The worldwide prevalence of dementia - conditions related to decline in memory, language, problem-solving and other thinking skills - has increased 30% since 2010. With dementia on the rise, more information about its symptoms and causes is needed. Recent research is revealing specific risk factors for memory loss.

1. High Blood Pressure During Mid-Life 

Researchers at Johns Hopkins University Medical School found that individuals with high blood pressure during middle age and later life were 49% more likely to develop dementia than those with normal blood pressure during both life stages, while those with high blood pressure at mid-life and low blood pressure in later life had a 62% increased risk of dementia.

Published in August, the study was based on data from more than 4,700 participants. High blood pressure was defined as 140/90 millimeters of mercury or higher, while low blood pressure was defined as 90/60 or lower.

High blood pressure can stem from genes or lifestyle factors such as not getting enough exercise and poor dietary habits. More than 75 million Americans, or about one in three adults, have high blood pressure. 

2. Mid-Life Stress Puts Women, But Not Men, At Risk 

Affecting 5.8 million Americans, Alzheimer’s disease is the most common form of dementia worldwide and the sixth leading cause of death in the United States. There are currently no treatments for preventing or slowing the progression of Alzheimer’s, and it’s not clear why women represent two-thirds of those impacted by the disease.

A study of 900 Baltimore adults by researchers at Johns Hopkins University School of Medicine may shed some light. The researchers found that stressful midlife events such as marriage, divorce, death of a loved one, job loss, severe injury or sickness, a child moving out, retirement or birth of a child increase dementia risk only for women.

While the study does not demonstrate cause and effect, it does add to the evidence that stress hormones play an “uneven gender role” in brain health, according to a university statement. Researchers said that stress reduction has received less attention than other risk factors for Alzheimer’s, and they hope that the study will encourage greater emphasis on stress management techniques as a way to prevent or delay the onset of the disease.

3. Abnormally High and Low Iron Levels

Dutch researchers tracked 12,305 individuals with an average age of 65 over a 12-year period and found that individuals with abnormally low hemoglobin levels, a condition known as anemia, had a 34% greater risk of dementia from any cause and a 41% increased risk of Alzheimer’s dementia compared to people without anemia.

They also found an association between abnormally high hemoglobin levels and dementia risk. Hemoglobin is the iron-rich protein in red blood cells that carries oxygen from the lungs to the rest of the body. The analysis of brain MRI data accounted for age, gender, smoking, body mass index, cholesterol levels and other factors that could have impacted outcomes. By following thousands of people over a long period, the study confirms earlier research linking abnormal iron levels and dementia risk.

"Clinically, the current finding underscores the importance of not using iron supplements for treating anemia in older patients where there is no clear evidence of iron deficiency. There is growing concern that higher brain iron levels are associated with more aggressive disease in both AD and Parkinson's disease," Ashley Bush, director of the Melbourne Dementia Research Centre and professor of psychiatry and neuroscience at the University of Melbourne, Australia, told Medscape Medical News.

4. Common Prescription Medications

A study of nearly 285,000 individuals age 55 to 100, done by British researchers, found that a class of common prescription drugs called anticholinergics increased dementia risk by 50% when “strong” anticholinergics were taken daily for three years. The association was strongest in those diagnosed with dementia before the age of 80, which according to the authors indicated that such drugs should be prescribed “with caution” in middle age and older adults. Previous studies have also linked some anticholinergics to increased dementia risk.

Anticholinergics block the action of the neurotransmitter acetylcholine which is involved in heart rate, muscle movement, blood vessel dilation and other nervous system functions. They're used to treat a range of conditions from allergies and asthma to depression, epilepsy, and gastrointestinal issues and include the antihistamine Benadryl, the bladder drug Enablex and the antidepressant Paxil, among many others

According to the New York Times, older adults are likely to be taking many anticholinergics simply because they tend to have more medical problems, and they may be more sensitive to them because acetylcholine production decreases with age. Antidepressants, bladder drugs, antipsychotics and epilepsy medications were most problematic while no increased risk of dementia was found with antihistamines, muscle relaxants, bronchodilators, and stomach spasm and heart arrhythmia medications.

5. Liver Dysfunction 

A groundbreaking study by researchers at Duke University and the Alzheimer's Disease Neuroimaging Initiative has found new links between liver dysfunction, specifically altered liver enzymes, and Alzheimer’s disease. This study adds to the growing body of research tying Alzheimer’s disease to metabolic dysfunction such as diabetes and high cholesterol.

Metabolism is the process of getting energy from food. “Metabolic syndrome” is a cluster of conditions including high blood sugar, abnormal cholesterol and high blood pressure that increase the risk of heart disease, stroke and type 2 diabetes. 

"While we have focused for too long on studying the brain in isolation, we now have to study the brain as an organ that is communicating with and connected to other organs that support its function, and that can contribute to its dysfunction," Rima Kaddurah-Daouk, study co-author and professor of psychiatry and behavioral sciences at Duke University, told MedPage Today.