Suffering from at least one of 70 common conditions may increase your risk of developing dementia, a study suggests.
Alzheimer's disease, the most common form of dementia affects seven million Americans and is on the rise nationwide.
It is generally considered a disease of old age, usually striking after age 65, but in recent years, scientists have discovered habits and conditions that start decades earlier can kickstart the disease by triggering harmful inflammation and damaging brain cells.
Now, researchers at Vanderbilt University and the University of Chicago have honed in on four groups of pre-existing conditions. Using electronic health records, the team tracked 150 million people over a 10-year window before just over 40,000 developed Alzheimer's disease.
They found that Alzheimer's diagnoses were more common among people with at least one of 70 different conditions.
The conditions fall under four categories: mental health disorders such as depression, neurological conditions like sleep disorders, circulatory disorders such as high blood pressure and endocrine or metabolic disorders such as diabetes.
Mental health conditions are thought to cause inflammation and shrink the hippocampus, the brain's memory center, while sleep disorders have been shown to disrupt the brain's waste clearance system.
Scientists believe circulatory disorders reduce blood flow to the brain and cause harmful oxygen shortages, while metabolic conditions lead to inflammation and insulin resistance, reducing the brain's ability to clear out toxic plaques linked to Alzheimer's disease.
The researchers behind the new study believe detecting these conditions earlier in life could help prevent or slow Alzheimer's disease in old age.
Xue Zhong, corresponding study author and professor in the Division of Genetic Medicine and Clinical Pharmacology at Vanderbilt University Medical Center, said: 'If we know the full inventory of medical conditions that predict Alzheimer's disease development 10 or more years later, we can potentially intervene before clinical symptoms of memory and/or cognitive impairment become apparent.'
'It is projected that delaying the onset of Alzheimer's disease by just five years could cut the incidence rate in half.'
About one in five US adults, or 60 million, have some form of mental health disorder, while 180 million have a neurological disorder. About 127 million have some form of circulatory conditions and 93 million have a metabolic syndrome.
The study, published in the journal Alzheimer's Research & Therapy, looked at electronic health records from two independent databases. The ream used MarketScan, a US claim-based database with over 150 million people, and Vanderbilt Health's electronic health record system, which has three million patients.
Of the roughly 150 million patients, the researchers found 43,508 with an Alzheimer's disease diagnosis, and 419,455 age- and sex-matched healthy controls in the MarketScan database. In Vanderbilt's system, they found 1,320 Alzheimer's cases and 12,720 healthy controls.
About 90 percent of Alzheimer's cases identified occurred after age 65. About 56 percent were women who had at least 10 years of health records prior to their diagnosis.
The MarketScan dataset showed 406 conditions that occurred more often in people who developed Alzheimer's later in life, while the Vanderbilt data showed 102.
Across both sets of data, there were 73 conditions seen more often in Alzheimer's patients. Mental health conditions included depression, anxiety, psychosis, hallucinations, suicidal ideation and speech and cognitive issues, among others.
The neurological category included sleep disorders such as insomnia and sleep apnea, movement issues like tremors and other neurological degeneration. Conditions in the cardiovascular group included high blood pressure and high cholesterol, and the metabolic group included type 2 diabetes, among others.
The researchers also identified vitamin deficiencies, thyroid disorders, urinary incontinence and musculoskeletal conditions such as arthritis and carpal tunnel syndrome.
Researchers noted that associations based on electronic health records (EHRs) do not show definitive proof that these conditions cause Alzheimer's disease, but they may help detect dementia earlier.
'Longitudinal EHRs offer a powerful view into the decades-long development of Alzheimer's disease,' Zhong said. 'By identifying medical patterns that consistently precede Alzheimer's disease, we can unlock new opportunities for risk reduction, early intervention and improved patient outcomes.'