The association between blood pressure and years of schooling versus educational credentials: Test of the sheepskin effect

Abstract

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 (beta = -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 (beta = -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 (beta = 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., beta = -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. Ann Epidemiol 2011;21:128-138.