Effect of lifestyle on death and disease

We are more concerned these days with living a long and healthy life, rather than just living longer. Many studies have examined the effects of lifestyle on the risk of disease, but typically, they focus on one specific behaviour, e.g. exercise, in relation to one outcome, e.g. coronary heart disease. Individuals often follow a lifestyle pattern however, which combines more than one behaviour. This paper examines the combined effect of several lifestyle factors not only on survival, but surviving 15 years free of major cardiovascular problems and diabetes.

Message

A 50 year old man has an 89% chance of surviving to 65 without developing coronary heart disease, stroke or diabetes if he has never smoked, is physically active and not overweight. On the other hand, if he smokes, is inactive and very overweight he only has a 42% chance.

Reference

SG Wannamethee et al. Lifestyle and 15-year survival free of heart attack, stroke, and diabetes in middle-aged British men. Archives of Internal Medicine 1998 158: 2433-2440.

Study

Participants were 7,142 men, aged 40-59 years, from the British Regional Heart Study. The men were from one general practice in each of 24 towns in England, Wales and Scotland and were representative of the social class distribution of middle-aged men in Great Britain (using the Registrar General's classification). Questionnaires obtained information on smoking habits, alcohol intake, physical activity and medical history. Physical measurements, including height and weight, were also taken. The men had no history of coronary heart disease, diabetes or stroke at the start of the study in 1978.

The lifestyle factors were defined/classified as follows:

Body mass index: an index of weight adjusted for height, classified by the World Health Organisation as: normal 18.5 to 24.9; grade 1 overweight 25.0 to 29.9; grade 2 overweight 30.0 to 39.9; and grade 3 overweight 40.0 or higher.
Current smoking status: never, former and current smokers.
Alcohol intake: one drink is defined as a glass of wine or tot of spirit or half a pint of beer (one drink = 8-10g of alcohol).
Physical activity: an exercise score was derived based on the frequency and type (intensity) of physical activity which included walking, cycling, recreational activity (e.g. gardening) and vigorous sport (e.g. running, swimming).

The outcomes measured were death from any cause or surviving free of a heart attack, stroke or non-insulin-dependent diabetes mellitus during the follow-up period of 15 years. Evidence of nonfatal heart attacks, strokes and diabetes were obtained from the general practitioners every two years.

During the 15 years of follow-up there were 1,064 deaths from all causes, 770 major heart attacks, 247 strokes and 252 cases of diabetes.

Results

Lifestyle and death or risk of having a heart attack, stroke or diabetes

The risk of death or heart attack, stroke or diabetes rose with increasing smoking levels. Heavy smokers (smoking more than 21 cigarettes a day) were two and a half times more likely to die or have a heart attack, stroke or diabetes than non-smokers (relative risk 2.50, 95% confidence interval 2.12 to 2.94).

Having a body mass index of 26 or higher increased the risk of death or heart attack, stroke or diabetes. A body mass index of 26-27.9 increased the risk by 28%; the risk doubled with a body mass index of more than 30, compared with an index of 20-21.9 (relative risks 1.42 and 2.11, 95% confidence intervals 1.06 to 1.56, 95% confidence intervals 1.71 to 2.62).

All levels of exercise reduced the risk of death or heart attack, stroke or diabetes. The optimum was a moderate level which reduced the risk by 40% (relative risk 0.60, 95% confidence interval 0.50 to 0.72).

Compared with an occasional intake of alcohol (less than one drink a week), no alcohol increased the risk of death, heart attack, stroke or diabetes by 24% and light consumption (1-15 drinks a week) reduced the risk by 16% (relative risks 1.24 and 0.84, 95% confidence intervals 1.02 to 1.52 and 0.74 to 0.96).

These results were adjusted for age and each of the other lifestyle factors.

Lifestyle and surviving 15 years free of coronary heart disease, stroke or diabetes

Table 1 shows the probability of surviving 15 years free of coronary heart disease, stroke and diabetes in a man aged 50 years for various combinations of smoking status, physical activity and body mass index. Alcohol intake was not included.

Table 1: Probability of 15-year survival without coronary heart disease, stroke, and diabetes in a man aged 50 years with selected combinations of risk factors
	BMI 20-24

The probability ranged from 89% in an active man with a body mass index between 20 and 24 who had never smoked to 42% in an inactive smoker with a body mass index of 30 or higher. It actually becomes more rather than less likely that the obese inactive smoker will have a major health problem.

Comments

This study demonstrates the substantial difference we can make to our health: smoking, exercise and weight control are behaviours we can change.

The estimates were based on measurements taken at the beginning of the study and do not take into account changes made in later life, during the 15-year follow-up period. Positive lifestyle changes will reduce risk of mortality and disease and it is never too late in life to make them. They are worth making for everyone, but those people with lifestyles that include a combination or risk factors will benefit particularly.

BMI 28-30		BMI 30+
	Active	Inactive	Active	Inactive	Active	Inactive
Never smoked	89	83	85	77	78	67
Former smokers	86	78	81	71	72	59
Current smokers	77	67	70	56	58	42