Researchers who analyzed 20 years worth of data conclude that a "substantial" proportion of high blood pressure cases are associated with a lack of physical activity and not enough aerobic fitness.
There is a difference in measuring aerobic fitness and physical activity, according to scientists at Northwestern University's Feinberg School of Medicine.
Physical activity is a behavior, while aerobic fitness is a physiological measure that reflects a combination of physical activity, genetic potential, and functional health of various organs.
The researchers examined data on 4,618 men and women taking part in a research project called the Coronary Artery Risk Development in Young Adults Study, or CARDIA.
Study researcher Mercedes Carnethon, PhD, an assistant professor of preventive medicine at Northwestern, says the study confirms earlier research pointing to a link between fitness and hypertension "by showing that fitness during young adulthood -- a time when cardiovascular disease risk burden is typically low -- is an important indicator of hypertension development in middle age."
Carnethon says in a news release that high blood pressure is known to develop over a long period of time and is due to a combination of factors that includes genetics, diet, and health behaviors.
"Our study measures a comprehensive set of these health risk factors over 20 years, making this one of the longest follow-up studies to test whether activity and fitness are associated with hypertension development," she says.
The researchers measured blood pressure and estimated fitness levels based on the duration of exercise treadmill tests conducted on people who were between 18 and 30 in 1985.
Participants were re-examined after two, five, seven, 10, 15, and 20 years.
Activity was assessed by an interviewer who administered a self-reported questionnaire.
Researchers say low fitness has a stronger link with the development of hypertension than low-reported physical activity, though the two appear to have independent effects.
Researchers also found that:
Hypertension incidence was 13.8% per 1,000 person-years, a calculation found by taking the number of new cases within a specified time period divided by the size of the population initially at risk.
Low fitness was associated with an increased risk of developing high blood pressure after adjusting for smoking, age, sex, cholesterol, race, diet, and other factors.
The estimated proportion of high blood pressure that could be prevented if participants moved to a higher fitness category was 34%. This figure is called the "preventive fraction," which tells scientists, at least hypothetically, what proportion of disease could be eliminated if the risk factor were removed from the studied population.
Clinical trials with various activity and fitness levels are needed before doctors can use the study information to make recommendations about the amount of physical activity needed to improve fitness and lower the risk of developing hypertension, the researchers say.
The study is published in the journal Hypertension.