Global Research Team
David E. Bell Postdoctoral Research Fellow
Harvard University, Epidemiology
Hayami Koga is a David E. Bell Postdoctoral Research Fellow at the Harvard Center for Population and Development Studies (Harvard T.H. Chan School of Public Health). She holds a Ph.D. in population health sciences from Harvard's Department of Social and Behavioral Sciences and an M.D. from the University of Occupational and Environmental Health in Japan. Her research examines associations between psychological wellbeing — including optimism and emotional wellbeing — healthy aging, and workplace wellbeing, with a focus on cross-national patterns.
The distribution of optimism across sociodemographic groups in 22 countries
Scientific Reports · 2025
The Global Flourishing Study: Study Profile and Initial Results on Flourishing
Nature Mental Health · 2025
When the glass is half full: early life experiences and adult optimism in 22 countries
npj Mental Health Research · 2025