Longer Reproductive Years Lower Dementia Risk in Women With Type 2 Diabetes

A research study has found that postmenopausal women with type 2 diabetes who have a longer reproductive lifespan experience a reduced risk of developing dementia.

The study, led by Professor Lee Seung-hwan of the Division of Endocrinology at the Catholic University of Korea’s Seoul St. Mary’s Hospital and Professor Han Kyung-do of the Department of Statistics and Actuarial Science at Soongsil University, analyzed the influence of reproductive factors on cognitive decline in women with diabetes.

The findings were published in a study involving 159,751 postmenopausal women with type 2 diabetes aged over 40 years. These participants underwent health examinations in 2009, and the research team utilized data from the National Health Information Database and self-administered questionnaires to track reproductive factors.

Study Findings on Reproductive Lifespan

Over a median follow-up period of 8.3 years, the researchers identified 24,218 cases of all-cause dementia. This total included 18,819 cases of Alzheimer disease and 2,743 cases of vascular dementia.

The study divided participants into four groups based on the duration from menarche to menopause: less than 30 years, 30 to 34 years, 35 to 39 years, and 40 years or more.

Women with a reproductive lifespan of 40 years or more showed a lower risk of all-cause dementia compared to those with a lifespan of less than 30 years, with a hazard ratio of 0.73 (95% CI 0.69-0.78). The researchers noted that comparable effects were observed for both Alzheimer disease and vascular dementia.

Impact of Parity and Hormone Therapy

Beyond the total duration of the reproductive span, the study examined other reproductive factors, including parity and the use of hormone replacement therapy (HRT).

• Women with parity 1 had a 27% lower risk of all-cause dementia compared with women with parity 0.
• Women who used HRT for more than 5 years had a 17% lower risk of all-cause dementia compared with those who did not use HRT.

The researchers suggested that these findings are linked to endogenous estrogen exposure, which has been associated with a reduced risk of cognitive decline.

Public Health Context and Diabetes Risk

The research addresses a significant public health concern, as dementia is one of the fastest-growing geriatric diseases worldwide. The World Health Organization estimates that more than 55 million people globally have dementia, a figure projected to reach 150 million by 2050.

In South Korea, the Ministry of Health and Welfare’s 2023 Dementia Epidemiology Survey indicated that the prevalence rate among adults aged 65 and older reached 9.25 percent. Women account for approximately 58.8 percent of all dementia patients, showing a higher incidence rate.

Diabetes is recognized as a major risk factor for the condition. According to a 2024 report by the Lancet Commission, diabetes increases the risk of dementia by approximately 1.7-fold.

Prior to this study, the specific ways in which reproductive factors—such as childbirth history, breastfeeding history, reproductive span, and hormone therapy—affect dementia risk specifically in women with type 2 diabetes had not been clearly established.