The connection with breastfeeding was much less strong in women who already had a history of dementia in their family, indicating that genetic risks may outweigh the benefits from nursing.
The Cambridge study included a relatively small group of women - 81 - when they were between 70 and 100 years old. Some of the women had Alzheimer's, some did not.
Interviewing the women and their families, the researchers collected information about children, breastfeeding and other risk factors that might account for their dementia.
Previous research suggests women who breastfeed have a reduced risk of breast and ovarian cancers later in life, and perhaps a lower risk of heart disease, high blood pressure and diabetes, particularly in women who experience gestational diabetes.
And studies have already shown there may be a link between breastfeeding and a woman's general cognitive decline later in life. But the Cambridge study suggests some new ways of understanding what makes someone susceptible to Alzheimer's relative to their reproductive history, Fox said.
Another British study, published on August 6 in the Journal of Advanced Nursing, found that women whose personalities are more extroverted and less anxious may be more likely to breastfeed than women who are introverted and more anxious.
The study by scientists at Swansea University involved 602 mothers with infants six to 12 months old. Women who indicated that they were extroverts and were emotionally stable were significantly more likely to initiate and continue breastfeeding longer. Mothers who were introverted or anxious were more likely to only use formula or breastfeed for only a short time.
The researchers suggest that introverted women may be more self-conscious about breastfeeding in front of others and those who were more anxious felt they could not get the support they needed.
Researchers are keenly interested in obstacles to breastfeeding, mainly due to the benefits for babies. Besides links to higher IQ and physical development, breast milk has antibodies that can help babies fend off infections of the ear, lung and gut and reduce risks for allergies and asthma, sudden infant death syndrome and perhaps other illnesses later in life.
The latest possible benefit: a study at the University of Illinois at Champaign found that of 47 children who began stuttering at an early age, those who were breastfed as infants were as much as six times more likely to stop stuttering over time and return to fluent speech.
The August report in the Journal of Communication Disorders, notes that earlier research has shown ties between language development and breastfeeding, possibly because of fatty acids found in breast milk, but not formula, that boost brain function related to speech and language skills.
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