It has long been known that people are at a much higher risk of developing heart disease if they smoke cigarettes, have high blood pressure, high total cholesterol levels, or diabetes. The number of people who smoke and the number of people who have these common risk factors have decreased in recent decades, which has led to an increase in life expectancy for many people. More people than ever are now living to over 80 years old, leading some people to question whether recording these risk factors in middle age is still relevant for predicting risk of death from heart disease or stroke in old age.
To find this out, the researchers looked at data collected from 19,019 male civil servants working in London between 1967 and 1970 who participated in the Whitehall study. The participants were aged between 40 and 69 years at enrolment. Using questionnaires and simple clinical measurements (blood pressure, height and weight) and collection of a blood sample (for cholesterol and blood sugar), the researchers were able to record risk factors for heart disease.
Surviving participants had a repeat survey conducted in 1997 where they provided data on levels of risk factors for heart disease in both middle and in old age. The study participants were then followed up for 50 years to determine when they eventually died and, if they had died, to record the date and cause of death.
Key findings:
- By 1 July 2000, 97% (17,673) of the participants had died. 22% of participants died before they were 70 years old, 51% had died before they were 80 years old, and 80% had died before they were 90 years old;
- Of the 17,673 participants who had died by 2000, 45% (7,944) died from heart disease or stroke;
- Participants who had the lowest number of risk factors for heart disease had a less than 1% risk of dying from heart disease within ten years, and a 31% risk of eventually dying from heart disease;
- Participants who had the highest number of risk factors for heart disease had a 10% risk of dying from heart disease within ten years, and a 61% risk of eventually dying from heart disease;
- Participants with the lowest number of risk factors lived for an average of 12 years longer after the age of 50 than those with the highest number of risk factors.
Professor Robert Clarke, Emeritus Professor of Epidemiology and Public Health Medicine at Oxford Population Health, said ‘The Whitehall study started during the peak of the epidemic of heart disease related deaths in the UK in the 1970s. The study afforded a unique opportunity to look at data collected over the course of a lifetime and was a precursor to studies such as the UK Biobank and the China Kadoorie Biobank, which are answering the most pressing health challenges today. The results of the Whitehall study demonstrate that smoking cigarettes, having high blood pressure and cholesterol, and diabetes are still putting people at risk of developing heart disease and premature death today. They provide support for current health policies that recommend stopping smoking, maintaining a healthy lifestyle, and lowering levels of blood pressure and cholesterol.’