Common Dietary Supplements for Cognitive Health

MK Gestuvo; WW Hung

Disclosures

Aging Health. 2012;8(1):89-97. 

In This Article

Abstract and Introduction

Abstract

Advancing age is a major risk factor for cognitive impairment and dementia. Currently, there are no effective preventive strategies for cognitive decline. Since physicians have no drug therapies to offer, patients and families may turn to complementary and alternative medicine to preserve cognition. Dietary supplements are one of the most common forms of complementary and alternative medicine that patients use and although limited, evidence for their potential interactions with other treatments has been documented. Considering the insufficient evidence for their efficacy, potential for interaction with other therapies and costs to patients, physicians should be aware of the use of dietary supplements among their patients so that they can advise their patients on the potential benefits and harms.

Introduction

Older adults aged 65 years of age and above currently account for 13% of the US population and this figure is expected to rise to 16% in 2020 and 20% in 2050.[101] As the population ages, the number of older adults suffering from age-related health problems, such as cognitive decline, is also expected to rise. A recent national survey estimated that the prevalence of cognitive impairment among noninstitutionalized older adults was 4% among the 65–74-year age group but rose to 9 and 20% in the 75–84 and 85 years and above age groups.[1] Other studies have estimated that the prevalence of mild cognitive impairment (MCI), which was defined as a self- or informant-reported cognitive complaint with evidence of impairment on objective cognitive testing but without functional dependency,[2,3] among older adults aged 65 years and over, to be between 7.7 and 23.4%.[2,4] On the other hand, the prevalence rate of Alzheimer's disease (AD), the most common cause of dementia, among older adults over 70 years of age is estimated to be 9.5%.[5] The incidence rate of AD increases with age, from 53 per 1000 adults aged 65–74 years, to 231 per 1000 adults 85 years old or older.[6] Other common chronic diseases have also been suggested to be associated with cognitive decline, including cerebrovascular disease, cardiovascular disease (CVD), hypertension, diabetes mellitus, chronic lung disease and kidney disease.[7–11] Cognitive impairment is thus prevalent and may lead to devastating consequences including disability, depression, institutionalization and poor quality of life.[12–17]

Given the high burden of cognitive impairment and its poor outcomes, it is not surprising that older adults consider that maintaining cognitive health is a key to aging well.[18] Also, since little is known of how healthy older adults can maintain intact cognitive function, it is not surprising that a large proportion of older adults use complementary and alternative medicine (CAM) for cognitive health. In a recent US national survey, almost four out of ten adults had used CAM in the previous 12 months.[19] In community-dwelling older adults, 52% of prescription medication users concurrently used dietary supplements, which are defined as products intended to supplement the diet but not intended to diagnose, treat, cure or prevent any disease, and contain one or more dietary ingredient including vitamins, minerals, herbs or other botanicals and amino acids.[20–22,102] In the USA, unlike drug products, dietary supplements are not subject to US FDA approval for safety or effectiveness before they are marketed to consumers.[102] Out-of-pocket costs on CAM were estimated at US$33.9 billion in the USA in 2007, with 44% on the purchase of nonvitamin and nonmineral natural products.[23] Owing to the potential for interactions with other treatments and costs to patients, physicians should be aware of the use of CAM among their patients so that they can advise their patients on the potential benefits and harms. Therefore, our objective is to review current evidence on the efficacy and harm of the most commonly used dietary supplements for cognitive health. Selected supplements were identified by a Medline® search for studies investigating dietary supplements most commonly used by the general population and older adults for cognition, memory or dementia.[20,21,24–26] For each dietary supplement a Medline search was performed limiting articles to those written in the English language and published since 1990. Search terms used included common and chemical names of each dietary supplement, 'cognition', 'cognitive impairment', 'memory', 'memory loss', 'dementia' and 'Alzheimer's disease'. Inclusion of articles was based on the level of evidence. When available, systematic reviews of randomized controlled trials and reports of randomized controlled trials were preferentially cited over observational studies.

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