Mild memory impairment is associated with aging, but there are many other causes for unusual forgetfulness. Medications, toxic substances, lifestyle factors, family history, injuries, and a variety of diseases and conditions can affect the memory. Determining the cause of a patient's memory loss can shed light on whether the problem is likely to be temporary or permanent and, in many situations, can suggest treatment or prevention of further damage.
Alzheimer's Disease
Alzheimer's disease is a progressive, neurodegenerative disease that destroys a person's memory and ability to learn, reason, communicate and carry out daily activities. The disease affects as many as 5.3 million Americans, according to the Alzheimer's Association, and accounts for 50 to 80 percent of all dementia cases in elderly people.
Depression
According to the AARP, depression can be a cause as well as an effect of memory dysfunction. Severe, ongoing, and untreated depression--particularly in the elderly--can make people forgetful by interfering with the ability to concentrate and process information.
Neurological Disorders
When neurons are damaged or cannot function effectively, memory impairment and cognitive decline can occur. Among the many illnesses that interfere with brain activities---including memory---are Parkinson's disease, multiple sclerosis, epilepsy, brain tumors, Lyme disease that affects the brain and nervous system, Huntington's disease, and Creutzfeldt-Jakob disease, according to the U.S. Food and Drug Administration.
Infections
Memory problems can occur in people with infections of the lining or substance of the brain, including HIV, encephalitis, tuberculosis, syphilis and herpes.
Heart-Related Diseases
Conditions that have been linked with heart disease--high blood pressure, high cholesterol and diabetes--have also been associated with memory problems. Hypertension appears to impair memory by damaging the brain's white matter, which can occur fairly quickly after the disease develops. High cholesterol appears to increase the risk for mild cognitive impairment and Alzheimer's disease, but the memory loss occurs many years after the condition occurs. High blood sugar damages the small blood vessels in the brain and depresses the function of the hippocampus, leading to a 50 to 100 percent higher risk in diabetics of developing Alzheimer's disease, according to the AARP.
Thyroid Dysfunction
When the thyroid doesn't function properly, metabolism runs too fast or too slow, interfering with memory and learning. Hyperthyroidism, which causes an abnormally fast metabolism, can make people feel confused. Hypothyroidism, which causes an abnormally slow metabolism, can make people feel sluggish, sleepy and depressed.
Obstructive Sleep Apnea
Sleep helps to consolidate memories and reduces the level of stress hormones, the FDA says, so any condition that interferes with a good night's sleep will affect the memory. Obstructive sleep apnea causes the patient to awaken hundreds of times a night by interrupting breathing, resulting in sleep deprivation.
