Age-Related Cognitive Decline
A decline in memory and cognitive (thinking) function is considered by many authorities to be a normal consequence of aging.1 2 While age-related cognitive decline (ARCD) is therefore not considered a disease, authorities differ on whether ARCD is in part related to Alzheimer’s disease and other forms of dementia3 or whether it is a distinct entity.4 5 People with ARCD experience deterioration in memory and learning, attention and concentration, thinking, use of language, and other mental functions.6 7
ARCD usually occurs gradually. Sudden cognitive decline is not a part of normal aging. When people develop an illness such as Alzheimer’s disease, mental deterioration usually happens quickly. In contrast, cognitive performance in elderly adults normally remains stable over many years, with only slight declines in short-term memory and reaction times.8
People sometimes believe they are having memory problems when there are no actual decreases in memory performance.9 Therefore, assessment of cognitive function requires specialized professional evaluation. Psychologists and psychiatrists employ sophisticated cognitive testing methods to detect and accurately measure the severity of cognitive decline.10 11 12 13 A qualified health professional should be consulted if memory impairment is suspected.
Some older people have greater memory and cognitive difficulties than do those undergoing normal aging, but their symptoms are not so severe as to justify a diagnosis of Alzheimer’s disease. Some of these people go on to develop Alzheimer’s disease; others do not. Authorities have suggested several terms for this middle category, including “mild cognitive impairment”14 and “mild neurocognitive disorder."15 Risk factors for ARCD include advancing age, female gender, prior heart attack, and heart failure.
What are the symptoms of age-related cognitive decline?
People with ARCD experience deterioration in memory and learning, attention and concentration, thinking, use of language, and other mental functions.
Dietary changes that may be helpful for age-related cognitive decline
In the elderly population of southern Italy, which eats a typical Mediterranean diet, high intake of monounsaturated fatty acids (e.g., olive oil) has been associated with protection against ARCD in preliminary research.16 However, the monounsaturated fatty acid content of this diet might only be a marker for some other dietary or lifestyle component responsible for a low risk of ARCD.
Caffeine may improve cognitive performance. Higher levels of coffee consumption were associated with improved cognitive performance in elderly British people in a preliminary study.17 Older people appeared to be more susceptible to the performance-improving effects of caffeine than were younger people. Similar but weaker associations were found for tea consumption. These associations have not yet been studied in clinical trials.
Animal studies suggest that diets high in antioxidant-rich foods, such as spinach and strawberries, may be beneficial in slowing ARCD.18 Among people aged 65 and older, higher vitamin C and beta-carotene levels in the blood have been associated with better memory performance,19 though these nutrients may only be markers for other dietary factors responsible for protection against cognitive disorders.
One preliminary study found that, among middle-aged men, those who ate more tofu had a higher rate of cognitive decline compared with men who ate less tofu.20 Since tofu and other soy products have consistently demonstrated important health benefits in this age group (e.g., as cholesterol-lowering foods), middle-aged men should not limit their consumption of these foods until the results of this isolated study are independently confirmed.
Lifestyle changes that may be helpful for age-related cognitive decline
Cigarette smokers and people with high levels of education appear to have some protection against ARCD.21 The reason for each of these associations remains unknown. However, as cigarette smoking generally is not associated with other health benefits and results in serious health risks, doctors recommend abstinence from smoking, even by people at risk of ARCD.
A large, preliminary study in 1998 found associations between hypertension and deterioration in mental function.22 Research is needed to determine if lowering blood pressure is effective for preventing ARCD.
A randomized, controlled trial determined that group exercise has beneficial effects on physiological and cognitive functioning, and well-being in older people. At the end of the trial, the exercisers showed significant improvements in reaction time, memory span, and measures of well-being when compared with controls.23 Going for walks may be enough to modify the usual age-related decline in reaction time. Faster reaction times were associated with walking exercise in a British study.24 The results of these two studies suggest a possible role for exercise in preventing ARCD. However, controlled trials in people with ARCD are needed to confirm these observations.
Psychological counseling and training to improve memory have produced improvements in cognitive function in persons with ARCD.25 26 27
Nutritional supplements that may be helpful for age-related cognitive decline
Several clinical trials suggest that acetyl-L-carnitine delays onset of ARCD and improves overall cognitive function in the elderly. In a controlled clinical trial, acetyl-L-carnitine was given to elderly people with mild cognitive impairment. After 45 days of acetyl-L-carnitine supplementation at 1,500 mg per day, significant improvements in cognitive function (especially memory) were observed.28 Another large trial of acetyl-L-carnitine for mild cognitive impairment in the elderly found that 1,500 mg per day for 90 days significantly improved memory, mood, and responses to stress. The favorable effects persisted at least 30 days after treatment was discontinued.29 Controlled30 31 32 and uncontrolled33 clinical trials on acetyl-L-carnitine corroborate these findings.
Phosphatidylserine derived from bovine brain phospholipids has been shown to improve memory, cognition, and mood in the elderly in at least two placebo-controlled trials. In both trials, geriatric patients received 300 mg per day of phosphatidylserine or placebo. In an unblinded trial of ten elderly women with depressive disorders, supplementation with phosphatidylserine produced consistent improvement in depressive symptoms, memory, and behavior after 30 days of treatment.34 A double-blind trial of 494 geriatric patients with cognitive impairment found that 300 mg per day of phosphatidylserine produced significant improvements in behavioral and cognitive parameters after three months and again after six months.35
A double-blind trial found both 30 mg and 60 mg per day of vinpocetine improved symptoms of dementia in patients with various brain diseases.36 Another double-blind trial gave 30 mg per day of vinpocetine for one month, followed by 15 mg per day for an additional two months, to people with dementia associated with hardening of the arteries of the brain, and significant improvement in several measures of memory and other cognitive functions was reported.37 Other double-blind trials have reported similar effects of vinpocetine in people with some types of dementia or age-related cognitive decline.38 39 However, a study of Alzheimer patients in the United States found vinpocetine given in increasing amounts from 30 mg to 60 mg per day over the course of a year neither reversed nor slowed the decline in brain function measured by a number of different tests.40
Vincamine, the unmodified compound found naturally in Vinca minor, has also been tested in people with dementia. A large double-blind trial found 60 mg per day of vincamine was more effective than placebo for improving several measures of cognitive function in patients with either Alzheimer’s disease or dementia associated with vascular brain disease.41 A small double-blind study of vascular dementia also reported benefits using 80 mg per day of vincamine.
Vitamin B6 (pyridoxine) deficiency is common among people over age 65.42 A Finnish study demonstrated that approximately 25% of Finnish and Dutch elderly people are deficient in vitamin B6 as compared to younger adults. In a double-blind trial, correcting this deficiency with 2 mg of pyridoxine per day resulted in small psychological improvements in the elderly group. However, the study found no direct correlation between amounts of vitamin B6 in the cells or blood and psychological parameters.43 A more recent double-blind trial of 38 healthy men, aged 70 to 79 years, showed that 20 mg pyridoxine per day improved memory performance, especially long-term memory.44
Supplementation with vitamin B12 may improve cognitive function in elderly people who have been diagnosed with a B12 deficiency. Such a deficiency in older people is not uncommon. In a preliminary trial, intramuscular injections of 1,000 mcg of vitamin B12 were given once per day for a week, then weekly for a month, then monthly thereafter for 6 to 12 months. Researchers noted “striking” improvements in cognitive function among 22 elderly people with vitamin B12 deficiency and cognitive decline.45 Cognitive disorders due to vitamin B12 deficiency may also occur in people who do not exhibit the anemia that often accompanies vitamin B12 deficiency. For example, in a study of 141 elderly people with cognitive abnormalities due to B12 deficiency, 28% had no anemia. All participants were given intramuscular injections of vitamin B12, and all showed subsequent improvement in cognitive function.46
Vitamin B12 injections put more B12 into the body than is achievable with absorption from oral supplementation. Therefore, it is unclear whether the improvements in cognitive function described above were due simply to correcting the B12 deficiency or to a therapeutic effect of the higher levels of vitamin B12 obtained through injection. Elderly people with ARCD should be evaluated by a healthcare professional to see if they have a B12 deficiency. If a deficiency is present, the best way to proceed would be initially to receive vitamin B12 injections. If the injections result in cognitive improvement, some doctors would then recommend an experimental trial with high amounts of oral B12, despite a current lack of scientific evidence. If oral vitamin B12 is found to be less effective than B12 shots, the appropriate treatment would be to revert to injectable B12. At present, no research trials support the use of any vitamin B12 supplementation in people who suffer from ARCD but are not specifically deficient in vitamin B12.
Melatonin is a hormone secreted by the pineal gland in the brain. It is partially responsible for regulating sleep-wake cycles. Cognitive function is linked to adequate sleep and normal sleep-wake cycles. Cognitive benefits from melatonin supplementation have been suggested by preliminary research in a variety of situations and may derive from the ability of melatonin to prevent sleep disruptions.47 48 49 50 A double-blind trial of ten elderly patients with mild cognitive impairment showed that 6 mg of melatonin taken two hours before bedtime significantly improved sleep, mood, and memory, including the ability to remember previously learned items.51 However, in a double-blind case study of one healthy person, 1.6 mg of melatonin had no immediate effect on cognitive performance.52
The long-term effects of regularly taking melatonin supplements remain unknown, and many healthcare practitioners recommend that people take no more than 3 mg per evening. A doctor familiar with the use of melatonin should supervise people who wish to take it regularly.
Use of vitamin C or vitamin E supplements, or both, has been associated with better cognitive function and a reduced risk of certain forms of dementia (not including Alzheimer’s disease).53 Clinical trials of these antioxidants are needed to confirm the possible benefits suggested by this study.
Are there any side effects or interactions with age-related cognitive decline?
Refer to the individual supplement for information about any side effects or interactions.
Herbs that may be helpful for age-related cognitive decline
Most54 55 56 57 58 59 60 but not all61 clinical trials, many of them double-blind, have found ginkgo supplementation to be a safe and effective treatment for ARCD.
Huperzine A, an isolated alkaloid from the Chinese medicinal herb huperzia(Huperzia serrata), has been found to improve cognitive function in elderly people with memory disorders. One double-blind trial found that huperzine A (100 to 150 mcg two to three times per day for four to six weeks) was more effective for improving minor memory loss associated with ARCD than the drug piracetam.62 More research is needed before the usefulness of huperzine A is confirmed for mild memory loss associated with ARCD.
Are there any side effects or interactions with age-related cognitive decline?
Refer to the individual herb for information about any side effects or interactions.