The Perindopril Protection Against Recurrent Stroke Study (PROGRESS) was a landmark clinical trial aimed at evaluating the effects of blood pressure reduction on the risk of recurrent stroke in individuals with a history of stroke or transient ischemic attack (TIA). 

**Study Design and Participants:**

- **Population:** The trial enrolled 6,105 participants from 172 centers across Asia, Australasia, and Europe. All participants had experienced a stroke or TIA within the previous five years.

- **Intervention:** Participants were randomly assigned to receive either active treatment or a placebo. The active treatment consisted of the angiotensin-converting enzyme (ACE) inhibitor perindopril (4 mg daily), with the addition of the diuretic indapamide at the discretion of the treating physicians.

- **Follow-Up:** The average follow-up period was four years.

**Key Findings:**

- **Blood Pressure Reduction:** The active treatment group experienced an average blood pressure reduction of 9/4 mm Hg.

- **Stroke Risk Reduction:** There was a significant reduction in the incidence of stroke among those receiving active treatment compared to the placebo group (10% vs. 14%), representing a relative risk reduction of 28% (95% CI: 17–38; p<0.0001).

- **Combination vs. Single Therapy:** Participants receiving the combination of perindopril and indapamide had a greater reduction in blood pressure (12/5 mm Hg) and a more substantial decrease in stroke risk (43% reduction) compared to those on perindopril alone, who did not exhibit a discernible reduction in stroke risk. 

**Conclusions:**
The PROGRESS trial demonstrated that a blood pressure-lowering regimen, particularly the combination of perindopril and [[indapamide]], significantly reduces the risk of recurrent stroke in individuals with a history of cerebrovascular events. These benefits were observed regardless of the participants' baseline blood pressure levels, suggesting that such a treatment approach should be considered for all patients with a history of stroke or TIA, irrespective of their initial blood pressure.