Menopause refers to a stage in which a woman transitions from the reproductive period to the non-reproductive period, which is mainly manifested by the gradual decline of ovarian function, irregular menstrual cycles until they finally stop, accompanied by significant changes in the levels of estrogen and other sex hormones. Normally, menopause usually begins between the ages of 45 and 55, with an average age of about 51. Menopause that occurs within this range is considered "normal" or "age-appropriate".
Early menopause and risk of dementia (before age 45)
Hormonal changes: Estrogen has a neuroprotective effect and is involved in the growth and survival of neurons in the brain. Early menopause, which leads to an early decrease in estrogen levels, may deprive the brain of the protective effects of estrogen for a longer period of time, potentially increasing the risk of cognitive decline and dementia.
Oxidative stress: Estrogen also has antioxidant properties that protect against oxidative stress, which plays a role in the development of Alzheimer's disease. An early decline in estrogen levels may lead to increased susceptibility to oxidative damage.
Genetic and environmental factors: Early menopause can be influenced by a variety of factors such as genetics, medical treatments (such as chemotherapy or oophorectomy surgery), lifestyle (such as smoking), and these factors may also independently increase the risk of dementia.
Late onset menopause does not mean a reduced risk of dementia (after age 55)
Persistent hormone exposure: conversely, chronically high levels of estrogen due to late menopause may increase the risk of dementia by promoting the formation of amyloid plaques in β, but the results have been inconsistent.
Vascular health: Estrogen has an impact on vascular health, and long-term hormone exposure can have both protective and adverse effects on the cardiovascular system, which in turn can affect brain health and dementia risk.
Summary of the study
Several large-scale epidemiological studies have explored the link between the timing of menopause and the risk of dementia. While some studies have found that women who experience early onset menopause may be at higher risk of dementia later in life, the evidence for late onset menopause is mixed, with some studies showing a protective effect and others showing no effect or increased risk.
Factors that affect the early and late stages of menopause
Genetic factors: Women who have a family history of early or late menopause may also enter menopause earlier or later themselves.
Ovarian function: Conditions such as premature ovarian failure, ovarian damage, or inflammation can directly lead to early menopause.
Chronic diseases, such as diabetes, especially type 2 diabetes, can accelerate ovarian decline and lead to early menopause.
Reproductive and lactation history: older age at first pregnancy, fewer pregnancies, and longer breastfeeding may be associated with later menopause and vice versa.
Lifestyle and psychological stress: Long-term mental stress, high work intensity, fast pace of life, lack of exercise, unbalanced nutrition, smoking and drinking, excessive dieting, staying up late and other bad lifestyle habits may promote early menopause.