The Association Between Blood Pressure and Years of Schooling Versus Educational Credentials: Test of the Sheepskin Effect

Purpose: Attaining a degree may offer greater opportunities for health than years of schooling alone. This study examines whether there is a degree, or " sheepskin," effect on the association between education and blood pressure. Methods: Multivariable-adjusted ordinal and linear regression models assessed associations of years of schooling and degree attainment with systolic and diastolic blood pressure in a sample of 552 adults ages 38 to 47 years. Results: Years of schooling was inversely associated with systolic blood pressure adjusting for age, gender and race (β = -0.4, 95% confidence limit: -0.7, -0.1 mmHg systolic blood pressure/year of schooling). Additional adjustment for mother's education, childhood verbal intelligence quotient, childhood health, and childhood socioeconomic status had minimal impact on effect size (β = -0.3, 95% confidence limit = -0.7, 0.0). However, years of schooling was no longer associated with blood pressure in the fully adjusted model which included additional adjustment for degree attained (β = 0.0, 95% confidence limit: -0.5, 0.4). In the fully adjusted model (including adjustment for years of schooling), individuals with a graduate degree still had significantly lower systolic blood pressure than HS degree-holders (e.g., β = -9.2, 95% confidence limit: -15.2, -3.2 for graduate vs high school degree). Findings were similar for diastolic blood pressure. Conclusions: The association of years of schooling with blood pressure may be largely due to degree attainment rather than simply the knowledge and skills accumulated due to years of schooling alone.