The main cause of dementia is a brain disorder called Alzheimer’s disease, but other reasons can affect memory and reasoning. Some causes, such as poor sleep, head injuries, and physical inactivity, can lead to memory loss later in life. Genetics and aging are major risk factors for memory loss and dementia. About a third of people aged 85 years or older may experience dementia, so it is important to understand the early signs and risk factors associated with the condition.
POOR SLEEP
Poor sleep affects the brain in many ways. Over time, it may lead to brain inflammation and other processes that contribute to Alzheimer’s disease. Other sleep issues, including insomnia, sleep apnea, sleeping less than five hours or more than 10 hours a night, and poor sleep quality in general, can also increase the risk of dementia. Alzheimer’s disease can lead to even worse sleep. This can negatively affect the symptoms of the condition.
LONELINESS
Social isolation may contribute to the decline of certain cognitive functions, including memory. Socializing may help protect against dementia.3
Engaging in activities with other people and having larger social networks later in life is associated with better cognitive functioning. It is also possible that isolation is not a cause of dementia, but an early symptom. People who experience memory loss may no longer be able to participate in their hobbies or keep up with their favorite sports team, leading to withdrawal from social interaction.
HEAD INJURIES
Head injuries, also called traumatic brain injuries (TBIs), can increase your risk of dementia. A mild TBI is also known as a concussion. The risk of dementia is higher in people who have experienced multiple TBIs or a severe TBI.6 Why this occurs is unclear and possibly depends on the severity of the injury.
AIR POLLUTION
Exposure to air pollutants has been linked to an increased risk of dementia. Specifically, high levels of PM2.5 and NO2/NOx in the air can lead to inflammation in the brain. PM2.5 stands for tiny particulate matter (particle pollution) that can come from sources such as power plants, construction sites, and fires.9 NO2/NOx are harmful gases emitted from burning fuel in cars and power plants. Breathing air with a lot of NO2 can lead to respiratory issues such as asthma, per the EPA. PM2.5 air pollution has been linked to a variety of health issues in addition to dementia, such as heart disease, kidney disease, hypertension (high blood pressure), and type 2 diabetes.
HEAVY ALCOHOL USE AND SMOKING
Heavy alcohol use can cause changes in brain structures, possibly leading to cognitive issues. Specifically, drinking more than 21 units of alcohol (about two bottles of wine) weekly can lead to an increased risk. It is unclear whether light or moderate drinking can hurt your cognitive functioning later in life. One study found that light to moderate alcohol use led to atrophy (shrinking) of the hippocampus after 30 years. The hippocampus is part of the brain that helps store memories. Others have found that light to moderate drinking has protective benefits. Try to limit your drinking to about 14 units per week—about 6 pints of average-strength beer—spread out over multiple days. Smoking is also associated with dementia. Avoiding smoking may reduce this risk.
HEARING LOSS
Hearing loss is associated with a higher risk of Alzheimer’s disease. The exact reason for this connection is unknown, but there are several theories. One is that hearing loss can lead to increased social isolation—another risk factor for dementia. The other is that losing hearing makes the brain work harder to make up for the impairment, leading to fewer resources for other cognitive functions. It is also possible that hearing loss and dementia develop through similar brain mechanisms.
HEART DISEASE
Brain and heart health are closely connected. The brain uses 20% of the body’s oxygen and energy supplies. Heart disease and its risk factors—such as smoking and diabetes—are also associated with dementia. Physical activity and a heart-healthy diet—with fruits, vegetables, whole grains, fish, nuts, and legumes—can protect against heart disease, which can, in turn, reduce the risk of cognitive decline. There is no one particular diet that can directly lower your risk of dementia.
HIGH BLOOD PRESSURE
Blood pressure readings come with two numbers: systolic and diastolic blood pressure. Systolic pressure is measured when your heart beats, and diastolic pressure is measured between beats. Healthy systolic blood pressure is below 120 millimeters of mercury. Your risk of dementia increases when this number is 130 millimeters of mercury or higher in midlife (at 50 years old). Getting treatment for high blood pressure and keeping it in check in your midlife can help.3 High blood pressure that develops later in life may actually have a protective effect.
PHYSICAL INACTIVITY
Being physically active can reduce your risk of dementia. Researchers do not know how much or what type of exercise is best. Aerobic exercise, or cardio, had a small but beneficial effect in some studies.
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