Other studies of lowincidence
populations in Southeast/East Asia have generally found
nulliparity and late age at first birth to be related to increased breast
cancer risk although an inverse relation with breastfeeding
has been seen less often, possibly because high levels of prolonged
breastfeeding continue to be the norm. Two other studies of
breast cancer in Thai women also found no case-control differences
in parity, although their results may also have been affected by
methodological problems. We did not have information on age at
menarche or age at menopause so were unable to assess the effects
of these factors in this cohort.