Los Angeles, Nov 18 (PTI): Women have better brainpower after menopause if they had their last baby after age 35, according to a new study.

The study suggests that the same will be true for those who used hormonal contraceptives for more than 10 years or began their menstrual cycle before turning 13.

This is the first study to investigate the association between age at last pregnancy, which can be a marker of a later surge of pregnancy-related hormones, and cognitive function in later life, said Roksana Karim, assistant professor at University of Southern California in the US.

"Based on the findings, we would certainly not recommend that women wait until they are 35 to close their family, but the study provides strong evidence that there is a positive association between later age at last pregnancy and late-life cognition," said Karim.

Postmenopausal women who had their last pregnancy after 35 had better verbal memory. Those who had their first pregnancy when they were 24 or older had significantly better executive function, which includes attention control, working memory, reasoning and problem solving.

The main hormones at play are estrogen and progesterone. In animal studies, estrogen has a beneficial impact on brain chemistry, function and structure; progesterone is linked with growth and development of brain tissue, Karim said.

The study included 830 women who, on average, were 60 years old. The data was adjusted for age, race and ethnicity, income and education.

Participants were given a series of tests that included assessments of verbal memory - remembering a list of words or retelling a story after some distraction - psychomotor speed, attention and concentration, planning, visual perception and memory.

The study found that other reproductive events were also important to later life cognition. More time between first and last period - longer reproductive life - proved valuable for executive function.

"Starting your period early means you have higher levels of the female sex hormone being produced by the ovaries," Karim said.

"Girls are receiving the optimal levels early, so it is possible that their brain structures are better developed compared to those who are exposed to estrogen levels associated with menstrual cycles at a later age," she said.

Use of the pill or other hormonal contraceptives for at least 10 years was beneficial for verbal memory and critical thinking ability.

"Oral contraceptives maintain and sustain a stable level of sex hormones in our blood stream," Karim said.

Women who did not carry their pregnancy to term and those who gave birth to two children had better overall cognitive ability, verbal memory and executive function when compared to women who had only one full-term pregnancy. The study appears in the Journal of the American Geriatrics Society.