Which factor is associated with an increased incidence of breast cancer?

Nulliparity, or the state of never having given birth, is indeed associated with an increased risk of breast cancer. This is because pregnancy and breastfeeding can have protective effects against the development of breast cancer. During pregnancy, breast cells undergo changes that can lead to a more differentiated state, which may reduce their susceptibility to mutations that cause cancer. Additionally, the hormonal changes associated with pregnancy and lactation can also lower the overall exposure to estrogen over a woman’s lifetime, which is a risk factor for breast cancer.

In contrast, late menarche, trauma to the breast, and early natural menopause have not shown a strong or direct correlation with increased breast cancer risk. Late menarche is typically associated with a lower risk, as it may reflect a shorter lifetime exposure to oestrogens. Trauma to the breast is not considered a significant factor in breast cancer development. Early menopause, which reduces the number of menstrual cycles a woman experiences, often correlates with lower levels of estrogen exposure, which can also reduce breast cancer risk. Therefore, nulliparity stands out as a significant risk factor for breast cancer development.