Modifiable lifestyle factors
Smoking
Smoking is the most important lifestyle risk factor. Smoking almost doubles a person’s risk of ischaemic stroke, independent of other risk factors. It increases the risk of sub-arachnoid haemorrhage by 3.5 times that of a non-smoker.
Smoking is directly responsible for a greater percentage of strokes in younger adults. In older adults, hypertension, heart disease and diabetes account for more of the total. Heavy smokers are at greater risk than light smokers.
The relative risk of stroke decreases immediately after stopping smoking, and after 2 to 4 years there is a major reduction in risk. It may however take several decades for the risk to drop to the level of someone who has never smoked.
High alcohol consumption
The medically recommended maximum weekly intake of alcohol is 21 units for men and 14 for women. This equates to an approximate daily limit of 3 units for men and 2 units for women as it is not recommended that the weekly allowance is consumed over one or two days. A unit of alcohol is 10 ml (1 cl) by volume, or 8 g by weight, of pure alcohol. For example:
One unit of alcohol is about equal to:
- Half a pint of ordinary strength beer, lager, or cider (3–4% alcohol by volume)
OR
- A small pub measure (25 ml) of spirits (40% alcohol by volume)
OR
- A standard pub measure (50 ml) of fortified wine such as sherry or port (20% alcohol by volume).
There are one and a half units of alcohol in:
- A small glass (125 ml) of ordinary strength wine (12% alcohol by volume),
OR
- A standard pub measure (35 ml) of spirits (40% alcohol by volume).
Generally, an increase in alcohol consumption leads to an increase in blood pressure. Heavy drinking is associated with an increased risk of both ischaemic stroke and haemorrhagic stroke, this can also lead to cardiac dysrhythmia, even in young people. This could cause an embolic stroke. Daily consumption of smaller amounts of alcohol however, has been shown to have a protective effect against ischaemic stroke.
It is thought that moderate alcohol consumption may act in the same way as aspirin by decreasing blood clotting, but heavy consumption may significantly decrease platelet numbers and compromise the ability of the blood to clot thus leading to haemorrhage.
Heavy binge drinking can lead to a rebound effect where platelet numbers dramatically increase after drinking stops, with an increased risk of ischaemic stroke. Binge drinking increases the risk of stroke 5 times. Binge drinking is generally defined as men consuming at least eight, and women at least six units of alcohol in a single day.
Obesity
Obesity, defined as a Body Mass Index (BMI) of 30 or over, carries a risk of stroke double that of non-obese people. This is particularly where body fat is situated in the abdominal region rather than on the hips and thighs.
Body Mass Index (BMI) is a relationship between weight and height that is associated with body fat and health risk.
The equation is BMI = body weight in kilograms/height in meters squared.
Being overweight is also associated with high blood cholesterol levels and hypertension, although the precise mechanism by which obesity is linked to strokes remains unclear.
Physical inactivity
An inactive lifestyle increases the risk of stroke to double that of an active person. To achieve an active lifestyle, adults should aim for 30 minutes of moderate physical activity on most days of the week. Moderate activity equates with brisk walking, cycling or swimming. The 30 minutes need not be undertaken in one go, but may be divided into three 10-minute slots.
