18 september 2009

Smoking and heart disease risks can cut life span by 10 years

Cigarette smoke by Tomasz Sienicki via Wikimedia Commons
Men who smoke, have high blood pressure and raised cholesterol at age 50 can expect to live 10 years less than those without these risk factors.

Middle aged men who smoke, have high blood pressure and raised cholesterol levels can expect a 10–15 year shorter life expectancy from age 50 compared with men without these risk factors.

The Oxford University study published in the BMJ reports data from the Whitehall study, in which the health of 19,000 male civil servants has been followed for almost 40 years since 1970, when they were aged 40–69.

'We’ve shown that men at age 50 who smoke, have high blood pressure and high cholesterol levels can expect to survive to 74 years of age, while those who have none of these risk factors can expect to live until 83,’ says Dr Robert Clarke of the Clinical Trial Service Unit at the University of Oxford, who led the research team.

'We’ve been able to refine this further by computing a risk score for each study participant that also includes body mass index and diabetes as well as these three risk factors. Looking at those at the extremes, we find that the 5% with the highest risk scores have a 15 year reduced life expectancy compared to the 5% with the lowest scores.

Death rates from heart disease, and to a lesser extent from other diseases, have steadily declined in the UK since the early 1970s, resulting in substantial improvements in life expectancy. The longer life spans are believed to result from stopping smoking, changes in diet and lifestyle, and better treatment for people with vascular disease. But previous studies have not been able to investigate the extent to which the differences in life expectancy can be explained by differences in cardiovascular risk factors.  

If you stop smoking or take measures to deal with high blood pressure or body weight, it will translate into increased life expectancy.

Dr Robert Clarke

‘The Whitehall study was set up in 1970 at the peak of a heart disease epidemic in the UK to look at the effects of smoking, blood pressure and cholesterol levels,’ explains Dr Clarke. Since that time, researchers have followed what’s happened to the 19,000 civil servants through middle age and old age over a period of 38 years.

'It is precisely this kind of very prolonged follow-up study that is necessary to get these results – that modest differences in heart risk factors can accurately predict significant differences in life expectancy,’ he adds.

Participants completed a questionnaire at entry in 1970 about previous medical history, smoking habits, employment grade and marital status. The initial examination recorded height, weight, blood pressure, lung function and blood cholesterol and glucose levels.

With funding from the British Heart Foundation, the records of 18,863 men were traced and 7,044 surviving participants were re-examined in 1997 (about 28 years after their initial examination).

Dr Clarke says: ‘The results give people another way of looking at heart disease risk factors that can be understood more readily. If you stop smoking or take measures to deal with high blood pressure or body weight, it will translate into increased life expectancy.

'It also provides support for existing public health policies. Bans on smoking in public places, efforts to lower saturated fats and salt, combined with medications for those at high risk of cardiovascular disease, when taken together will result in substantial improvements in life expectancy across the population.’

Image credit: Cigarette smoke by Tomasz Sienicki via Wikimedia Commons