What is the goal of the MACS/WIHS Combined Cohort Study?

The Multicenter AIDS Cohort Study (MACS) / Women’s Interagency HIV Study (WIHS) Combined Cohort Study (MACS/WIHS-CSS) is a collaborative research effort that aims to understand and reduce the impact of chronic health conditions—including heart, lung, blood, and sleep (HLBS) disorders—that affect people living with HIV.

For decades, the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health (NIH), has supported the separate MACS and WIHS cohort studies. MACS was a study of gay and bisexual men, while WIHS was a study of women who had other risk factors for HIV.

In 2019, the NHLBI became the primary steward of the new MACS/WIHS-CSS. For this effort, the NHLBI is working in close collaboration with the NIH Office of AIDS Research (OAR) as well as several co-funding institutes across the NIH.


  • About 1.1 million people age 13 and older in the United States and almost 37 million people worldwide are living with HIV.
  • Almost half of the people living with HIV in the United States are 50 or older.
  • The Combined Cohort Study will advance the basic and clinical science of HIV and focus on chronic conditions that occur in people living with HIV.
  • The Combined Cohort Study will include continuing participants from the earlier, separate MACS and WIHS studies.
  • The study will recruit participants from groups that were underrepresented in previous studies, such as blacks, Hispanics, and residents of southern states.
  • MACS and WIHS investigators have published over 2,000 articles on HIV-related topics such as immunology, HIV prevention, cancers, and cardiovascular diseases.

How is the MACS/WIHS Combined Cohort Study contributing to scientific discovery?

Today, people living with HIV are more likely to develop chronic diseases than AIDS-related diseases. They have an increased risk of developing mental health and neurologic illnesses, diabetes, kidney failure, liver disease, cardiovascular diseases, lung diseases such as pulmonary hypertension and COPD, sleep disorders, anemias and other blood-related disorders, as well as some cancers. These conditions will be a sustained focus of the Combined Cohort Study. The program aims to make these research advances:

  • Identify biomarkers of increased risk for chronic disorders in people living with HIV.
  • Determine how antiretroviral therapy (ART) affects other medical conditions, including the timing of treatments after HIV infection.
  • Develop strategies for more effective interventions and treatments.
  • Learn about the role of chronic immune activation and inflammation due to HIV infection in other health conditions.
  • Study HIV as a possible research model for accelerated aging.

Investigators from the previously separate MACS and WIHS studies have made groundbreaking discoveries in the field of HIV research, including how best to diagnose and manage HIV; the link between low immune cell counts and AIDS; and genetic , metabolic , and other factors that influence how HIV infection may progress to the active diseases of AIDS. Dedicated individuals who are living with and without HIV have been critical to these life-saving discoveries, and their continued participation, as part of the Combined Cohort Study, is central to further HIV research.

The Combined Cohort Study aims to spur new scientific discoveries by sharing data and biospecimens from the MACS and WIHS research groups. The NHLBI encourages early career investigators to use these resources for innovative research ideas and to generate preliminary data for large grant applications. Learn more about HIV/AIDS-related research applications.

The Combined Cohort Study complements ongoing research efforts supported by the broader NHLBI HIV/AIDS Program. The program provides global leadership for research, training, and education activities that specifically promote studies about HIV-related heart, lung, blood, and sleep disorders, as well as blood-based therapies.

How can researchers access MACS/WIHS Combined Cohort Study data?

Researchers can request access to data and biospecimens through the MACS/WIHS Combined Cohort Study Data Analysis and Coordinating Center (DACC). Biospecimens available include serum, plasma, cells, and urine. These biospecimens come from men and women in the MACS/WIHS Combined Cohort Study, as well as from past participants of the separate MACS and WIHS studies.

Researchers can submit a concept sheet to the Combined Cohort Study Executive Committee. Once the committee reviews and approves the concept sheet, the DACC helps coordinate the delivery of datasets and biospecimens to the researcher and may provide analytic support.

How does the MACS/WIHS Combined Cohort Study work?

Since 1984, more than 12,000 people have participated in MACS and WIHS. The MACS/WIHS Combined Cohort Study will build upon the information gathered from these participants while redirecting research to investigate co-existing medical conditions that often affect people living with HIV today. The Combined Cohort Study includes continuing participants from the earlier studies. Researchers will also recruit new participants with a special focus on hard-hit population groups, such as black and Hispanic men and women and residents of southern states.

More Information
- MACS/WIHS Combined Cohort Study

Multicenter AIDS Cohort Study (MACS)

MACS started in 1984 and enrolled over 7,000 men who were living with and without HIV at study centers located in Baltimore, Md., Chicago, Ill., Pittsburgh, Pa., and Los Angeles, Ca. Every six months, participants answered questions about their health and social behaviors; provided blood samples; received a physical exam and cognitive function evaluation; among other tests. Some of the scientific accomplishments of this landmark study include:

  • Strategies to diagnose HIV infection
  • Evaluation of highly active antiretroviral therapy (HAART) to treat HIV
  • The role of an individual’s genetics on treatment effectiveness
  • Evaluation of treatments for HIV-related illnesses such as pneumocystis pneumonia (PCP)
  • Development of HIV treatment guidelines
  • Evaluation of strategies to improve treatment adherence
  • Evaluation of interventions to prevent HIV infection in high risk individuals
  • The relationship between HIV and aging
  • The role of HIV infection in developing other diseases, including cardiovascular disease, kidney disease, and certain cancers

Women’s Interagency HIV Study (WIHS)

WIHS started in 1993 and has enrolled almost 5,000 women who were living with and without HIV at clinical centers in Atlanta, Ga.; Birmingham, Ala.; Brooklyn, NY; Chapel Hill, N.C.; Jackson, Miss.; Miami, Fla.; New York, N.Y.; Chicago, Ill.; Los Angeles, Ca.; San Francisco, Ca.; and Washington, D.C. This study was designed to look at the progression of HIV disease in women. A follow-up visit every six months included, but was not limited to, questions on medical history, alcohol and drug use, and sexual behaviors. They also had a physical exam and provided blood, cervical, and urine samples. Some of the scientific accomplishments of WIHS include:

  • Discovery of genetic, metabolic, and behavioral factors that influence HIV progression
  • Exploration of key differences in HIV infection between women and men
  • Identification of differences in HIV disease and treatment outcomes between men and women and in different racial and ethnic groups
  • Discovery of barriers that prevent women with HIV from taking lifesaving HAART medicines daily as prescribed
  • Evaluation of the health effects of other viruses such as herpes, hepatitis C, and human papillomaviruses in women living with HIV
  • The role of HIV infection in the treatment and outcomes of other medical conditions, including cardiovascular, liver, and kidney diseases, pregnancy, and cancer
  • Research into the ways HIV affects clinical outcomes for women across their lifespan