Recurrence pattern: Every year on the fourth Thursday of November.

National Family Health History Day is observed in the United States on every fourth Thursday of November, coinciding with Thanksgiving Day. Established in 2004 by U.S. Surgeon General Richard Carmona, the day emphasizes the importance of understanding one's family health history, which includes information about health disorders among direct blood relatives. Families are encouraged to gather during Thanksgiving to discuss their health histories, as this can help identify predispositions to various illnesses such as autoimmune disorders, cancers, cardiovascular diseases, diabetes, and mental disorders. Participants are advised to document their relatives' health conditions, ages at diagnosis, and other pertinent details, and to regularly update this information. The Office of the U.S. Surgeon General also provides resources like My Family Health Portrait, a website designed to assist families in recording and sharing their health histories. Ultimately, the observance serves as a reminder that knowing family health history is crucial for proactive healthcare and preventive measures.