More secondary education improves health in middle age by reducing body fat and the prevalence of lung conditions, but it also worsens health by increasing blood pressure. These are the central findings of research by Silvia Helena Barcellos, Leandro Carvalho and Patrick Turley, to be presented at the Royal Economic Society''s annual conference at the University of Bristol in April 2017.
The authors analyse a 1972 policy change in England, Wales and Scotland that increased the minimum age at which students could leave school from 15 to 16 years old. Using data from the UK Biobank, which has measured the body size, lung capacity and blood pressure of more than half a million 40-69 year olds living in the UK, they find that obesity rates in adults who were affected by this change decreased by 31%, with the reduction in body fat happening most among those who are most unhealthy.
The authors comment: ''A social policy may not be unequivocally good or bad for health. It may improve some aspects of health while worsening others – and of course, the effects of education on health vary across people.''
They add: ''Even though our study finds that education increases average blood pressure, these increases are not too concerning because there is no change in the prevalence of high blood pressure.
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More secondary education improves health in middle age by reducing body fat and lung conditions, but it also worsens health by increasing blood pressure. That is the central finding of this research.
The study analyses a policy change in England, Wales and Scotland that increased the minimum age at which students could leave school from 15 to 16 years old. It finds that the reductions in body fat caused by this extra education occur where they matter the most: obesity rates decrease by 31%. In contrast, the increases in blood pressure may not be too concerning because education does not affect the prevalence of high blood pressure.
The study shows that a social policy may not be unequivocally good or bad for health. It may improve some aspects of health while worsening others. It also highlights how the effects of education on health vary across people.
In the past, data limitations forced researchers to study the effect of education on average health. The focus on the effect on average health may give the false impression that everyone is affected the same way. In reality, the effects of education on health may vary across people in the same way that the effectiveness of medical treatments varies across people.
The researchers study the effects of education on health by exploring changes in compulsory schooling. In 1972, England, Scotland and Wales made it compulsory for students to stay in school until age 16. The law stipulated that students born on or after 1 September 1957 had to stay until age 16 while students born before that date could drop out at age 15.
Figure 1 illustrates the effect of the 1972 school leaving age reform on education. The circles show the fraction of individuals staying in school until age 16 by date of birth. The vertical dashed line marks the first cohort affected by the reform formed by those born between September 1957 and August 1958. Students to the left of the line could drop out at age 15 while students born to the right were forced to stay in school until age 16.
The policy generates a unique relationship between the fraction staying in school until age 16 and date of birth. The fraction was increasing for younger cohorts born before September 1957, but then it sharply increased exactly when the policy kicked in. That is because the reform forced some students born after 1 September 1957 to remain in school an extra year, generating a difference in the overall education of those born right after September 1957 and those born right before.
The researchers investigate whether education affects health by examining if there is a corresponding difference in the health of those born right after September 1957 and those born right before. In practice, they study whether there is a similar pattern between health and date of birth with health measures changing abruptly exactly when the policy kicked in.
The study uses data from the UK Biobank, which between 2006 and 2010, measured the body size, lung capacity and blood pressure of more than half a million 40-69 year olds living in the UK.
The researchers find that those born after September 1957 have lower body fat and fewer lung conditions than those born before that date, but they also have higher blood pressure. Education improves the first two aspects of health while worsening the third.
The reduction in body fat happens among those who are most unhealthy.
Figure 2 shows a substantial reduction in obesity rates exactly when the school leaving age reform kicked in. The authors estimate that the policy reduced obesity by 31% among those forced to stay in school one more year.
By comparison, Figure 3 shows the policy had no effect on the fraction of study participants classified as overweight. The contrast of the two figures highlights how different people were affected differently by the policy.
Even though the study finds that education increases average blood pressure, these increases are not too concerning because there is no change in the prevalence of high blood pressure. Figure 4 shows that the fraction of individuals with high blood pressure barely changed when the school leaving age reform kicked in.
In a follow-up study, the authors are investigating why the effects of education on health vary across people. They are examining whether genetic factors determine the extent to which one''s health is affected by education, investigating for example whether the effects on body fat depend on one''s genetic risk for obesity or whether the effects on blood pressure depend on one''s genetic risk for hypertension.
