Rate of Hospital Admissions for AIDS Falls, While Heart Disease Rate Climbs

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

How the Study Worked

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).

What the Study Found

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.

Yearly Change in Hospital Admission Rate by Disease Category From 2001 Through 2008
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 CausesNon-AIDS InfectionAIDS IllnessHeart DiseasePsychiatric 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.

Table 2. Factors That Independently Affect Risk of Hospital Admission in 5 Disease Categories
Reason for Hospital Admission (Incidence Rate Ratios)
 Digestive/Liver DiseaseKidney/GenitourinaryNon-AIDS CancerLung DiseaseEndocrine/Immune
Age 36-49*--↑ 1.44x↑ 2.20x↑ 1.87x↑ 1.55x
Age 50+*↑ 1.58x↑ 2.16x↑ 3.86x↑ 3.00x↑ 2.38x
Female vs male--↑ 1.31x--↑ 2.01x↑ 1.41x
Black vs white--↑ 3.45x----↑ 2.01x
Hispanic vs white↑ 1.50x--------
IDU vs non-IDU↑ 1.62x↑ 1.82x--↑ 2.37x↑ 1.34x
CD4 at or under 50↑ 2.73x↑ 4.77x↑ 2.55x↑ 4.21x↑ 5.87x
CD4 51-200↑ 2.76x↑ 2.66x↑ 2.96x↑ 3.05x↑ 3.13x
CD4 201-350--↑ 1.39x↑ 1.66x↑ 1.88x↑ 1.44x
VL 400-49,999----------
VL 50,000+ or missing----------

* Compared with 18 to 35.

† Compared with over 350.

‡ Compared with under 400 copies.

¶ Includes endocrine, nutritional, metabolic, and immune diseases.

CD4, CD4 count; IDU, injection drug user; VL, viral load.

An up arrow (↑) means increased risk. A dash (--) means no significant association between the risk factor and hospital admission.

People admitted to the hospital with an AIDS illness had the longest hospital stays, averaging 10.5 days, followed by lung disease (8.3 days), psychiatric illness (7.9 days), non-AIDS cancers (7.7 days), and non-AIDS infections (7.3 days).

What the Results Mean for You

This large study of U.S. adults with HIV made several important findings about hospital admission rates and reasons for hospital admission.

First, AIDS illnesses caused fewer hospital admissions over the 2001-2008 study period. AIDS caused 18% of all admissions in 2001 and 8% in 2008. This drop reflects the improving CD4 counts and falling viral loads in the study group, which probably result from easier-to-take and stronger antiretroviral combinations. Also, people were probably starting antiretroviral therapy at higher CD4 counts and so spending less time with a dangerously low CD4 count. Still, AIDS remained a relatively frequent cause of hospital admission.

Second, non-AIDS infections like bacterial pneumonia caused most hospital admissions throughout the study period. From 2001 through 2008, researchers found no decline in the rate at which people went to the hospital with a non-AIDS infection. Preventing these infections remains a highly important part of HIV care. Factors that raise the risk of bacterial pneumonia include older age, lower CD4 count, smoking, other lung diseases, and heart disease.4

Third, the rates at which heart, kidney, and lung disease caused hospital admissions rose over the study period. The researchers say more work is needed to examine these results, because some other studies of people with HIV did not make similar findings. A large study in Denmark did find a rising rate of hospital admissions for heart disease for 1995 through 2007.5 At the same time, many studies show that heart, kidney, and lung disease are serious threats to people with HIV, even if they do not always send people to the hospital. HIV-positive people should take steps to avoid these diseases by quitting smoking, avoiding obesity, and exercising.

In people with and without HIV, older age raises the risk of hospital admission. By weighing the impact of other factors that increase chances of hospital admission, this study clearly showed that older age was not the only factor that affected the need for hospital care in this study group. HIV-positive people should keep in mind the other factors that raised the risk of hospital admission in this study group (Tables 1 and 2). For example, African Americans with and without HIV have a higher risk of kidney disease than whites. And this study confirmed that higher risk.

Among the risk factors that a person can change, CD4 count may be the most important. A U.S. government panel now recommends that anyone with HIV start antiretroviral therapy -- whatever their CD4 count.6 This study demonstrates that a CD4 count under 350 raises chances of hospital admission with both AIDS illnesses and non-AIDS illnesses.


  1. Berry SA, Fleishman JA, Moore RD, Gebo KA, for the HIV Research Network. Trends in reasons for hospitalization in a multisite United States cohort of persons living with HIV, 2001-2008. J Acquir Immune Defic Syndr. 2012;59:368-375.
  2. Betz ME, Gebo KA, Barber E, et al. Patterns of diagnoses in hospital admissions in a multistate cohort of HIV-positive adults in 2001. Med Care. 2005;43(9 suppl):III3-III14.
  3. Yehia BR, Fleishman JA, Hicks PL, et al. Inpatient health services utilization among HIV-infected adult patients in care 2002-2007. J Acquir Immune Defic Syndr. 2010;53:397-404.
  4. Mayo Clinic health information. Pneumonia. Risk factors.
  5. Engsig FN, Hansen AB, Gerstoft J, et al. Inpatient admissions and outpatient visits in persons with and without HIV infection in Denmark, 1995-2007. AIDS. 2010;24:457-461.
  6. HHS Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. March 27, 2012.