Problems with cognition and memory are not necessarily a normal aspect of aging, and they should not be ignored, an MGH neuropsychologist cautions. The first step in addressing these problems is to get a thorough medical assessment to rule out cardiovascular disease, hypothyroidism, and many of the other medical issues that may be associated with cognitive changes in older age.
A wide variety of physical disorders can cause cognitive symptoms. For example, insulin resistance—a decreased ability of insulin to lower blood sugar levels that often precedes the development of diabetes—is associated with atrophy of regions of the brain affected by early Alzheimer’s disease (AD), according to a study published in the February 2013 issue of Diabetes Care. And obstructive sleep apnea (OSA), a disorder in which repeated closures of the airways during sleep interrupt the delivery of oxygen to the brain, significantly increases risk for dementia among older adults, according to a study published in the February 12, 2013 issue of Neurology.
“The brain requires a healthy body to function at its best,” says Dara Manoach, PhD, a neuropsychologist and researcher at MGH who specializes in sleep and memory. “Studies like these demonstrate that medical conditions that affect the body’s organ systems, or combinations of organ systems, can have serious effects on cognition. Anything that changes brain metabolism, disrupts sleep, or affects blood flow, respiration, and blood oxygen levels impacts the brain, and especially the hippocampus, a highly metabolically active and vulnerable brain region that is most involved in memory.
“Regular medical assessments can help increase your chances of staying sharp as you age by facilitating the prevention, diagnosis, and management of disorders that are known to negatively affect the brain.”
Almost any physical problem has the potential to alter brain function, either as a result of physiological changes linked to the ailment, or from related factors, such as pain and fatigue. Common medical issues associated with impaired cognition include:
- Diabetes and insulin resistance can lead to atrophy of brain memory regions; diabetes has also been linked to higher risk for disease of the small blood vessels and impaired circulation in the brain.
- Cushing’s disease, a disorder affecting the pituitary gland, results in the production of excessive levels of the hormone cortisol. A study published in the Sept. 1, 2012 issue of the Journal of Clinical Endocrinology & Metabolism suggests that it increases the likelihood of impaired cognitive function and attentional deficits, even when the disease is in remission.
- Hypothyroidism, or low thyroid function, can cause impairment of memory and mental processes.
Sleep disorders: OSA, restless legs syndrome, and other sleep disorders can disrupt the storage of long-term memories that occurs during sleep, lead to problems with recall and attention, and cause fatigue that impairs optimal mental functioning.
Cardiovascular disease: These disorders negatively affect the flow of blood to brain tissues. They include:
- Vascular dementia, caused by diseases of the cerebral blood vessels, is the second most common form of dementia after AD.
- Small vessel disease, which involves the thickening and inflammation of brain blood vessels, triggers changes in brain tissue associated with cognitive impairment.
- High blood pressure may damage blood vessels and cause small bleeds in the brain that injure or kill neurons and impair cognition.
- High cholesterol levels contribute to a buildup of fatty deposits in cerebral blood vessels that impairs circulation and reduces the flow of oxygen and nutrients to neurons.
- Atrial fibrillation, or irregular heartbeat, results in higher risk for the formation of blood clots that can move to the brain and cause strokes that produce problems with memory, learning, attention, decision-making, or other abilities.
- Congestive heart failure may lead to lower oxygen levels that can negatively affect brain function.
Kidney and liver problems: Disorders of the kidneys or liver are often accompanied by cognitive problems, such as confusion and difficulties with memory. One recent study found that kidney disease increased risk for cognitive problems by 23 percent. Liver ailments may be accompanied by problems with thinking, attention, and information processing.
Other conditions: A number of other health problems—including vitamin B-12 deficiency, brain tumors, stroke, Parkinson’s disease, and infections such as encephalitis and meningitis—are linked to risk for impaired cognition.
If you have had a thorough checkup and the cause of your cognitive problems is not clear, Dr. Manoach recommends requesting a referral to a neuropsychologist, behavioral neurologist, or other memory specialist for further evaluation.