Women with depression between the ages of 40 and 60 are twice as likely to develop young-onset dementia, largely driven by declining estrogen levels and female sex hormones as they experience menopause, a recent study showed Tuesday.

Young-onset dementia is when a person develops any form of dementia before the age of 65.

The likelihood of developing dementia at an early stage was 2.5 to 2.7 times higher for women in their middle adulthood diagnosed with depression when compared to their peers without depression, according to research by a group of medical professors at Seoul National University Healthcare System Gangnam Center. The three professors are Yoo Jung-eun, a family medicine professor; Yoon Dae-hyun, a psychiatry professor; and Jin Eun-hyo, a professor at the Department of Gastroenterology.

The data came to light after the team observed 1.6 million women aged between 40 and 60 through health checkups under the country's National Health Insurance Service for nine years from 2009. This included 946,931 premenopausal and 674,420 postmenopausal women.

In particular, the risk of developing dementia was higher in women with depression who experienced early menopause or delayed menstruation, due to physiological changes in women related to shifts in the body's hormone levels.

"During the menopausal transition, women experience dramatic hormonal changes, which may impact both mood and cognitive decline," the study pointed out.

"This is attributed to estrogen, a female sex hormone that may play a protective role against neural degeneration. With aging, estrogen levels decline, leading to increased exposure to mitochondrial toxicity and beta-amyloid accumulation, increasing the risk of dementia," it explained.

Professor Yoo underscored the importance of going through screenings at hospitals that could detect and diagnose certain illnesses and taking care of mental health to reduce the risks of developing dementia among middle-aged women.

"Women with depression, especially those having a shorter period of exposure to female hormones like estrogen due to early menopause, need to make efforts to prevent dementia from coming early," the professor noted.

This study was recently published in the medical journal Alzheimer’s Research and Therapy.