Human Immunodeficiency Virus Infection
Infection caused by one of two related retroviruses (HIV-1 and HIV-2) resulting in a wide range of clinical manifestations related to defective cellular immunity.
In the USA, an estimated 10% of AIDS cases occur in persons >= 50 years; 3% of all AIDS cases occur in patients > 60. AIDS cases are increasing in the over-50 population: From 1990 to 1992, new AIDS cases decreased 3% among persons <= 30 but increased 17% among those >= 60.
Early in the epidemic, most elderly persons with HIV infection acquired it from blood transfusions; however, transmission by this route has decreased dramatically since the introduction of donor screening procedures. HIV infection in elderly persons is now most commonly transmitted through sexual activity. In the USA, homosexual and bisexual men constitute the largest group (about 35%) of AIDS cases among elderly persons. Heterosexual transmission of HIV has also increased among elderly persons: it accounted for only 6% of AIDS cases among elderly persons in 1988 but for 12% in 1994. Heterosexual high-risk behavior (eg, sex with prostitutes) may be more common among elderly persons living in urban environments.
Most sexually active elderly persons are no longer concerned about contraception and do not perceive themselves as being at risk of HIV infection. They are one sixth as likely as persons in their 20s to use condoms during intercourse.
Pathogenesis
HIV virus belongs to the family of human retroviruses, which contain an enzyme called reverse transcriptase that converts viral RNA into a proviral DNA copy that becomes integrated into the host cell DNA. The hallmark of HIV infection is a profound immunodeficiency resulting predominantly from a progressive decrease in the number of the CD4+ subset of T lymphocytes, referred to as helper or inducer cells. This subset is defined phenotypically by the presence on its surface of a CD4 molecule, which is the cellular receptor for HIV. When the CD4+ T-lymphocyte count decreases below a certain level (usually < 200/µL [< 0.2 × 109/L]), patients become vulnerable to developing a variety of life-threatening opportunistic infections, such as Pneumocystis carinii pneumonia, cryptococcal meningitis, candidiasis, cytomegalovirus, encephalitis, and cancers such as lymphoma and Kaposi's sarcoma.
Symptoms, Signs, and Diagnosis
The clinical manifestations of HIV infection in elderly patients are similar to those in younger patients. Some of the early symptoms of HIV infection (eg, fatigue, anorexia, weight loss, memory problems) are nonspecific and may be attributed to other diseases that are common in old age. As a result, appropriate diagnostic evaluation is often delayed (typically up to 10 months) in some elderly patients. Also, the elderly are one fifth as likely as persons in their 20s to be tested for HIV infection.
HIV infection is diagnosed by the detection of HIV itself, antibodies to HIV, or one of HIV's components. Antibodies to HIV generally appear in the circulation 4 to 8 weeks after infection. The standard screening test for HIV is the enzyme-linked immunosorbent assay (ELISA--sensitivity > 99.5%). A positive ELISA result must be confirmed by the Western blot test, a more specific assay. Testing for p24 antigen, a marker for viral replication, may detect HIV in the early stages of infection. Polymerase chain reaction is a highly sensitive gene amplification technique that may identify HIV in patients with latent infection or no detectable antibody to HIV.
AIDS is diagnosed by a positive serology for the HIV-1 virus and a CD4+ T-lymphocyte count < 200/µL (< 0.2 × 109/L) or by the presence of an AIDS-indicator disease. There is little difference in the initial AIDS-defining diagnosis between younger and older patients; the most predominant AIDS indicator diseases across all age groups are Pneumocystis carinii pneumonia (in 75% of all cases) and candidal esophagitis (in 15%). Other AIDS-indicator diseases in the elderly include extrapulmonary cryptococcosis, toxoplasmosis of the brain, cytomegalovirus disease, tuberculosis, recurrent bacterial pneumonia, Mycobacterium avium complex infection, and Kaposi's sarcoma. However, an indolent form of Kaposi's sarcoma occurs in elderly men without evidence of HIV infection. Cryptococcal meningitis may have subtle clinical manifestations in elderly patients and few, if any, symptoms. Headaches and lethargy may be the only complaints, and meningeal signs occur in < 30% of cases. In wasting syndrome, another AIDS-indicator disease, weight loss > 10% is accompanied by chronic diarrhea, weakness, and fever unexplained by other causes.
HIV-associated dementia, also known as HIV encephalopathy, is a neurologic disorder caused by the direct effect of the HIV virus on the central nervous system. Progressive dementia may occur as the HIV infection progresses. Although HIV-associated dementia usually occurs in the later stages of AIDS, it is the presenting symptom in as many as 10% of all cases. HIV-associated dementia occurs more frequently among elderly patients, in whom Alzheimer's disease may be misdiagnosed. HIV-associated dementia, however, differs from Alzheimer's disease in several ways (see Table 134-1).
Prevention, Prognosis, and Treatment
Practically no prevention information on AIDS is targeted at elderly persons, although most elderly persons are sexually active. Elderly persons engaging in risky sexual practices should use the same precautions (eg, use of condoms or vaginal barriers, avoidance of exposure to semen) as younger persons. Hormonal changes after menopause make the vaginal lining thinner and less likely to protect against HIV if a woman has sex with an infected person.
HIV infection progresses more rapidly to AIDS and survival rates are poorer among elderly patients than among younger patients. Cumulative survival rates decrease as age increases. The 1-year survival rate is 80% in younger patients but only 40% in elderly patients.
Why elderly patients with AIDS do worse than younger patients is unclear. Comorbidity, late diagnosis, inadequate treatment, and decreased adherence to antiretroviral therapy may play a role. Of particular interest are age-related changes in the immune system; normally, CD4+ counts do not decrease and may increase. However, at the time of AIDS diagnosis, elderly patients have lower CD4+ counts than younger patients do. This precipitous decrease may be due to impaired T-lymphocyte replacement mechanisms secondary to thymic involution or other age-related hematologic changes.
Aggressive antiretroviral therapy with combination treatment regimens and opportunistic infection prophylaxis, similar to that used in younger patients, is recommended for elderly patients with AIDS. Elderly patients may even require a more aggressive approach to therapy than do younger patients, with earlier use of combination therapies; the elderly appear to respond equally well to combination therapy as younger persons. However, elderly patients are rarely included in clinical trials, and no specific recommendations have been published on the use of antiretroviral therapy in elderly persons. Furthermore, drug toxicities and interactions with drugs used for other conditions are more common in elderly persons.
An interdisciplinary care approach, including psychologic and social support, helps manage HIV infection in elderly patients. These patients should be counseled, when appropriate, regarding safe sexual behavior, and condom use should be emphasized for those who are sexually active.
Long-Term Care
Hospitals and community-based resources provide only a portion of the continued care that AIDS patients require. Long-term care services are increasingly needed for the continued care of AIDS patients, old or young. For example, nursing homes, which traditionally provide skilled nursing care for chronically ill elderly patients, can provide similar care for AIDS patients of all ages. An estimated 10 to 25% of AIDS patients require this type of care, and the number is increasing. However, many nursing homes are reluctant to admit AIDS patients because few personnel are properly trained to care for them, the cost of care is high because of the use of disposable items, and a fear for the safety of other patients and their families may exist.
Personnel who care for AIDS patients in long-term care facilities should follow infection control guidelines. These guidelines are best implemented through general education programs for all personnel, patients, and family members and through on-site training for personnel in the specific units caring for AIDS patients. |
