Which factor is associated with a decreased risk of breast cancer?

Breastfeeding is associated with a decreased risk of breast cancer for several reasons. Studies have shown that lactation alters the breast tissue, making it less susceptible to cancerous changes. During breastfeeding, the cells within the breast undergo differentiation, which enhances their maturation and potentially reduces the likelihood of malignant transformation.

Additionally, breastfeeding often leads to a reduction in the overall lifetime exposure to hormones such as estrogen. This decreased hormonal exposure is believed to be protective against the development of hormone-sensitive breast tumors. Furthermore, the duration of breastfeeding is inversely related to breast cancer risk; the longer a mother breastfeeds, the more protective the effect appears to be.

In contrast, factors such as having a first full-term pregnancy after the age of 35, experiencing early menarche, and being nulliparous are generally associated with an increased risk of developing breast cancer. Delayed childbirth can lead to longer exposure to endogenous estrogens, while early menarche increases the total duration of hormonal exposure, and nulliparity is linked to a lack of protective factors that come from childbirth and breastfeeding. Thus, breastfeeding stands out as a key lifestyle practice for reducing breast cancer risk.