Lifestyle Factors - Causes Of Memory Impairment: Improving Memory Understanding Age Related Memory Loss

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Lifestyle factors

The way you live, what you eat and drink, and how you treat your body can also affect memory.

Alcohol use

Excessive alcohol use increases the risk for memory loss and dementia. People with alcoholism have difficulty performing short-term memory tasks, such as memorizing lists. Although the ability to remember usually declines gradually over years of heavy drinking, it can also occur suddenly and dramatically in a condition called Korsakoff's syndrome. This condition results from long-term vitamin B₁ (thiamine) deficiency combined with the toxic effects of alcohol on the brain. The memory loss of Korsakoff's syndrome is usually permanent, but other alcohol-related memory problems may be reversible if the person cuts down on drinking.

Moderate drinking, on the other hand, may actually reduce the risk of dementia. In a 2003 study in the Journal of the American Medical Association, people over age 65 who took up to one drink a day had roughly half the risk of Alzheimer's disease compared with people who didn't drink. Heavier drinkers had a 22% higher risk than did the nondrinkers. More recent studies, including 2005 data from WHIMS, continue to support an association between mild to moderate alcohol use and better cognitive function. It's not clear whether the type of alcohol — wine, beer, or hard liquor — makes any difference; studies have had conflicting results on this question. Some researchers think that the benefit from moderate alcohol may not be physiological; rather, moderate drinking may be a characteristic of people who are inherently in better health, are more social, and have a higher general level of cognitive performance.

Clearly, many questions remain about the relationship between alcohol and memory. Therefore, experts don't recommend moderate drinking as a hedge against dementia, but they do recommend against heavy drinking as one way to preserve your memory.

Diet

For years, scientists have believed that diet might influence the risk of age-related memory loss as well as dementia. Fat and cholesterol were considered possible risk factors, and several antioxidants and other nutrients were considered potentially protective. Studies have confirmed some dietary links and cast doubt on others.

B vitamins. There is strong evidence that this class of vitamins, which includes folic acid and vitamins B₆ and B₁₂, helps guard against age-related memory loss and dementia. People with deficiencies in any of the B vitamins are more likely to develop these problems. B vitamins are found in many foods, including whole-grain cereals, rice, nuts, milk, eggs, meats, liver, fish, fruits, and leafy green vegetables. The recommended daily intake for adults is 400 micrograms (mcg) of folic acid, 1.3–1.7 mg of vitamin B₆, and 2.4 mcg of vitamin B₁₂. Recommended intake levels are slightly higher for women during pregnancy or who are breast-feeding.

The B vitamins seem to have two beneficial effects on memory. Vitamin B₁₂ helps to make and preserve myelin, the protective sheath that surrounds axons, the filament-like projections from neurons that transmit signals to other neurons. Vitamin B₁₂ deficiency can cause permanent damage to neurons, impairing memory and overall ability to think, as well as making you feel fatigued.

B vitamins may also support memory by helping to moderate homocysteine, an amino acid in the blood that, in high levels, is considered a significant risk factor for cardiovascular disease and dementia, including Alzheimer's disease. The B vitamins break down homocysteine in the blood. Deficiencies of these vitamins cause elevated homocysteine.

You can have your homocysteine levels measured by a blood test in your doctor's office. There is no officially designated "normal" level, but research suggests that readings below 12 micromoles per liter are desirable. A study in the Annals of Neurology in 2003 found that people whose homocysteine levels were higher than 15 had three times the risk of cognitive decline over a three-year period as people with lower levels.

Getting the recommended amounts of the B vitamins, either through diet or supplements, can lower homocysteine. Keeping homocysteine low seems to help prevent cognitive decline, including memory loss. But whether taking B vitamins can restore lost memory function is unknown.

It is also unclear whether taking supplements above the recommended levels can offer additional protection against memory loss, but one study suggests the possibility. The study, reported by Dutch researchers at the 2005 International Conference on Prevention of Dementia, included 818 healthy people ages 50–75. It found that those who took high doses of folic acid (800 mcg) had less age-related memory loss over the course of three years than did people in a comparable group who took a placebo. Their scores on memory tests were on a par with those of people five years younger.

Fats. With regard to fats, it's not the amount of overall fat you eat but the type of fat that may increase your risk of Alzheimer's disease. A report in Archives of Neurology in 2003 found that eating large amounts of saturated fats (found primarily in meat, butter, and other dairy products) and trans fats (found mostly in processed foods with partially hydrogenated oils) increased the risk of Alzheimer's disease, whereas eating large amounts of unsaturated fats — including most vegetable oils and fish oils — decreased risk.

Antioxidants. Research findings regarding antioxidants are mixed. There's some evidence that vitamin E might slow age-related memory loss and that vitamins C and E might prevent certain forms of dementia. However, studies have not found any association between other antioxidants and the risk of Alzheimer's disease, and vitamin E may carry some health risks (see "Consider taking vitamins").

Some evidence suggests that an antioxidant in green tea called epigallocatechin-3-gallate, or EGCG, may help prevent Alzheimer's disease. A preliminary study on mice, published in the Journal of Neuroscience in 2005, found EGCG injections reduced production of beta-amyloid, a protein that accumulates in the brain and causes the neuronal degeneration of Alzheimer's disease. More research is needed to determine if there is benefit to humans.

Lack of intellectual stimulation

Over time, people who don't challenge their minds exhibit a greater degree of memory decline compared with people who remain mentally active. The landmark MacArthur Foundation Study on Successful Aging found that education level was the strongest predictor of mental capacity as people aged. A 2005 study in the Journal of Gerontology: Psychological Sciences reported that people who held jobs that involved complex work, such as speaking to, instructing, or negotiating with people, had a lower risk of dementia than people whose jobs were less intellectually demanding.

Most experts think it's not the years of formal education or the type of occupation per se that benefits memory. Instead, a lifelong habit of learning and engaging in mentally challenging activities — like reading, playing chess, performing music, or acquiring new skills — is thought to help keep the brain in shape.

Scientists believe that intellectual enrichment and learning stimulate the brain to make more connections, increasing the density of synapses. As a result, the "educated brain" may possess greater reserves of cognitive ability — a deeper well, so to speak — and be able to sustain more neuronal loss. Researchers refer to this enhancement of skills or abilities as cognitive reserve. In addition to increasing neuronal connections, mental activity sets into motion a host of processes that keep neurons and their interconnections alive and well.

Sedentary lifestyle

Insufficient physical exercise also increases the likelihood of memory impairment. The MacArthur study researchers were surprised to find that sedentary people had greater memory declines compared with people who were physically active on a regular basis. The active people didn't necessarily work out at a gym, but they did engage in significantly more routine physical activity such as climbing the stairs at home or taking walks in the neighborhood.

A Swedish study of 1,500 people ages 65–79, published in Lancet Neurology in 2005, found that those who participated in a physical activity at least twice a week were 60% less likely to develop Alzheimer's disease and half as likely to develop any form of dementia compared with sedentary people.

Some tantalizing explanations for the link between physical activity and memory come from animal research. A study in The Journal of Neuroscience in 2005 suggested that exercising may reverse some of the neuron loss that occurs with age. In the study, old mice that ran on a wheel added up to 50% more neurons than young, sedentary mice. The active older mice were able to learn new tasks better than sedentary older mice. Earlier, a MacArthur laboratory study on rats found that higher levels of exercise were associated with higher levels of nerve growth factor, a chemical essential for maintaining neurons as well as for protecting them after a stroke or other injury.

Some researchers speculate that exercise may benefit the brain directly by increasing blood supply to neurons, increasing the number of connections among neurons, and enhancing neurotransmitter function. Exercise may also benefit memory indirectly by keeping the lungs healthy and delivering a steady supply of oxygen to the brain. The MacArthur researchers found that good lung function was one characteristic of elderly people whose memories and other mental faculties remained strongest.

Lack of sleep

People who don't sleep well at night tend to be more forgetful than people who sleep soundly. A good night's sleep is essential for consolidating memories. Although people vary in their need for sleep, six hours may be the minimum that you need to ensure adequate daytime alertness and memory function.

A Harvard study, for example, suggested that getting at least six hours of sleep at night improves the ability to learn new skills. In the study, which required college students to learn a new computer game, researchers found that participants who had at least six hours of sleep the night before performed better than students who got less than six hours of sleep. And the students who did the best were the ones who had slept for eight hours.

According to one leading theory, sleep is important for memory because in sleep the brain replays information learned during the day, and in so doing, strengthens the neuronal connections that store this information. Building on earlier research on sleep and memory, a 2003 study in Proceedings of the National Academy of Sciences examined the pattern of brain activity in sleeping rats and found a volley of activity between the hippocampus and the cortex. The replaying of information and "cross-talk" between the hippocampus and cortex constitutes the process of memory consolidation.

Sleep may aid memory in another way as well — by decreasing levels of stress hormones. Stress hormones can interfere with memory formation by damaging the hippocampus. But stress hormones decline during the first few hours of sleep. Experts think that by suppressing stress hormones, sleep frees up the hippocampus to consolidate memories.

Stress

Several studies link stress to memory loss. The key here is not the minor stresses of daily life, like deadline pressures or petty arguments, but rather a profoundly traumatic event or an ongoing sense of extreme anxiety. These severe forms of stress may impair a person's memory. Brain-imaging studies of individuals who had experienced extreme stress — for example, veterans of the Vietnam War diagnosed with post-traumatic stress disorder — show that in such individuals, the volume of the hippocampus is smaller than usual.

Through animal research, scientists have discovered that neurons in the hippocampus are damaged by cortisol, a hormone released during stressful "fight or flight" types of situations. One study implicated cortisol in memory dysfunction in humans as well. In the study, a group of healthy adults received daily low-dose treatments of cortisol over the course of four consecutive days — about the amount that would be released under everyday stress. Another group received high doses over the same period of time. All participants took a test in which they listened to stories and then had to remember details about them immediately and 30 minutes later. People who had received the higher cortisol dose remembered less, both immediately and later, than people receiving the lower dose.

The memory dysfunction induced by this four-day experiment was reversible; once the cortisol wore off, the participants' memories returned to normal. No one knows how many days, weeks, months, or years of high-level stress it takes to cause irreversible memory impairment. What we do know is that a stressful event will cause some people to react more intensely than others, and it is this stress reaction that does the damage. To that extent, people may be able to control the harm that stress does to the memory by trying to modify their exposure and responses to stressful life events.

One way to reduce stress is to work on gaining a greater sense of control over your life. The MacArthur Foundation's study on aging found that the people who reported the most "self-efficacy," or mastery, also had the best memory in old age. The researchers viewed self-efficacy as a buffer against the feeling of helplessness that often contributes to stress.

Smoking

Smokers have a greater degree of age-related memory loss and other memory problems than nonsmokers. Research shows that they're less adept at recalling names and faces. A 2003 British study reported that the verbal memory function of people ages 43–53 was weaker in the smokers than in the nonsmokers. A 2004 study published in Neurology tracked the memory of 9,209 people ages 65 and older annually for several years by giving them the Mini-Mental State Examination, a standard test of cognitive functions. Nearly everyone's score dropped during this period, but the decline was five times greater for smokers than for people who never smoked.

It is understandable that smoking would impair memory. Smoking increases the risk of cerebrovascular disease, which itself is a risk factor for memory loss. It harms the lungs, and good lung function is essential for good memory function. Smoking can also deprive the brain of oxygen by narrowing blood vessels. Smoking is especially common among people who are depressed, and depression also undermines memory. Finally, smoking may harm memory by compromising your diet — smokers tend to consume lower levels of antioxidants and have higher cholesterol and triglycerides.

Illicit drug use

People who use marijuana, cocaine, and ecstasy have problems with memory and related cognitive functions — not only while they are under the influence, but also for weeks after the drugs' effects wear off.

A study in Neurology in 2002 found that people who had smoked marijuana heavily for several years scored lower than nonusers on tests of attention, short-term memory, and learning. These deficiencies persisted even after the people abstained from marijuana for a month. Marijuana's active chemical — the Delta (9)-tetrahydrocannabinol molecule — causes its psychoactive effect by attaching to receptors in brain regions vital for memory formation, including the hippocampus, amygdala, and cortex.

Habitual users of ecstasy, or 3,4-methylenedioxymethamphetamine (MDMA), have difficulty forming and recalling long-term memories. This problem was 23% more common among ecstasy users than nonusers in a survey of 763 people published in the Journal of Psychopharmacology in 2004. Ecstasy use depletes levels of serotonin and dopamine, neurotransmitters that are essential for memory.

Memory impairment is also a side effect of habitual cocaine use. Cocaine users score lower than nonusers on tests of working memory and recall of long-term memories. Deficits are apparent on tests of verbal memory, even after users have abstained from cocaine for 45 days.

One of the worst things you can do to your memory is to use illicit drugs. It is unclear how much of the memory impairment can be restored by quitting, but at the very least, quitting can prevent further damage.

Toxic exposure

Lead, mercury, and other chemicals present in homes and workplaces can cause memory loss and poor concentration. Lead poisoning can result from drinking contaminated tap water and breathing in lead dust generated by the deterioration of lead paint in homes built before 1978, when it was outlawed. Carbon monoxide fumes leak from malfunctioning household furnaces and are spewed from automobile exhaust systems. Mercury and other toxic substances are found in some paints, dyes, and inks used in artwork. Still other sources of toxic exposure are pesticides used in home gardens and farms, darkroom chemicals, and chemicals used in metalwork and woodwork.

You can reduce your exposure to toxic substances by taking the following precautions. Before using paints, solvents, and pesticides, read the labels for safe handling. Test your home water supply and use a water filter to eliminate lead, if necessary. Avoid sanding, scraping, and otherwise disrupting lead paint on older homes. If you do plan to remove lead paint, use a government-approved contractor for this work. Have your car and furnace serviced regularly to minimize carbon monoxide emissions.

Last updated:	January 23, 2007