- There is no effective treatment for Alzheimer’s disease, but scientists hope to identify early risk factors that doctors can target to prevent or slow its progress.
- An observational study has now highlighted 10 medical conditions associated with a diagnosis of Alzheimer’s disease up to 10 years later.
- The conditions include known risk factors for the disease, such as depression and hearing loss, and conditions with no links to the disease, such as constipation.
- The study does not reveal whether these conditions help cause Alzheimer’s or are early symptoms.
People with dementia experience a progressive loss of their ability to remember, think, and communicate effectively.
However, the changes in the brain that are responsible for dementia may begin decades before its effects on cognition and behavior become apparent.
The World Health Organization (WHO) indicates that of the 55 million people worldwide living with dementia, 60–70% have Alzheimer’s disease.
Attempts to develop an effective treatment for Alzheimer’s have met with little success. Researchers are increasingly turning their attention to detecting the disease early.
The key to this strategy is to identify early, “modifiable” risk factors that doctors can target with drugs or other interventions.
Researchers at the Paris Brain Institute in France have now found statistical associations between 10 health conditions and a diagnosis of Alzheimer’s disease up to 10 years later.
Major depression was the earliest condition to be associated with a subsequent diagnosis of Alzheimer’s, appearing at least 9 years in advance.
Other conditions that the study linked to a later diagnosis of Alzheimer’s included:
- anxiety
- constipation
- abnormal weight loss
- a type of arthritis called cervical spondylosis
- reaction to severe stress
- hearing loss
- sleep disorders
They also showed that falls and fatigue had links to Alzheimer’s risk.
The next step will be to determine whether these conditions help cause the disease or whether they are early signs of changes in the brain that are already happening.
“Diseases like Alzheimer’s can begin in the brain up to 2 decades before symptoms start to show,” said Katy Bray, Ph.D., told Medical News Today. Dr. Bray is a public engagement manager at Alzheimer’s Research UK and was not involved in the research.
“It is difficult to know how these conditions may contribute to the development of the disease or if they could also be very early symptoms,” Dr. Bray told Medical News Today.
The study appears in The Lancet Digital Health.
How the study worked
The researchers analyzed the primary healthcare records of 20,214 people with Alzheimer’s disease in the United Kingdom and 19,458 people with Alzheimer’s in France.
They compared each person’s medical records with a control matched for sex and age who had not received a diagnosis of a progressive brain disease during the 15-year study period.
Out of the 123 health conditions they investigated, 10 had a statistically significant association with a diagnosis of Alzheimer’s disease 2–10 years later in France and the U.K.
Some of the conditions, such as depression, hearing loss, and sleep disorders, are already known risk factors for Alzheimer’s.
However, this study was the first to identify constipation as a possible risk factor. The link between the two conditions became apparent 7 years before the diagnosis of Alzheimer’s.
Interestingly, constipation is also associated with depression and is an established early sign of other brain diseases, such as Lewy-body dementia and Parkinson’s disease.
“The connections made allowed us to confirm known associations, such as hearing problems or depression, and other less-known factors or early symptoms, such as cervical spondylosis or constipation,” says Thomas Nedelec, Ph.D., the first author of the study.
“The question remains as to whether the health problems encountered are risk factors, symptoms, or warning signs of the disease,” he added.
In their paper, the authors conclude:
“Our findings make it possible to model the possible trajectories of risk factors in the period preceding the diagnosis of Alzheimer’s disease, providing new insights into possible windows for prevention.”
The study had some notable limitations. For example, it was unable to take other risk factors that contribute to Alzheimer’s, including education level, ethnicity, socioeconomic status, and genetics, into account.
Importance of mental health care
“This study adds a wealth of data to our understanding of mental disorders, such as depression, as a risk factor for dementia,” said Claire Sexton, Ph.D., director of scientific programs and outreach at the Alzheimer’s Association in the United States, who was not involved in the study.
However, she emphasized that because their study was observational, rather than a clinical trial, for example, the scientists were unable to establish whether depression helps cause Alzheimer’s.
“Just because someone has depression does not mean they will go on to develop Alzheimer’s,” Dr. Sexton told MNT.
“However, these data support the idea that taking care of one’s mental health is incredibly important for overall well-being and potentially cognitive health,” she added.
Another recent study also found an association between mental health conditions and dementia.
Strong potential for prevention
In 2020, the Lancet Commission on dementia added three new modifiable risk factors: excessive alcohol consumption, head injury, and air pollution to its existing list, which includes:
- hypertension
- smoking
- obesity
- depression
- physical inactivity
- diabetes
The report concluded that modifying all the risk factors that researchers have identified could prevent or delay dementia in up to 40% of people.
“While midlife is emerging as a key time for dementia risk, it’s never too early or too late in life to take action on brain health,” Dr. Bray told MNT.
“This includes not smoking, only drinking in moderation, staying mentally and physically active, eating a balanced diet, and keeping cholesterol and blood pressure levels in check,” she said.
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