BACKGROUND: Stroke and transient ischemic attack confer greater risk of cognitive decline and dementia. AIMS: We used data from the Perindopril Protection Against Recurrent Stroke Study (PROGRESS), a blood pressure-lowering randomized controlled trial in stroke/transient ischemic attack. We evaluated overall and sex-specific differences in treatment effects for cognitive decline/dementia, as well as associations with vascular and stroke-specific predictors,considering death as a competing risk. METHODS: Multinomial logistic regression was used to estimate overall and sex-specific odds ratios (OR) (95% confidence intervals (CI)) for treatment effects and predictors associated with the risk of cognitive decline/dementia, and the women-to-men ratio of odds ratio (RORs). RESULTS: Over a median four years, 763 cognitive decline/dementia (30.9% women) were recorded in 5888 participants. Women had lower odds of cognitive decline/dementia than men (OR 0.78, 95%CI 0.63-0.95). Active treatment was associated with lower odds of cognitive decline/dementia (0.84, 0.72-0.98), with no evidence of sex difference. Higher education (0.96,0.94-0.98 (per year)) and baseline Mini-Mental State Examination (MMSE)) were associated with lower odds of cognitive decline/dementia (0.84,0.82-0.86 (per point higher)). Higher diastolic blood pressure (1.11,1.02-1.20 (per 10 mmHg)), low estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2) (1.27,1.03-1.58), and peripheral arterial disease (1.78,1.26-2.52) were associated with higher odds of cognitive decline/dementia. APOE varepsilon4 was not associated with cognitive decline/dementia (1.05 (0.85-1.30)). Low eGFR was more strongly associated with cognitive decline/dementia in women than men (RORs, 1.60 (1.03-2.48)). Diabetes was more strongly associated with men than women. CONCLUSIONS: Several risk factors were associated with cognitive decline/dementia in people with prior stroke/transient ischemic attack, with notable sex differences. Long-term cognitive sequelae of stroke should be considered to strengthen joint prevention strategies for stroke, cognitive decline, and dementia.Trial Registration: This trial was not registered because enrolment began before 1 July 2005.Read less <