The Health Professionals Follow-Up Study (HPFS) is a long-term research project that began in 1986. It involves a cohort of over 50,000 male health professionals, including doctors and dentists, who provide detailed information about their health, lifestyle, and diet through regular questionnaires. The study aims to identify risk factors for chronic diseases such as heart disease, cancer, and diabetes. The HPFS is part of a larger initiative that includes the Nurses' Health Study, which focuses on female health professionals. Together, these studies contribute valuable data to understand how various factors influence health outcomes over time, helping to inform public health guidelines and medical practices.