New research offers a compelling case for staying in school: American adults who spent more time in the classroom as kids have a lower risk of heart disease.
"As a society, we should be thinking about investing in social policies to improve overall health and reduce health care costs," said study author Dr. Rita Hamad. She's an assistant professor of family and community medicine at the University of California, San Francisco.
Hamad and her team analyzed data gathered between 1971 and 2012 from more than 75,000 people born during the first half of the 20th century. During that time, states required children to attend school for as many as 12 years.
About one-third of participants did not graduate from high school and 34.5% reported heart disease.
But each year of compulsory schooling through high school was associated with a 2.5% reduction in heart disease and in risk factors for heart disease -- including a more than 3% reduction in smoking and a nearly 5% lower risk of depression. Only an association, rather than a cause-and-effect link, was seen by researchers.
"For clinicians and health systems struggling to address disparities in heart disease between the rich and the poor, our findings suggest that cross-sectoral interventions to address social factors like education are important," Hamad said in a university news release.
The study offers some of the first evidence of the effects of education policies on heart disease in the United States, according to the researchers.
While more education was associated with improved "good" high-density lipoprotein (HDL) cholesterol, it was also linked to higher total cholesterol and body mass index (BMI). BMI is an estimate of body fat based on weight and height.
One possible explanation is that high-income people born between 1900 and 1950 tended to eat richer diets. Higher BMI today is more closely associated with lower incomes, according to the researchers.
"Overall, people with more education may have reduced heart disease because they have higher incomes, allowing them to afford better food and health care," Hamad said. "Or, it may be that they have more resources and therefore less stress, which has been previously linked with heart disease."
The researchers are now examining how policies on school attendance affect health care costs and whether the policies reduce racial disparities in heart disease.
The study was published online June 25 in the journal PLOS Medicine.
The U.S. National Heart, Lung, and Blood Institute offers a guide to a healthy heart.