In 1991, the Women’s Health Initiative (WHI), sponsored by the National Heart, Lung, and Blood Institute (NHLBI), was launched. The original WHI study had three parts—a clinical trial, an observational study, and a community prevention study—and completed data collection in 2005. The WHI continues to contribute to the science of women’s health through extension and ancillary studies.

The WHI is a long-term national health study that focuses on strategies for preventing heart disease, breast and colorectal cancer, and osteoporosis in postmenopausal women. These chronic diseases are the major causes of death, disability, and frailty in older women of all races and backgrounds.

The initiative’s extension studies collect long-term data from 52,068 WHI volunteers to complement the original WHI study. The current extension study collects annual health information from WHI volunteers who agree to take part through 2026, with a focus on heart disease, cardiovascular events, and aging.

On April 25, 2025, WHI leaders announced that National Institutes of Health (NIH) contracts supporting its regional centers were being terminated in September and that the study’s clinical coordinating center, based at the Fred Hutchinson Cancer Center in Seattle, “will continue operations until January 2026, after which time its funding remains uncertain.”

They added that the contract terminations for its four main sites “will significantly impact ongoing research and data collection … severely limit[ing] WHI’s ability to generate new insights into the health of older women, one of the fastest-growing segments of our population.” (There are about 55 million postmenopausal women in the United States.)