Chronotype and Breast Cancer Risk in a Cohort of US Nurses

Participants who self-reported as neither morning nor evening type had a 27% increased risk of breast cancer compared to definite morning types.

• Among 72,517 women, 1,834 breast cancer cases were confirmed from 1989 to 2007.
• Chronotype was categorized as definite morning type, probable morning type, probable evening type, definite evening type, or neither.
• No significant associations were found between other chronotypes and breast cancer risk.
• The increased risk for neither morning nor evening types suggests a possible link to circadian disruption.
• Further studies are needed to validate these findings.

AI simplified