Women's Health Initiative Timeline (1991–2026): Every Key Date, Trial and Finding

By The HRT Index Editorial Team Editorial research — not medically reviewed Published: August 3, 2026 · Last verified: August 3, 2026 · Dataset version: 1.0

There is no single date on which the Women's Health Initiative started, and no single date on which it stopped.

That is the finding this Women's Health Initiative timeline is built around. The program was announced on April 19, 1991, enrolled 161,808 postmenopausal women between 1993 and 1998, and — according to the National Heart, Lung, and Blood Institute, the study's sponsor — is still collecting annual health information through 2026, with long-term extension data from 52,068 volunteers. In between, its two hormone interventions were stopped early, two years apart, and later follow-up produced opposite breast cancer findings for the two tested regimens.

The date problem is bigger than it looks. The 2002 estrogen-plus-progestin transition spans six source-backed milestones if the later July 7 intervention endpoint and the July 8 study-drug discontinuation are kept separate: an April 30 data cutoff, a May 31 safety-board recommendation, a July 7 endpoint used in later analyses, July 8 drug discontinuation and participant instruction, a July 9 public announcement, and a July 17 journal publication. The 2004 estrogen-alone transition spans five more: a February 2 agency decision, a February 29 analysis cutoff, a March 1 participant notice and stop instruction, a March 2 public announcement, and an April 14 publication.

They are not contradictions. They are different events.

We assembled them as different events, dated, with the primary source attached. And in doing so we found something the standard histories miss: when checked on August 3, 2026, the WHI's own published “Journey through WHI's history” timeline ended in 2023 — before the funding sequence of 2025 and before the FDA's 2025–2026 hormone-label revision process.

Women's Health Initiative statistics: the five-minute version

WHI enrolled 161,808 women, stopped its two hormone interventions in separate 2002 and 2004 sequences, completed original data collection in 2005, and continued extension follow-up through 2026. The table below gives the dates and denominators most likely to be needed in one place.

Original dataset finding: “The WHI stopped in 2002” compresses at least six dated milestones into one. “The estrogen-alone trial stopped in 2004” compresses five more. This timeline keeps the decision, endpoint, stop instruction, announcement and publication separate.

One boundary before the full chronology. The WHI hormone trials tested two specific oral regimens: conjugated equine estrogens at 0.625 mg/day plus medroxyprogesterone acetate at 2.5 mg/day in women with a uterus, and conjugated equine estrogens at 0.625 mg/day alone in women with prior hysterectomy. They did not directly test transdermal patches or gels, vaginal estrogen, micronised progesterone, or the other doses and formulations used now. The trials were designed mainly to test chronic disease prevention, not to test how well hormone therapy relieved hot flashes.

What is the Women's Health Initiative timeline?

The Women's Health Initiative timeline begins with the program's announcement on April 19, 1991, runs through recruitment of 161,808 postmenopausal women aged 50 to 79 between 1993 and 1998, includes separate hormone-intervention transitions in 2002 and 2004, the completion of original data collection in 2005, and extension follow-up and long-term analyses through 2026. It also includes the regulatory chapter: FDA's classwide hormone-label changes beginning in 2003 and the 2025–2026 process that revised the first product labels.

Below is the full chronology. Every row carries four things: what kind of event it was, which part of the WHI it concerned, what the primary source supports, and — crucially — what the event does not establish.

That last column is the difference between “the WHI found hormone therapy raises breast cancer risk” and “one WHI trial, testing one oral combination in women with a uterus, reported a higher rate of invasive breast cancer.”

Era 1 — Founding, design and recruitment (1991–1999)

A note on the recruitment window, because it is quoted inconsistently. Modern WHI summaries use 1993–1998. The 2007 cardiovascular timing analysis says women were recruited between September 1993 and October 1998, while component records use different completion dates because the randomized components did not all open and close together. We publish the canonical year range rather than inventing one program-wide final recruitment day.

Era 2 — The estrogen-plus-progestin intervention stops (2000–2003)

Era 3 — The estrogen-alone intervention stops and extension begins (2003–2005)

Era 4 — The other trials and long-term follow-up (2006–2024)

Era 5 — Funding, regulation and the present (2025–2026)

We did not identify this complete 2025–2026 sequence in the WHI chronologies reviewed for this build, including the dated timeline on the WHI's own About page.

What this timeline shows — and what it doesn't

This timeline shows what happened, when, to which part of the WHI, and under what conditions. It does not turn a chronology into medical advice, and it does not extend results from two specific oral regimens to every hormone product on the market today.

Three boundaries are worth stating plainly, because they are the three most common ways this history gets flattened.

The WHI was one program, not one trial. The original program had three parts — a clinical trial, an observational study and a community prevention study. The clinical-trial part contained three randomized trials, and eligible participants could join one, two or all three of them.

The randomized-trial counts overlap. A participant could enroll in one, two or all three randomized components, so 27,347 plus 48,835 plus 36,282 is not a valid total-participant calculation.

The two hormone trials had different populations and different long-term breast cancer findings. CEE plus MPA, in women with a uterus, was associated with higher invasive breast cancer incidence. CEE alone, in women with prior hysterectomy, was associated with lower incidence and lower breast cancer mortality during long-term follow-up. Reporting those as one result is the single most consequential error in WHI coverage.

The hormone trials were designed for chronic disease prevention, not symptom-treatment effectiveness. The 2024 JAMA review states that the trials do not support the tested oral regimens for prevention of cardiovascular disease, dementia or other chronic diseases. The same review distinguishes that question from treatment of bothersome menopausal symptoms, an FDA-approved use the WHI was not designed to evaluate directly.

How we built this timeline

We took each event from the issuing body's own material where one exists — WHI and NIH/NHLBI records, FDA actions, the trial registry, and original journal publications. Where credible sources used different dates, we did not force them into one. We recorded what kind of event each date describes.

That last decision is the method, so here it is in full.

We classify dates into thirteen event layers:

1. Program announcement
2. Design and program operations
3. Recruitment or randomization
4. Safety notice or safety review
5. Safety-board recommendation
6. Agency decision
7. Data cutoff or intervention endpoint
8. Study-drug discontinuation or participant stop instruction
9. Participant communication
10. Public announcement
11. Journal publication or follow-up analysis
12. Extension, ancillary-study or program-funding status
13. Regulatory panel, labeling request or product-specific approval

Once a date is assigned a layer, most apparent contradictions dissolve. “The estrogen-alone trial was stopped in February 2004” and “the estrogen-alone trial was stopped in March 2004” can both be accurate, but they are incomplete. February 2 was the NIH decision. February 29 was the analysis cutoff and intervention endpoint used in later analyses. March 1 was the participant notice and stop instruction. March 2 was the public announcement. April 14 was the principal publication.

Our source hierarchy, in order:

1. The original randomized trial report, protocol or prespecified follow-up report
2. Official WHI, NIH/NHLBI, FDA or trial-registry records — WHI is registered as NCT00000611
3. Original long-term follow-up publications
4. Modern WHI syntheses, used to frame what the body of evidence does and does not support
5. Contemporaneous institutional announcements, used for operational and public-announcement dates

Date precision. An event stays year-only or range-only when the primary record does not support an exact day. We do not turn “1993–1998” into a fabricated enrollment endpoint, and we do not treat a journal-publication date as the date an intervention stopped.

Current verification. Program status, participant counts and FDA label actions are true only as of a date. Those rows carry an August 3, 2026 verification date and must be rechecked when the page is updated.

What the “what it does not establish” column is. It is our editorial synthesis, constrained by the trial population, randomization design, formulation, dose, route, age at enrollment, hysterectomy status, treatment purpose, endpoint, and whether an analysis was prespecified or secondary. It is not clinical advice and not a quotation from the investigators.

Why do sources give different dates for when the WHI trials stopped?

Because “stopped” describes a chain of different events that happened on different days. For the estrogen-plus-progestin trial, the source record runs from an April data cutoff to a July publication. For the estrogen-alone trial, the decision, analysis cutoff, participant instruction, public announcement and publication were also separate.

Here is the reconciliation, side by side.

Two rows deserve a note.

July 7 versus July 8, 2002. The 2020 breast cancer follow-up uses July 7 as the intervention endpoint in its treatment-duration plot. The 2003 WHIMS report says study drug was discontinued on July 8 and includes events through that date. Those are not interchangeable descriptions. July 7 is the later analytical endpoint; July 8 is the explicit drug-discontinuation and participant-instruction date; July 9 is the public-announcement date.

6.8 years versus 7.1 or 7.3 years. The principal 2004 estrogen-alone report gives an average of 6.8 years for outcomes available through February 29. Later papers describe the intervention using medians or longer completed follow-up and report 7.1 or 7.3 years. The values are not arithmetic errors; they reflect different summaries and analysis records.

What do the Women's Health Initiative data actually show?

The estrogen-plus-progestin trial reported, per 10,000 person-years, 7 more coronary heart disease events, 8 more strokes, 8 more pulmonary embolisms and 8 more invasive breast cancers, alongside 6 fewer colorectal cancers and 5 fewer hip fractures — a net excess of 19 events per 10,000 person-years on the trial's global index. The estrogen-alone trial reported 12 additional strokes and 6 fewer hip fractures per 10,000 person-years, with no significant effect on coronary heart disease and a nonsignificant lower point estimate for breast cancer.

Absolute and relative measures answer different questions. Both are shown below so the size of an effect is not hidden behind a percentage.

The 2002 estrogen-plus-progestin results

Estrogen plus progestin versus placebo, 16,608 women with a uterus, mean 5.2 years.

The paper's own absolute-risk summary was: 7 more coronary events, 8 more strokes, 8 more pulmonary embolisms and 8 more invasive breast cancers, with 6 fewer colorectal cancers and 5 fewer hip fractures per 10,000 person-years. The global index produced 19 excess events per 10,000 person-years.

The 2004 estrogen-alone results

Estrogen alone versus placebo, 10,739 women with prior hysterectomy, average 6.8 years.

The estrogen-alone global-index point estimate was 1.01, with a 95% confidence interval of 0.91–1.12. That is no significant overall difference. The intervention was stopped because stroke risk was elevated and there was little prospect of demonstrating a coronary benefit in the time remaining — not because its global index had crossed the same kind of harm boundary as the combined-hormone trial.

The breast cancer number, and the two confidence intervals almost nobody prints together

This is the most contested number in the WHI's history, and the original paper contains a detail that explains part of the later argument.

The 2002 report gave the invasive breast cancer hazard ratio as 1.26. It printed two confidence intervals in Table 2 and Figure 3: a nominal 95% CI of 1.00–1.59, and an adjusted 95% CI of 0.83–1.92. The adjusted interval is wider because the trial used sequential monitoring and evaluated multiple outcomes.

The paper itself said the 26% increase “almost reached nominal statistical significance,” while the weighted monitoring statistic for breast cancer crossed the prespecified stopping boundary. HHS's November 10, 2025 announcement described the initial breast cancer increase as statistically nonsignificant. That description is consistent with the adjusted interval crossing 1.0; it does not erase the nominal interval, the monitored stopping rule, the global-index result, or the later follow-up.

We are not adjudicating the label dispute in this table. We are recording the statistical record the original paper actually printed: one hazard ratio, two confidence intervals, and a separate monitored stopping statistic.

What the same randomized cohorts showed with longer follow-up

The 2020 paper's authors wrote that prior CEE-alone use was, to their knowledge, the first pharmacologic intervention shown to be associated with a statistically significant reduction in deaths from breast cancer. That finding is about one oral estrogen regimen, in women with prior hysterectomy, after a median intervention duration of about 7.2 years and long follow-up. The same trial also reported increased stroke risk during intervention, and the WHI does not support CEE alone for chronic disease prevention.

The WHIMS dementia finding in absolute terms

Among women age 65 or older in WHIMS, probable dementia was diagnosed at annualized rates of 45 per 10,000 person-years with CEE plus MPA and 22 per 10,000 person-years with placebo — an absolute difference of 23 additional diagnoses per 10,000 person-years and an HR of 2.05 (95% CI 1.21–3.48). There were 61 probable dementia cases in the analysis. The result does not answer what happens when hormone therapy is started near menopause because WHIMS enrolled women age 65–79.

Source: Shumaker et al., JAMA 2003;289(20):2651–2662. Verified August 3, 2026.

What the non-hormone randomized trials found

Where official WHI figures look inconsistent — and what they are actually counting

Official WHI and NIH records sometimes publish different numbers or dates for what looks like the same fact. Most of these are not true contradictions. They are different event definitions, different statistical summaries, different enrollment phases, or different participant denominators.

The funding sequence is the clearest example of why this method matters. On April 21, 2025, WHI announced that the four Regional Center contracts would not be renewed. Reports of a reversal appeared three or four days later. But WHI's April 25 update said it had received no confirmation from NIH “in any form.” WHI did not report confirmation through its acquisitions officer until May 6, 2025.

Fifteen days, not three. Both dates are real. One describes a reported statement to the press; the other describes confirmation through the study's contracting channel.

Is the Women's Health Initiative still running?

Yes. As last verified on August 3, 2026, NHLBI states that the current WHI extension study collects annual health information from volunteers who agree to participate through 2026, and that the extension studies contain long-term data from 52,068 volunteers.

That wording needs to stay exact. “Runs through 2026” does not mean “permanently ends in 2026.” It documents the current study period described by NHLBI. It does not promise continuation beyond 2026, and it does not announce a shutdown at the end of the year.

The participant counts also need their labels. NHLBI's 52,068 figure describes volunteers represented in the long-term extension data. WHI separately said in its April 2025 funding announcement that more than 42,000 women were actively involved, then ages 78 to 108. Those are different populations measured for different purposes.

The funding record has one remaining public gap. WHI's April 2025 announcement referred to Regional Center contracts through September 2025 and Clinical Coordinating Center funding through January 2026, followed by a May 6 statement that the nonrenewal had been rescinded and new task orders could proceed. We did not locate a later WHI or NIH public statement that narrates those individual contracting milestones after May 6. The current NHLBI program page nevertheless states that the extension study operates through 2026. We publish both records rather than turning one into details the other does not supply.

How did the WHI change hormone therapy labels — and what changed in 2025 and 2026?

FDA began approving classwide hormone-therapy labeling changes in 2003 after the WHI hormone-trial findings. On November 10, 2025, FDA requested new revisions to menopausal hormone-therapy labels. On February 12, 2026, it approved revised labeling for the first six products after 29 companies submitted proposed changes. When checked on August 3, 2026, FDA's updated-prescribing-information page listed those same six products.

The regulatory sequence is separate from the clinical-trial sequence. A label request is not a product approval, and a product approval does not rewrite the historical WHI results.

Two cautions belong beside any summary of this process.

“FDA removed the boxed warning” compresses a staged process. The November 2025 action was a request to application holders. The February 2026 announcement covered the first six approved product labels. The six-product page is a verified snapshot, not proof that no additional action exists outside that page or will occur later.

Not every warning or risk statement disappeared. FDA retained the boxed warning about endometrial cancer for systemic estrogen-alone products. The agency also said cardiovascular disease and breast cancer information would remain elsewhere in systemic-product labeling even when removed from the boxed warning, while probable dementia language was to be removed across the label under the requested changes.

Who has said what about the 2025–2026 label change?

The principal public positions do not agree. FDA leadership defended a more differentiated label, WHI took no position on the boxed-warning decision, two research organizations supported the action, and nine former WHI safety-board members challenged the process and called for formal advisory review.

The WHI statement is the easiest one to misstate. It did not endorse the FDA action. It did not condemn it. It repeated the boundary its trials support: the tested oral regimens should not be used for chronic disease prevention, and those trials did not evaluate every modern product, route or symptom-treatment situation.

What did the WHI hormone trials not test?

The WHI hormone trials did not directly test transdermal estradiol patches or gels, vaginal estrogen products, micronised progesterone, most current doses, or a trial population selected specifically for starting treatment before age 60 or within 10 years of menopause. They also were not designed to determine how effectively hormone therapy treated hot flashes or other menopausal symptoms.

The actual randomized regimens were narrow and explicit:

• Oral conjugated equine estrogens, 0.625 mg/day, plus oral medroxyprogesterone acetate, 2.5 mg/day, in women with a uterus
• Oral conjugated equine estrogens, 0.625 mg/day, alone in women with prior hysterectomy

The women were ages 50–79 at enrollment, with a mean age of about 63. The trials did include women in their fifties, but they were not designed around the modern clinical question of beginning symptom treatment near menopause. Their primary purpose was to test whether the regimens prevented major chronic diseases and fractures.

The 2007 age-and-timing paper explored whether cardiovascular effects varied by age and years since menopause. It was a secondary analysis, and a correction followed in 2008. It suggested that coronary effects may differ by timing, but it did not prove that starting hormone therapy near menopause prevents coronary heart disease. Stroke risk remained elevated overall in the pooled analysis.

A 2025 secondary analysis asked a narrower question using the original cohorts: what happened among women who had moderate or severe vasomotor symptoms? Among women age 50–59, neither randomized regimen significantly altered atherosclerotic cardiovascular disease risk; among women age 70 or older with symptoms, risk was increased. That is useful subgroup evidence. It is still a reanalysis of the original two oral regimens, not a new trial of contemporary formulations.

Why does this Women's Health Initiative timeline matter now?

Because the same evidence record now sits behind two live questions: how menopausal hormone products should be labeled, and how the WHI itself continues as a long-term research program. Both questions collapse into slogans when the dates, regimens and denominators are stripped away.

The 2002 combined-hormone result changed prescribing and public understanding. A 2014 economic model estimated that the resulting changes from 2003 through 2012 produced a $37.1 billion net economic return, including $35.2 billion in lower direct medical costs, 126,000 fewer breast cancer cases and 76,000 fewer cardiovascular disease cases. Those are model outputs, not observed WHI case counts, but they show the scale of the policy and treatment changes attributed to one trial publication.

The 2025–2026 label debate returned to the same record. FDA emphasized age, timing, formulation and indication. WHI emphasized that no comparably large randomized trial had displaced the overall findings for the two oral regimens it tested. Former safety-board members emphasized the absence of a formal advisory-committee process and the need to preserve product-specific risk information. All of them were discussing the same trials, but not always the same endpoint, confidence interval, population or stage of follow-up.

That is why the chronology is not decoration. It is the minimum structure needed to tell a decision date from a publication date, one regimen from another, a randomized result from a secondary analysis, and a regulatory request from an approved product label.

Limitations

This timeline is a source-normalized reference, not a complete bibliography or an individualized treatment guide. Its strongest claims are the dated event distinctions; its main limits are changing current-status records, different participant denominators, and the boundaries of the two oral regimens actually tested.

We would rather you know these upfront.

1. This is a curated chronology, not a bibliography. WHI reported more than 2,400 publications by 2025. We include events that changed the program's state, marked a principal decision or publication, materially changed interpretation, or recorded a consequential regulatory action.
2. Publication dates are not intervention dates. This page separates them. Many summaries do not.
3. The events after 2023 were assembled from separate primary records. The dated chronology on WHI's About page ended with Long Life Study 2 in 2023 when checked August 3, 2026. WHI's news pages and FDA records contain later events.
4. Current funding detail is incomplete in the public record we located. WHI confirmed the reversal of nonrenewal on May 6, 2025, and NHLBI says the current extension operates through 2026. We did not locate a public WHI or NIH narrative resolving each contract milestone mentioned in the April announcement.
5. Official participant counts use different denominators. NHLBI's 52,068 figure describes long-term extension data; WHI's more-than-42,000 figure described active involvement in 2025. Neither should be silently relabeled as the other.
6. The FDA product count is a dated register snapshot. The FDA page listed six products on August 3, 2026. That page is not proof that no other product-specific action exists elsewhere.
7. Long-term analyses reuse the original randomized cohorts. They are not new randomized trials. Later follow-up can involve reconsent, attrition and different outcome-collection methods.
8. Clinical interpretation stays tied to what was tested. Population, hysterectomy status, regimen, dose, route, purpose, endpoint and timing all matter.
9. The nominal and adjusted confidence intervals are both part of the 2002 record. The breast cancer intervals are reproduced from Table 2 and Figure 3 of the principal JAMA report. The stopping decision also used a monitored boundary and the global index.
10. This is educational reference material, not medical advice. Nothing here determines whether one person should start, stop or change hormone therapy. That requires a clinician who knows the person's symptoms, history, risk factors and treatment goals.

Claims we deliberately do not make

For transparency, these are things the source record does not support as written:

• That there is one correct WHI stop date. There are separate review, decision, endpoint, participant-notice, announcement and publication dates.
• That the WHI proved every form of hormone therapy is dangerous. It randomized two oral regimens in two defined populations.
• That the entire WHI ended in 2002 or 2005. One hormone intervention ended in 2002; the other ended in 2004; original data collection was completed in 2005; extension work continued.
• That the 2007 analysis proved the timing hypothesis. It was secondary and exploratory.
• That FDA changed every hormone-therapy label on November 10, 2025. That date was a labeling request. The first six approvals were announced February 12, 2026.
• That 52,068 women were all actively participating on August 3, 2026. NHLBI describes that number as volunteers represented in extension-study data.
• That WHI funding is guaranteed beyond the period documented by current official sources.
• That one confidence interval settles the 2025–2026 label dispute. The original report printed nominal and adjusted intervals and used a separate monitoring rule.
• That the long-term breast cancer findings apply to untested formulations or women without the corresponding trial characteristics.
• An unsourced estimate of how many women personally stopped treatment because of the 2002 publication.

Frequently asked questions

These answers resolve the most common factual errors in the WHI chronology: treating one intervention stop as the end of the program, combining the two hormone regimens, or confusing a decision date with an announcement or publication date. Each answer is a compressed version of the sourced tables above.

When did the Women's Health Initiative begin?

Plans were announced on April 19, 1991, by NIH Director Bernadine Healy. Design and program operations developed during 1991–1992, and recruitment began in September 1993. Sources using 1991, 1992 or 1993 as “the start” are describing different milestones.

When did the Women's Health Initiative end?

The broader program has not been documented as ending. Original WHI data collection was completed in 2005, followed by extension and ancillary studies. As last verified August 3, 2026, NHLBI says the current extension collects annual health information through 2026 and contains long-term data from 52,068 volunteers.

Was the whole WHI stopped in 2002?

No. The estrogen-plus-progestin intervention stopped in 2002. The estrogen-alone intervention continued until 2004, and the dietary, calcium-plus-vitamin-D, observational and ancillary components continued on their own schedules.

Why was the estrogen-plus-progestin trial stopped?

The Data and Safety Monitoring Board concluded that the prespecified breast cancer monitoring boundary had been crossed and that the global balance of measured risks and benefits favored harm. It recommended stopping on May 31, 2002. Study drugs were discontinued July 8, the public announcement came July 9, and the principal paper was published July 17.

Why was the estrogen-alone trial stopped?

Stroke risk was elevated, and the trial was unlikely to demonstrate a coronary heart disease benefit in the remaining time. NIH decided on February 2, 2004. The principal analysis used data through February 29; participants were informed and told to stop on March 1; the public announcement came March 2.

How many women took part in the WHI?

161,808. Of those, 68,132 participated in one or more randomized clinical trials and 93,676 entered the observational study. The two hormone trials together involved 27,347 women: 16,608 with a uterus and 10,739 with prior hysterectomy.

What hormones did the WHI test?

It tested oral conjugated equine estrogens at 0.625 mg/day plus medroxyprogesterone acetate at 2.5 mg/day in women with a uterus, and oral conjugated equine estrogens at 0.625 mg/day alone in women with prior hysterectomy.

Did the WHI find that hormone therapy causes breast cancer?

The answer depends on the regimen and population. In the CEE-plus-MPA trial, invasive breast cancer incidence was higher with long-term follow-up: HR 1.28 (95% CI 1.13–1.45). In the CEE-alone trial among women with prior hysterectomy, incidence was lower: HR 0.78 (0.65–0.93), and breast cancer mortality was lower: HR 0.60 (0.37–0.97). Those are different randomized regimens in different populations and should not be reported as one result.

Was the Women's Health Initiative defunded in 2025?

WHI announced on April 21, 2025 that four Regional Center contracts would not be renewed. It said on April 25 that it had received no NIH confirmation of reported reversal. On May 6, WHI reported that its NIH acquisitions officer had confirmed the nonrenewal decision was rescinded.

Why did FDA change hormone-therapy labels in 2025 and 2026?

FDA said its later literature review, drug-utilization review, public input and July 2025 expert panel supported labeling that better distinguished age, timing, formulation and indication. It requested changes on November 10, 2025 and approved the first six revised product labels on February 12, 2026. The decision remains contested, and the WHI itself took no position on the boxed-warning action.

Is the WHI's own timeline up to date?

The dated “Journey through WHI's history” chronology on the WHI About page ended with Long Life Study 2 in 2023 when checked August 3, 2026. Separate WHI news pages contain the 2025 funding and FDA-response records, so the website as a whole contains newer material even though that single chronology does not.

How to cite this page

The reference below fixes the page title, publisher, version and verification date so the dataset can be identified without ambiguity. It is neutral attribution information, not a request for a citation.

These details identify the title, publisher, dataset version and verification date. They do not condition access or reuse on attribution.

The HRT Index Editorial Team. “Women's Health Initiative Timeline
(1991–2026): Every Key Date, Trial and Finding.”
The HRT Index Research & Reference. Version 1.0.
Last verified August 3, 2026.
https://thehrtindex.com/research/womens-health-initiative-timeline/

The tables are rendered as plain HTML on the published page. Each table carries a visible source line identifying the primary records used and the verification date.

Primary sources

Every consequential date, number and clinical result on this page traces to an official WHI, NIH/NHLBI or FDA record, a trial registry, or an original peer-reviewed WHI publication. Secondary commentary is included only where the commentary itself is the dated event being documented.

Women's Health Initiative, NIH and NHLBI

• Women's Health Initiative. About WHI — program chronology, study organization and dated milestones
• Women's Health Initiative. Main Findings from the WHI Trials — principal-publication index
• Women's Health Initiative. WHI Extension Studies — extension-study enrollment and phase descriptions
• Women's Health Initiative. WHI Funding Announcement — April 21, April 25 and May 6, 2025 updates
• Women's Health Initiative. WHI response to FDA hormone-label changes — November 12, 2025 statement and later updates
• National Heart, Lung, and Blood Institute. Women's Health Initiative — program design, original-study completion and current extension status
• ClinicalTrials.gov. NCT00000611
• Fred Hutchinson Cancer Center. NHLBI Stops Trial of Combined Hormone-Replacement Therapy, July 9, 2002

Principal randomized-trial and follow-up reports

• Writing Group for the Women's Health Initiative Investigators. Risks and Benefits of Estrogen Plus Progestin in Healthy Postmenopausal Women. JAMA. 2002;288(3):321–333. doi:10.1001/jama.288.3.321
• Shumaker SA, Legault C, Rapp SR, et al. Estrogen Plus Progestin and the Incidence of Dementia and Mild Cognitive Impairment. JAMA. 2003;289(20):2651–2662. doi:10.1001/jama.289.20.2651
• Anderson GL, Limacher M, Assaf AR, et al. Effects of Conjugated Equine Estrogen in Postmenopausal Women With Hysterectomy. JAMA. 2004;291(14):1701–1712. doi:10.1001/jama.291.14.1701
• Shumaker SA, Legault C, Kuller L, et al. Conjugated Equine Estrogens and Incidence of Probable Dementia and Mild Cognitive Impairment. JAMA. 2004;291(24):2947–2958. doi:10.1001/jama.291.24.2947
• Prentice RL, Caan B, Chlebowski RT, et al. Low-Fat Dietary Pattern and Risk of Invasive Breast Cancer. JAMA. 2006;295(6):629–642. doi:10.1001/jama.295.6.629
• Beresford SAA, Johnson KC, Ritenbaugh C, et al. Low-Fat Dietary Pattern and Risk of Colorectal Cancer. JAMA. 2006;295(6):643–654. doi:10.1001/jama.295.6.643
• Howard BV, Van Horn L, Hsia J, et al. Low-Fat Dietary Pattern and Risk of Cardiovascular Disease. JAMA. 2006;295(6):655–666. doi:10.1001/jama.295.6.655
• Jackson RD, LaCroix AZ, Gass M, et al. Calcium plus Vitamin D Supplementation and the Risk of Fractures. N Engl J Med. 2006;354:669–683. doi:10.1056/NEJMoa055218
• Wactawski-Wende J, Kotchen JM, Anderson GL, et al. Calcium plus Vitamin D Supplementation and the Risk of Colorectal Cancer. N Engl J Med. 2006;354:684–696. doi:10.1056/NEJMoa055222
• Stefanick ML, Anderson GL, Margolis KL, et al. Effects of Conjugated Equine Estrogens on Breast Cancer and Mammography Screening. JAMA. 2006;295(14):1647–1657. doi:10.1001/jama.295.14.1647
• Rossouw JE, Prentice RL, Manson JE, et al. Postmenopausal Hormone Therapy and Risk of Cardiovascular Disease by Age and Years Since Menopause. JAMA. 2007;297(13):1465–1477. doi:10.1001/jama.297.13.1465. Correction: JAMA. 2008;299(12):1426
• LaCroix AZ, Chlebowski RT, Manson JE, et al. Health Outcomes After Stopping Conjugated Equine Estrogens. JAMA. 2011;305(13):1305–1314. doi:10.1001/jama.2011.382
• Manson JE, Chlebowski RT, Stefanick ML, et al. Menopausal Hormone Therapy and Health Outcomes During the Intervention and Extended Poststopping Phases. JAMA. 2013;310(13):1353–1368. doi:10.1001/jama.2013.278040
• Roth JA, Etzioni R, Waters TM, et al. Economic Return From the Women's Health Initiative Estrogen Plus Progestin Clinical Trial. Ann Intern Med. 2014;160(9):594–602. doi:10.7326/M13-2348
• Manson JE, Aragaki AK, Rossouw JE, et al. Menopausal Hormone Therapy and Long-term All-Cause and Cause-Specific Mortality. JAMA. 2017;318(10):927–938. doi:10.1001/jama.2017.11217
• Manson JE, Aragaki AK, Bassuk SS, et al. Menopausal Estrogen-Alone Therapy and Health Outcomes in Women With and Without Bilateral Oophorectomy. Ann Intern Med. 2019;171(6):406–414. doi:10.7326/M19-0274
• Chlebowski RT, Anderson GL, Aragaki AK, et al. Association of Menopausal Hormone Therapy With Breast Cancer Incidence and Mortality During Long-term Follow-up. JAMA. 2020;324(4):369–380. doi:10.1001/jama.2020.9482
• Manson JE, Crandall CJ, Rossouw JE, et al. The Women's Health Initiative Randomized Trials and Clinical Practice: A Review. JAMA. 2024;331(20):1748–1760. doi:10.1001/jama.2024.6542
• Rossouw JE, Aragaki AK, Manson JE, et al. Menopausal Hormone Therapy and Cardiovascular Diseases in Women With Vasomotor Symptoms. JAMA Intern Med. 2025;185(11):1330–1339. doi:10.1001/jamainternmed.2025.4510. Published online September 15, 2025; subsequently corrected online

FDA and published regulatory positions

• FDA. FDA Expert Panel on Menopause and Hormone Replacement Therapy for Women, July 17, 2025
• FDA. FDA Requests Labeling Changes Related to Safety Information to Clarify the Benefit/Risk Considerations for Menopausal Hormone Therapies, November 10, 2025
• Makary MA, Nguyen T, Høeg TB, Tidmarsh GF. Updated Labeling for Menopausal Hormone Therapy. JAMA. doi:10.1001/jama.2025.22259
• FDA. FDA Approves Labeling Changes to Menopausal Hormone Therapy Products, February 12, 2026
• FDA. Menopausal Hormone Therapies With Updated Prescribing Information
• Wittes J, Braunwald E, Chesney MA, et al. Menopausal Hormone Labels Should Rely on Evidence, Not Opinion. JAMA. 2026;335(14):1201–1202. doi:10.1001/jama.2026.1308
• Cunningham RL, Galea LAM, Goulmamine S, et al. Advancing Evidence-Based Regulation. Biol Sex Differ. 2026;17:30

Version history

Version 1.0 is the first public release of the normalized chronology and its supporting evidence tables. Later versions should name the rows changed, the source that prompted the change, and the date each current-status claim was rechecked.

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