January 30, 2014
News Review From Harvard Medical School -- Estrogen, Diabetes Linked with Dementia Risk
Women who have high levels of estrogen even after menopause may be more likely to develop dementia, a study finds. The risk is especially high for those who also have diabetes. In this study, their risk of diabetes was 14 times as high as for women who had lower estrogen and no diabetes. The study included 675 women who had passed menopause and did not take hormone replacement therapy. All were age 65 or older when the study began. Researchers kept track of the women for about 4 years. In that time, women were twice as likely to develop dementia if they had high estrogen levels. All of these comparisons accounted for other health factors that also can increase the risk of dementia. Women with diabetes had such a high risk in part because their estrogen levels were so high. Those with dementia had 70% higher estrogen levels than diabetic women without dementia. The journal Neurology published the study online. HealthDay News wrote about it January 29.
By Robert H. Shmerling, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Not so long ago, it was common for doctors to prescribe estrogen-containing "hormone replacement therapy" for women after menopause. In fact, one of my mentors told me, "All postmenopausal women should be taking estrogen unless they can't or won't."
Evidence linked this treatment with several benefits. It lowered the risk of osteoporosis. It was also thought to lower the risk of heart attack and dementia. Some experts believed that during menopause, falling estrogen levels might increase dementia risk. So it made sense that estrogen treatment might prevent dementia.
But then better studies were done. They showed that estrogen use was actually linked to a higher risk of heart attack and stroke. Estrogen-replacement therapy quickly fell out of favor.
Still, the effect of estrogen on brain health has remained uncertain.
A new study looks at the relationship between blood estrogen levels and the risk of developing dementia. The study included 675 women. All of them were at least 65 years old. Here's what happened during the next 4 years:
- About 20% developed dementia.
- Researchers accounted for other factors known to increase dementia risk. After this adjustment, women with the highest estrogen levels were twice as likely to develop dementia as those with lower levels.
- Women with high estrogen levels and diabetes had 14 times the dementia risk as women with neither.
- Among women with diabetes, those with dementia had estrogen levels that were 70% higher than those without dementia.
These results surprised me. After all, most women with dementia are past the age of menopause. That's a time of life when estrogen levels fall. So why would higher estrogen levels in these women increase the risk of dementia? This study was not designed to answer the question. But it's possible that both diabetes and estrogen affect the brain's blood vessels and the tendency of blood to clot. Those effects could lead to brain injury, including stroke.
People who are obese tend to have higher estrogen levels. Obesity also increases the risk of diabetes. And diabetes is linked with a higher risk of dementia. So it's possible that the real culprits are obesity and diabetes, not high estrogen levels. To address this, the researchers accounted for body mass index and waist-to-hip ratio in their analysis. However, these are not perfect measures of a person's body fat.
So this is unlikely to be the last word on how estrogen levels and diabetes affect dementia risk.
What Changes Can I Make Now?
You can make changes now to reduce your risk of diabetes and dementia. This is particularly important if you have a family history of diabetes or other conditions that increase your risk of dementia or heart and artery disease. These conditions include high blood pressure and high cholesterol.
Here's what you can do to reduce your risk of diabetes:
- Exercise regularly.
- Maintain a healthy weight.
- Choose a diet that's high in fiber, fruits and vegetables and low in saturated and trans fats.
- Don't smoke.
- Get your blood pressure and cholesterol levels checked regularly. If they are high, work with your doctor to keep them in a healthy range.
- Consider taking a medicine (called metformin) if you have "pre-diabetes" (slightly high blood sugar) or other factors that increase your diabetes risk. These factors include:
- Family history of diabetes
- Excess weight or body fat around the waist
- Having diabetes during pregnancy
Many of these measures may also reduce your risk of dementia. You also can make other changes that might reduce dementia risk:
- Choose a diet that's high in omega-3 fatty acids.
- Keep your mind active with a busy social life, hobbies or a memory training program.
What about the possibility that high estrogen levels increase the risk of dementia? Avoiding obesity and estrogen supplements are currently the best ways to prevent higher blood estrogen levels.
What Can I Expect Looking to the Future?
You can expect fewer women to take estrogen treatment after menopause. However, hormone therapy still may be offered at times. For example, short-term, low-dose hormone therapy may be considered for women with major menopause symptoms (such as severe hot flashes) that have not improved with other treatments.
Our population is aging, and more cases of diabetes are being diagnosed each year. So it's likely that the number of people with dementia will continue to increase. The discovery that estrogen levels may affect the risk of dementia could lead to new preventive measures and treatments in the future.