The Nurses' Health Studies: a half-century of discovery in women's health

For five decades, the Nurses' Health Studies have been at the forefront of understanding how oral contraceptives, hormone therapy, other medications, diet, lifestyle, and other factors influence risk and survival for chronic disease. These landmark cohorts have driven major innovations in epidemiology—from methodological advances, including improved dietary assessment, validation studies, biorepository development, and ‘omics projects, to analytical and statistical breakthroughs encompassing mediation, correction for measurement error and missing data, assessment of aetiological disease heterogeneity, risk prediction, and multistate modelling. These studies have illuminated how dietary factors, obesity, physical activity, biomarkers, hormonal exposures, and reproductive factors might influence the prevention of chronic diseases, including cancer, diabetes, and cardiovascular diseases, and the promotion of healthy ageing. The Nurses' Health Study and the Nurses' Health Study II have shaped clinical and public health guidelines worldwide—from dietary recommendations and the US Food and Drug Administration trans fat ban to the International Agency for Research on Cancer carcinogen classifications and global strategies for chronic disease prevention. This enduring legacy reflects both committed investigators and the extraordinary dedication of participants over the past half-century.