Early menopause may raise risk of dementia later in life

"Our study found that women who enter menopause very early were at greater risk of developing dementia later in life," said Wenting Hao, M.D., a Ph.D. candidate at Shandong University in Jinan, China. "Being aware of this increased risk can help women practice strategies to prevent dementia and to work with their physicians to closely monitor their cognitive status as they age."

Dementia involves serious changes in the brain that impair a person's ability to remember, make decisions and use language. Alzheimer's disease is the most common type of dementia, while the second most common is vascular dementia, which is the result of disruptions in blood flow to brain cells caused by strokes or plaque build-up in arteries supplying blood to the brain. Both of these types of dementia are more common with age. Diseases affecting specific parts of the brain can also lead to dementia, and a person can have dementia due to more than one disease process.

In the current study, the researchers analyzed the potential relationship between age at menopause onset and the diagnosis of dementia from any cause. Health data was examined for 153,291 women who were an average age of 60 years when they became participants in the UK Biobank (between 2006 and 2010) were examined. The UK Biobank is a large biomedical database that includes genetic and health information on a half million people living in the United Kingdom.

The investigators identified the diagnosis of all types of dementia including Alzheimer's disease, vascular dementia and dementias from other causes. They calculated risk of occurrence in terms of the age at which the women reported having entered menopause, compared with the women who began menopause at average age of menopause onset, which is 50-51 years (51 years is the average age for menopause onset among women in the U.S.). The results were adjusted for factors including age at last exam, race, educational level, cigarette and alcohol use, body mass index, cardiovascular disease, diabetes, income and leisure and physical activities.

The analysis found:

• Women who entered menopause before the age of 40 were 35% more likely to have been diagnosed with dementia.
• Women who entered menopause before the age of 45 were 1.3 times more likely to have been diagnosed with dementia before they were 65 years old (called presenile or early-onset dementia).
• Women who entered menopause at age 52 or older had similar rates of dementia to those women who entered menopause at average age of menopause onset, which is the age of 50-51 years.

Although post-menopausal women are at greater risk of stroke than pre-menopausal women, and stroke can disrupt blood flow to the brain and may result in vascular dementia, in this study the researchers did not find an association between age at menopause and the risk of vascular dementia.

"Dementia can be prevented, and there are a number of ways women who experience early menopause may be able to reduce their risk of dementia. This includes routine exercise, participation in leisure and educational activities, not smoking and not drinking alcohol, maintaining a healthy weight, getting enough vitamin D and, if recommended by their physician, possibly taking calcium supplements," Hao said.

The researchers suggest that lowered estrogen levels may be a factor in the possible connection between early menopause and dementia.

"We know that the lack of estrogen over the long term enhances oxidative stress, which may increase brain aging and lead to cognitive impairment," Hao said.

Health care clinicians who care for women should be aware of a woman's age at menopause onset and closely monitor for cognitive decline in those who reached menopause before age 45.

"Further research is needed to assess the added value of including the timing of menopause as a predictor in existing dementia models," Hao said. "This may provide clinicians with a more accurate way to assess a woman's risk for dementia."

The study has several limitations. Researchers relied on women's self-reported information about their age at menopause onset. In addition, the researchers did not analyze dementia rates in women who had a naturally occurring early menopause separate from the women with menopause induced by surgery to remove the ovaries, which may affect the results. The data used for this study included mostly white women living in the U.K. and may not generalize to other populations.