Background:
Education is a critical determinant of health, and thus access to quality education through tertiary levels is included in Sustainable Development Goal (SDG) 4. This study aims to estimate the reduction in all-cause adult mortality risk that is associated with increased education globally and in distinct regions.

Methods:
We conducted a systematic review and meta-analysis of all studies capturing the effects of education on adult mortality. Mixed-effects Bayesian meta-regression models were implemented to address heterogeneity in referent and exposure measures and to adjust for study-level confounders including age, sex, wealth, marital-status, and race/ethnicity.

Results:
The review produced 9,750 effect measures extracted from 557 studies spanning 56 countries. The data biased towards High-income countries (HIC) at 86% of the sample, with 0.54% of results from Sub-Saharan Africa and none from North Africa and the Middle East. There was a dose-response relationship between education and adult mortality resulting in an average reduction in mortality risk of 1.42% (95%CI 1.24-1.59) per additional year. Compared to 0 years of education, achieving 6 years of education reduced mortality risk by 3.15%(1.5-4.89), improving to 8.83% (6.11-11.65) at 12 years and 25.56% (22.36-28.7) after 18 years. There were distinctly different effects of education on mortality risk in HICs compared to others, with an additional average yearly protective effect of 0.88% (0.16-1.44) among non-HICs.

Conclusion:
We identified an unequal distribution of studies estimating the impacts of education on mortality, particularly in Africa and the Middle East. We quantified the global impact of education on adult mortality and showed that lower education is a risk factor for premature mortality across regions even after controlling for other markers of socioeconomic status. This study provides robust evidence that SDG goals to keep learners in school through secondary and tertiary levels are a mechanism to improve long-term population health.