑ 1.20x||--||↑ 1.57x||--||↓ 0.67x|
|IDU vs non-IDU||↑ 1.61x||↑ 1.75x||--||↑ 1.50x||↑ 2.83x|
|CD4 at or under 50†||↑ 4.83x||↑ 4.39x||↑ 34.8x||↑ 2.24x||↑ 2.05x|
|CD4 51-200†||↑ 2.53x||↑ 2.57x||↑ 10.3x||↑ 1.58x||↑ 1.78x|
|CD4 201-350†||↑ 1.45x||↑ 1.57x||↑ 3.06x||↑ 1.31x||--|
|VL 400-49,999‡||↑ 1.19x||↑ 1.51x||↑ 1.39x||↑ 1.23x||--|
|VL 50,000+ or missing‡||↑ 1.46x||↑ 2.03x||↑ 2.29x||↑ 1.34x||--|
* Compared with 18 to 35.
† Compared with over 350.
‡ Compared with under 400 copies.
CD4, CD4 count; IDU, injection drug user; VL, viral load.
An up arrow (↑) means increased risk. A down arrow (↓) means decreased risk. A dash (--) means no significant association between the risk factor and hospital admission.
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