San Francisco, Jun 20 (IANS): Women who have their ovaries removed before menopause, particularly before the age of 40, have reduced white matter integrity in multiple regions of the brain later in life, a new study said on Thursday.

White matter refers to the nerve fibres that connect neurons in different areas of the brain.

In the study published in the journal Alzheimer's & Dementia, the researchers analysed data from the Mayo Clinic Study of Aging to identify women over the age of 50 with available diffusion tensor imaging, a magnetic resonance imaging (MRI) technique that measures white matter in the brain.

"We know that having both ovaries removed before natural menopause causes abrupt endocrine dysfunction, which increases the risk of cognitive impairment and dementia," said Michelle Mielke, PhD, professor at the US-based Wake Forest University School of Medicine.

Researchers found that females who had premenopausal bilateral oophorectomy (PBO) before the age of 40 had significantly reduced white matter integrity in multiple regions of the brain.

"There were also trends in some brain regions such that women who had PBO between the ages of 40-44 or 45-49 years also had reduced white matter integrity, but many of these results were not statistically significant," said Mielke.

She also said that 80 per cent of participants who had their ovaries removed also had a history of estrogen replacement therapy.

Therefore, the study was not able to determine whether the use of estrogen replacement therapy after PBO mitigated the effects of PBO on white matter integrity.

"Having both ovaries removed results in an abrupt decrease in both estrogen and testosterone in women. Therefore, one possible explanation for our results is the loss of both estrogen and testosterone," Mielke mentioned.