Stroke Risk Factors
A number of risk factors have been established for the occurrence of stroke. In general, risk factors for stroke are similar to those for Coronary Heart Disease (Mackay et al. 2004). Literatures have categorized stroke risk factors into non-modifiable factors and modifiable factors. Non-modifiable risk factors include age, gender, ethnicity and heredity. The chance of having a stroke increases with age (Stokes 2004) and stroke risk doubles every decade after age 55 years (Mackay et al. 2004), however stroke is not a natural concomitant of increasing age (Warlow et al. 2001). Men are at higher risk for stroke than women at all ages until around 55 years (Ariesen et al. 2003). In terms of ethnicity, increased risk of stroke is noted for the Blacks, Chinese, some Hispanic, American and Japanese (Mackay et al. 2004). There is also increased risk of stroke if a first degree blood relative has stroke before the age of 55 years (in male relative) or 65 years (in female relative) (Mackay et al. 2004).
Three most important modifiable risk factors are hypertension, high cholesterol and low fruit and vegetable intake (Mackay et al. 2004). Hypertension, including borderline hypertension, is the leading risk factor based on the degree of risk and prevalence (Sacco et al. 1999). The risk of stroke increases continuously above blood pressure levels of approximately 115/75 mm Hg (Lawes et al. 2004). Sub-optimal systolic blood pressure above 115 mm Hg contributes about 65% in the risk of stroke in the world population (Mackay et al. 2004). Treatment of hypertension reduces risk of stroke by 40% and for every 10 people who die of stroke, 4 could have been saved if their blood pressure have been regulated (Mackay et al. 2004). High cholesterol contributes approximately 18% to the risk of stroke world wide (Mackay et al. 2004). Overall, each 1-mmol/l higher level of total cholesterol was associated with 25% increased risk of fatal or non-fatal ischaemic stroke (Asia Pacific Cohort Studies Collaboration 2003). About 11% of stroke in the world population is caused by low fruit and vegetables intake (Mackay et al. 2004). Other modifiable risk factors include cigarette smoking (increase stroke risk by 100%) (Warlow 2001, Mackay et al. 2004), physical inactivity (increase risk by 50% or 1.5 times higher) (Mackay et al. 2004), diabetes mellitus (Warlow 2001), atrial fibrillation, carotid stenosis (The American Heart Association (AHA) 2002; Ariesen et al. 2003), previous stroke (Mackay et al. 2004) and psychological stress (Truelsen et al. 2003).