Exercising the Brain to Avoid Cognitive Decline

Examining the Evidence

William E Reichman; Alexandra J Fiocco; Nathan S Rose

Aging Health. 2010;6(5):565-584.

Abstract and Introduction

Abstract

Dementias and related cognitive disorders of the brain are strongly age-associated and prevalence is expected to rise dramatically with a rapidly aging population. As a result, there has been increasing attention on the prevention and treatment of cognitive decline associated with these conditions. A number of approaches have been designed to maintain and strengthen the cognitive capacity of the healthy, as well as the pathologically damaged brain. Evidence suggests that despite advancing age, our brains, and thus our cognitive functions, retain the ability to be maintained and strengthened through the biological process of neuroplasticity. With this opportunity, a new commercial field of 'brain fitness' has been launched to bring to the market training exercises and games that maintain and strengthen cognitive abilities in adulthood. However, the majority of brain fitness methods and products now marketed and sold to consumers have scant scientific evidence to support their effectiveness.

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Table 1. Description of various cognitive domains and associated effects of age in adulthood.
Domain	Description	Example	Common measures	Effects of age	Cf/Gf
*Memory*
Declarative	The ability of a person to 'declare' or recite evidence of memory ability
– Episodic memory	Recalling information about prior experiences, events and episodes	Recalling the details of recent conversations or where you placed your keys yesterday	CVLT, logical memory	↓^†	Gf
– Semantic memory	Knowledge, facts and meanings	Recalling facts or the name of familiar persons	NART, vocabulary tests	= (possibly ↑) (↓for semantic dementia)	Cf
– Prospective memory	Remembering to perform intended actions at the appropriate moment in the future; 'remembering to remember'	Remembering to take medication or attend upcoming appointments	McDaniel and Einstein paradigm, virtual week	↓ (laboratory-based tasks) = (possibly ↑ for real-world tasks)
– Working memory	Temporary maintenance and manipulation of information	Maintaining a phone number or mental arithmetic	Digit span, reading span, n-back or corsi blocks	= primary/short-term ↓ working memory, especially visuospatial	Gf
Nondeclarative	Tacit knowledge or lack of awareness
– Procedural memory	Motor memory	How to ride a bike or play piano	Pursuit rotor task, serial reaction time task, mirror tracing task or weather prediction task	=
– Implicit memory	Behavior affected by the past with awareness	Read words (bone) and then complete word fragment (b_n_) with first word that comes to mind	Priming	=	Cf
*Attention*
Selective attention	Focusing on relevant information; ignoring irrelevant information	Listening to your friend and not the person at the next table	Cocktail party effect; reading with distraction	↓
Vigilance	Concentration, focusing on relevant information and ignoring irrelevant information for extended periods of time	Monitoring the gas gauge or cookies in the oven	Continuous performance task	↓
Divided attention	Performing or switching between two tasks at the same time	Driving while conversing; performing a memory or attention task while monitoring digits	Dual-task paradigms (e.g., remember words, monitor for two odd digits presented in succession)	↓
*Processing speed*
Psychomotor speed	Motor or physical response	Press a button when a stimulus appears	Simple choice reaction time	↓
Information processing	Processing information and making decisions as fast and as accurately as possible	Press yes if the letter string is a real word or no if it is a nonword	Lexical decision, mental rotation or enumeration	↓ (i.e., 'general slowing'), especially visuospatial	Gf
*Executive functions*
Planning	Plan, organize, initiate and sequence activities in the performance of a complex task	Organizing a series of steps to pick up items from grocery store	Tower of Hanoi	↓	Gf
Mental flexibility	Rapidly shift or change an approach to a task as the situation demands	Playing complex video games (e.g., first-person shooters)	Wisconsin card sort	↓	Gf
Reasoning	Higher order strategy and conceptual formulation, information manipulation and abstract thinking	Understanding analogies; solving problems	Raven's matrices	↓	Gf
Inhibition	Interference or conflict resolution or withholding an inappropriate response	Resisting dessert when trying to lose weight	Stroop test	↓	Gf
*language/visuospatial abilities*
Language (verbal) abilities	Both expressive and receptive components and the ability to write and read	Read a book, write about it or talk about it	NART, vocabulary, reading comprehension	= (possibly ↑)	Cf
Visuospatial abilities	Mental imagery, mental rotation, distance judgments or spatial/directional relations	Driving	Drawing, copying, assembling block designs, Hooper Visual Organization test	↓	Gf

Cf and Gf reflect tasks or abilities thought to capture Cf and Gf, respectively, and are only included for those domains that clearly fall into one or the other category.
^†Declines may be explained by undiagnosed preclinical dementia [78].
Cf: Crystallized intelligence; CVLT: California verbal learning test; Gf: Fluid intelligence; NART: National adult reading test.

Table 2. Epidemiological studies that assess the association between lifestyle factors and cognitive function in late life.
Study	Sample size (n)	Lifestyle factors assessed	Statistically controlled factors	Follow-up (years)	Significant factors	Generalization outcome measures	Ref.
Verghese et al.	469 healthy older adults	Cognitive activity, physical activity	Age, sex, education, physical morbidity and baseline cognitive status	5	Leisure factors (reading, playing games, musical instruments or dancing)	Reduced risk of dementia	[34]
Karp et al.	931 healthy older adults	Occupation complexity, social engagement	Education	6	More complex work and engagement with people	Reduced progression to dementia^†	[35]
Wilson et al.	801 healthy older adults	Cognitive activity (e.g., reading and playing games)	Age, sex, education and baseline cognitive status	4.5	Cognitive activity (e.g., reading and playing games)	Reduced cognitive decline and progression to dementia	[36]
Wilson et al.	4000 adults	Cognitive activity (e.g., reading and playing games)	Baseline level of cognition, age, sex, race and education	5.3	Cognitive activity (e.g., reading and playing games)	Reduced cognitive decline (e.g., episodic memory, immediate and delayed recall or perceptual speed and the MMSE)	[37]
Fritsch et al.	809 adults (including 264 surrogates of AD patients)	Mental leisure activities (novelty seeking, exchange of ideas and social activity)	Age, gender, ethnicity, education and occupation	–^‡	Novelty seeking, exchange of ideas	Reduced risk of dementia	[38]
Helzner et al.	283 AD patients	Leisure activity	Age, sex, ethnicity, education and baseline IQ	5	Intellectual activity	Higher baseline cognitive status, fewer physical comorbidity (including stroke), but faster decline postdiagnosis	[39]

^†Effects were positive, but no longer significant after statistically controlling for education.
^‡Data not available: a case–control method with logistic regression was used.
AD: Alzheimer's disease; MMSE: Mini-mental status exam.

Table 3. Case–control studies that assess the effects of cognitive training on cognitive function in older adults.
Study	Sample size (n)	Cognitive training	Control condition	Duration (min/week)	Total sessions (n)	Follow-up (months)	Significant training and near transfer effects	Significant far transfer effects	Ref.
Ball et al. (ACTIVE)	2832 healthy older adults randomly assigned	Three training groups: memory strategy, reasoning and computerized speed of processing	No contact	120–150	10	24	Domain of targeted training	ADL, IADL and driving habits questionnaire	[48]
Willis et al. (ACTIVE)	67% of original sample	See above	See above	See above	See above	72	Domain of targeted training	IADL	[46]
Smith et al. (IMPACT)	487 healthy older adults	Auditory information processing (Posit Science, CA, USA)	Active	300	40–50	8 weeks	Attention, episodic memory, visuospatial abilities	Auditory memory and attention	[51]
Mahncke et al. (IMPACT)	182 healthy older adults	Auditory information processing (Posit Science)	Active contact and no contact	240	40	3	Attention, episodic memory, visuospatial abilities	Not reported	[50]
Engviv et al.	22 healthy older adults	Memory strategy (method of loci)	No contact	60	8	2	Word recognition and source memory	Volumetric changes in structural MRI	[52]
Kurz et al.	18 MCI and 10 AD patients	Activity planning, self-assertiveness training, relaxation techniques, stress management, use of external memory aids, memory training and motor exercise	Wait list	1320	20	1	Verbal and nonverbal episodic memory in MCI; no change in AD	ADL and mood in MCI; no change in AD	[53]
Troyer et al.	50 MCI patients	Memory strategy training (spaced retrieval, memory book, semantic association, logical location) within a larger mixed intervention	Wait list	25	10	3	Episodic recall, digit span and laboratory memory strategy use	Everyday memory strategy knowledge and use, multifactorial memory questionnaire	[54]
Belleville et al.	20 MCI patients	Memory strategy training	Wait list	120	8	2	Episodic recall of lists and face–name associations	Subjective memory and well-being	[55]
Barnes et al.	47 MCI patients	Auditory information processing (Posit Science)	Active	500	30	–	Attention, episodic memory, visuospatial abilities and verbal fluency	GDS	[79]
Rozzini et al.	59 MCI patients	Computerized training of attention, reasoning, visuospatial abilities with ChEI	No contact and ChEI alone	12	72	3	Memory, verbal fluency, Raven's matrices	MMSE, behavioral disturbances; depressive symptoms	[80]
Rapp et al.	19 MCI patients	Memory strategy training (cueing, categorization, chunking, method of loci) within a larger, multifaceted intervention	No contact	6	96	6	Memory functioning questionnaire, memory controllability questionnaire, episodic recall (words, stories, grocery lists, names and faces)	Profile of mood states	[81]
Requena et al.	86 AD patients	Computerized cognitive training with ChEI	Active	225	520	–	–	MMSE, GDS ADAS-Cog	[82]
Galante et al.	11 AD patients	Multidomain computer training, NPT	Active	180	12	9	Prose memory, word repetition test, Corsi blocks, Raven's matrices, digit cancellation, semantic and phonemic fluency, constructional and ideomotor apraxia	MMSE, NPI, GDS, IADL, basic ADL	[83]
Cahn-Weiner et al.	34 AD patients	Memory strategy training	Active	45	6	2	Verbal and visuospatial memory, verbal fluency, visuospatial processing speed	ADL	[84]
Loewenstein et al.	44 AD patients	Cognitive rehabilitation training	Active	90	24	3	Face–name association, orientation, object memory, change (for purchase), balancing checkbook, continuous performance test	MMSE, basic ADL, depression	[85]
Olazaran et al.	72 AD, 12 MCI patients	Multidomain training (pen and paper)	Active	60	103	12	–	MMSE, functional activities questionnaire, GDS ADAS-Cog	[86]
Davis et al.	37 AD patients	Memory strategy and attention training	Active	60	5	–	Logical memory test, visual reproduction test, digit span test, verbal series attention test and verbal fluency test	MMSE, quality of life assessment and GDS	[87]
Tarraga et al.	46 AD patients	Multidomain (attention, gnosis language, memory, orientation, calculation), internet-based program within a multifactorial intervention	Active	75	72	5.5	Verbal fluency and story recall	ADAS-Cog, MMSE, rapid disability rating scale-2 and GDS	[88]

ACTIVE: Advanced Cognitive Training for Independent and Vital Elderly; AD: Alzheimer's disease; ADAS-Cog: Alzheimer's disease assessment scale-cognitive subscale; ADL: Activities of daily living; ChEI: Cholinesterase inhibitors; GDS: Geriatric depression scale; IADL: Instrumental activities of daily living; MCI: Mild cognitive impairment; MMSE: Mini-mental status exam; NPI: Neuropsychiatry inventory.

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Executive Summary

Rationale behind brain exercise to avoid cognitive decline

The population is aging across the globe at an unprecedented rate.
The aging process is associated with a decline in certain cognitive functions in healthy elderly as well as an increased prevalence of more significant cognitive decline or dementia due to disorders such as Alzheimer's disease.
Adults appear to retain the ability to maintain and improve cognitive function through mid and late life through the innate biological process of neuroplasticity.

Aging-related cognitive decline

Normal aging is associated with changes in specific cognitive domains. Acquired information (vocabulary, knowledge and facts), often described as 'crystallized intelligence' is stable with age and may continue to improve over time.
The more dynamic abilities to problem solve, recall new information, manipulate data, and to do so with speed, sometimes described as 'fluid intelligence', may decline in the normal aging process.
A substantial number of older people will suffer pathological changes in cognition such as mild cognitive impairment and overt dementia, of which Alzheimer's disease and stroke are the most common causes.

Cognitive training strategies

A limited number of rigorously designed and well-controlled cognitive training programs have demonstrated benefit in improving domain-specific cognitive functions in healthy elderly and mild cognitive impairment patients.
Whether improvement in test performance as a result of domain-specific training is associated with significant improvement in day-to-day functioning in the activities of daily living remains nonconclusive and additional scientific study is required.

Brain fitness market

Despite the need for more rigorous studies to validate the efficacy of structured cognitive training programs, a rapidly growing commercial market of 'brain fitness' products targeted to consumers has developed. These involve web-based programs, games, executive training sessions and other modalities.

Future perspective

With an aging population across the globe, there will be growing interest in preserving brain and cognitive health through adulthood.
More scientific studies will need to be conducted to examine what cognitively stimulating activities, lifestyle choices, nutritional practices and health factors most positively impact brain health as we age.
Ultimately, we will think of 'brain fitness' in a similar fashion to how we now approach cardiovascular fitness. To maintain optimal cognitive function as one ages will likely require a combination of good health practices, a steady routine of cognitive and aerobic exercise, pursuing optimal nutrition and having active engagement in stimulating, novel and rewarding social and recreational activities.