by Lisa Nainggolan
Oxford, UK - A new analysis from the British Whitehall study looking at male civil servants has found that a single measurement of three cardiovascular risk factors in middle age—smoking, high blood pressure, and high cholesterol—predicted a threefold higher rate of vascular mortality compared with none of the risk factors . The researchers also showed a twofold higher rate of nonvascular mortality and an almost 10-year shorter life expectancy from age 50 in those with the risk factors.
Dr Robert Clarke (University of Oxford, UK) and colleagues report their findings online September 17, 2009 in BMJ. And when they used more extreme categorization of risk factors, including body-mass index (BMI), diabetes mellitus/glucose intolerance, and employment grade, life expectancy differed by up to 15 years.
Clarke says there has been uncertainty about the limits of life expectancy and the relevance of cardiovascular risk factors for its prediction. "What is unique about this study is the prolonged follow-up; it enables us to put a figure on the life-limiting effects of these risk factors," he told heartwire.
The study shows concordance with recent findings from the Physicians' Health Study in the US  and "provides a stark illustration of the importance of these risk factors to reduce life expectancy," he adds. The findings also provide support for public-health policies aimed at achieving modest changes in major risk factors throughout the population to achieve improvements, he notes.
"This is a metric that is readily understood by patients. It's repackaging these old risk factors to give them a bit more quantitative importance. We have all these new factors, like CRP, when in fact these old risk factors explain much of the difference in life expectancy," he stresses.
All three risk factors associated with 10 to 15 years lower life expectancy
Data were collected from 18 863 men aged 40 to 69 who were working in the civil service in London when they were first examined in 1967-1970. They completed questionnaires and had a medical exam, including measurement of blood pressure, cholesterol, glucose concentrations, and height and weight, and answered questions about medical history, smoking habits, employment grades, and marital status.
People were divided into two groups based on the three main CV risk factors: current smoker (yes/no); baseline BP ("high"=systolic BP >140 mm Hg or "low"; and baseline cholesterol ("high"=cholesterol >5.0 mmol/L or "low"). In addition, a risk score was computed from these factors. The men were followed for 38 years: 13 501 died, and 4811 were reexamined in 1997.
At entry, 42% of the men were current smokers, 39% had high blood pressure, and 51% had high cholesterol. At the reexamination, about two-thirds of the previously "current" smokers had quit smoking shortly after entry, and the mean differences in levels of those with high and low levels of BP and cholesterol were attenuated by two-thirds.
Despite this, compared with men without any baseline risk factors, the presence of all three risk factors at entry was associated with a 10-year shorter life expectancy from age 50 (23.7 vs 33.3 years). And compared with men in the lowest 5% of the risk score based on smoking, diabetes, employment grade, and continuous levels of BP, cholesterol concentration, and BMI, men in the highest 5% had a 15-year shorter life expectancy from age 50 (20.2 vs 35.4 years).
Prospective study, with large sample size and long follow-up
The study has several strengths in addition to the prolonged follow-up, say Clarke et al, including a prospective design, large sample size, availability of repeat measurements between middle and old age, a large number or deaths, and virtually complete mortality follow-up.
Limitations include the fact that total cholesterol concentrations were employed rather than cholesterol fractions or apolipoproteins, which are much stronger predictors of vascular mortality than total cholesterol, they note. Also, the effects of BP and cholesterol on mortality might have been slightly underestimated because of increased use of aspirin, statins, and BP-lowering drugs during follow-up (in 1997, around a third of survey participants were taking aspirin and/or antihypertensives, although only 2% were taking statins).
"Continued public-health strategies to lower mean levels of the three main cardiovascular risk factors, together with more intensive medical treatment for 'high-risk' subgroups, including use of medication to lower blood pressure and cholesterol concentration, which have proven efficacy, could result in further improvements in life expectancy," they conclude.
Clarke R, Emberson J, Fletcher A, et al. Life expectancy in relation to cardiovascular risk factors: 38-yar follow-up of 19 000 men in the Whitehall study. BMJ 2009; DOI:10.1136/bmj.b3513. Available at: http://www.bmj.com.
Yates LB, Djoussé L, Kurth T, et al. Exceptional longevity in men: modifiable risk factors associated with survival and function up to age 90 years. Arch Intern Med 2009; 168: 284-290.