To quantify the magnitude and direction of the effect sizes of key modifiable risk factors of stroke according to three age groups: <50years(young), 50-65 years(middle age) and >65 years(elderly) in West Africa. 

Age is a non-modifiable risk factor for stroke occurrence due its influence on vascular risk factor acquisition. In sub-Saharan Africa, the effect sizes of vascular risk factors for stroke occurrence by age is unknown. 

The Stroke Investigative Research and ºÃÉ«ÏÈÉúal Network (SIREN) is a multicenter, case-control study involving 15 sites in Ghana and Nigeria. Cases include adults aged ≥18 years with evidence of an acute stroke. Controls were age-and-gender matched stroke-free adults. Detailed evaluations for vascular, lifestyle, stroke severity and outcomes were performed. We used conditional logistic regression to estimate adjusted odds ratios (aOR) of vascular risk factors of stroke. 

Among 3,553 stroke cases, 813(22.9%) were young, 1441(40.6%) were middle-aged and 1299(36.6%) were elderly. Five modifiable risk factors were consistently associated with stroke occurrence regardless of age namely hypertension, dyslipidemia, diabetes mellitus, regular meat consumption and non-consumption of green vegetables. Among the 5 co-shared risk factors, the effect size, aOR(95%CI) of dyslipidemia, 4.13(2.64-6.46), was highest among the young age group, hypertension, 28.93(15.10-55.44) and non-consumption of vegetables 2.34(1.70-3.23) was highest among the middle-age group while diabetes, aOR of 3.50(2.48-4.95) and meat consumption, 2.40(1.76-3.26) were highest among the elderly age group. Additionally, among the young, middle-age and elderly age group, cigarette smoking, physical inactivity and cardiac disease were associated with stroke respectively. 

Age has a profound influence on the profile, magnitude and direction of effect sizes of vascular risk factors for stroke occurrence among West Africans. Population-level prevention of stroke must target both co-shared dominant risk factors as well as factors that are unique to specific age bands in Africa.