Year : 2016 | Volume
: 3 | Issue : 1 | Page : 52--56
Prevention of cognitive decline: Lifestyle and other issues
Cyriac George, Shijin A Ummar, KS Shaji
Department of Psychiatry, Government Medical College, Thrissur, Kerala, India
Department of Psychiatry, Government Medical College, Thrissur, 680596, Kerala
Ageing often leads to decline in cognitive abilities. Significant cognitive impairment leads to functional impairment and need for care. Prevention of cognitive decline and delaying its progression would help to reduce the need for long-term care. Both genetic and environmental factors are important determinants of cognitive health in late life. A better cognitive reserve helps to prevent cognitive decline. Cognitive reserve is now considered as a functional reserve rather than a structural reserve. Cognitive reserve can be enhanced through experience. People with higher level of education tend to have higher cognitive reserve. Better cognitive reserve can act as a buffer. Engagement in cognitively stimulating activities may prevent cognitive decline in late life. Physical exercise also improves cognitive health. Aerobic exercises, which improve cardiorespiratory fitness, improve cognitive functions like motor functions, cognitive speed, and auditory and visual attention. Beneficial effects on executive functions are also reported. Healthy diet, especially adherence to Mediterranean diet (MeDi), is considered to be useful in preserving cognitive health. Engagement in social activities might also reduce cognitive decline. Encouraging adherence to a healthy lifestyle and continuing to be physically, socially, and cognitively active seems to be a promising strategy to prevent cognitive decline.
|How to cite this article:|
George C, Ummar SA, Shaji K S. Prevention of cognitive decline: Lifestyle and other issues.J Geriatr Ment Health 2016;3:52-56
|How to cite this URL:|
George C, Ummar SA, Shaji K S. Prevention of cognitive decline: Lifestyle and other issues. J Geriatr Ment Health [serial online] 2016 [cited 2019 Sep 23 ];3:52-56
Available from: http://www.jgmh.org/text.asp?2016/3/1/52/181917
The world population is ageing rapidly. Ageing leads to decline in physical and mental abilities. Many older people would experience significant decline in their cognitive abilities in late life. Ageing is often associated with visual and auditory impairment. However, most of the older adults are able to compensate and carry on because of intact cognitive functions. However, sensory impairments, when associated with cognitive impairment, leads to early dependency. Many of them would require more effort for activities of daily life, especially for carrying out instrumental activities of daily living (IADL). Further progression would lead to need for care and assistance. Medical conditions are common in late life. The capacity for self-care is especially important in the long-term management of medical conditions. Cognitive decline and the resultant disability can affect adherence to medical advice and can impact health outcomes.
With the increase in life expectancy, there will be more older people in their eighth and ninth decades. A significant proportion of them will experience cognitive decline and Would need care. The number of people with dementia is expected to double by 2030 and more than triple by 2050.  Informal care by the family is the major form of care for them. This is particularly so in the low- and middle-income countries (LMIC). Prevention of cognitive disorders is as important as the prevention of other lifestyle disorders.  This is an area which needs focused attention.
It is important to identify the modifiable risk factors for dementia and use this knowledge for prevention of cognitive decline. Both genetic and environmental factors influence cognitive decline in older adults. Cognitive impairment often leads to functional impairment. Comorbid medical illnesses add to the cognitive disability. The pathophysiological changes often begin well in advance, much before the onset of cognitive symptoms. Decreasing medical morbidity by itself can reduce the level of functional impairment in many older people.
Pharmacological strategies for the prevention of dementia are still in Infancy. Although the pathophysiology of Alzheimer's disease is becoming clearer, pharmacological strategies are not available. Statins, although may be beneficial for cardiovascular risk reduction, are not recommended for the prevention of dementia.  Nonpharmacological strategies need to be considered to reduce the risk for cognitive decline.
It is interesting to note that the extent of neuropathological changes often do not correlate with the severity of cognitive impairment in Alzheimer's disease. This lead to the concept of cognitive reserve. Reserve can be described as the ability to tolerate a particular level of brain injury without exhibiting clinical symptoms. Cognitive reserve makes it possible to recruit alternate brain networks or cognitive strategies to resist the effect of the gradually progressing brain pathology. Individuals with a higher cognitive reserve may be able to tolerate the pathological changes of Alzheimer's disease and delay the development of cognitive impairment for longer periods of time. 
According to the previously held hard brain reserve concept, it was thought that individuals differ in their cognitive reserve capacity, depending on certain characteristics of the brains they are born with. This was based on observations that people with a greater head size had a reduced risk of dementia. However, later studies link brain's reserve capacity to its metabolic activity rather than its size.  The brain reserve is now considered to be dynamic and active at the same time, and is modifiable with experience. Cognitive reserve is more of a functional reserve than a structural reserve. Accordingly, individuals with a higher brain reserve perform better on cognitive exercises and possess greater buffer. The cognitive reserve can be enhanced through experience. People with a higher level of education have higher cognitive reserve and the clinical manifestations of dementia would be delayed in them. Engagement in an occupation is also protective, with a more complex occupation being more protective.
Mentally stimulating leisure activities can enhance the cognitive reserve and are protective.  Cognitive reserve is modifiable and it is not determined by early life experiences alone. The brain has a capacity for functional reorganization. This is a powerful compensatory mechanism in late life. Atypical brain networks are activated during successful ageing as well as in early Alzheimer's disease.  Lifespan mental activity may be a significant protective factor. It was shown that hippocampal atrophy was less in individuals with a high level of complex, mental activity across lifespan and this may be one of the reasons for the decreased risk of dementia observed in such individuals during population-based studies.  There are studies which show measurable persisting biochemical changes in the hippocampus following focused memory exercises.  Cognitive exercises in the elderly has been shown to improve the performance in the trained task. Follow-up studies in those individuals have demonstrated a transfer of this effect to general functional outcome which is relevant to the onset of dementia. Moreover, these effects also appear to be persistent over time. , A large, randomized, controlled trial, the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study, demonstrated the effectiveness of targeted cognitive interventions in improving multiple measures of specific cognitive abilities in the elderly, although it did not show generalization of effects to everyday performance.  A longitudinal cohort study reported that the risk for developing Alzheimer's disease is reduced by frequent participation in cognitively stimulating activities.  Participation in cognitive leisure activities like reading, writing, crossword puzzles, board or card games, group discussions, or playing music was associated with reduced risk of dementia as well as mild cognitive impairment (MCI). , Engagement in cognitively stimulating activities may prevent or slow down cognitive decline. Older people should be encouraged to be cognitively active, especially after retirement from regular employment.
Regular physical activity is well-known for its positive health benefits. Unfortunately, sedentary lifestyle is on the increase among all age groups. Most people tend to become less physically active as they grow older. There is evidence for beneficial effects of regular physical activities on cognitive health. Physical exercise can improve cognitive functions in short-term and prevent cognitive decline in long-term. The amount of physical activity may also be important for beneficial effects on cognitive functions.  The protective effect of regular physical activity has been shown to be particularly important in dementia of the Alzheimer's type compared to others. Physically active women seem to benefit more compared to men. 
Aerobic exercises which improve the cardiorespiratory fitness also improve cognitive functions. The improvement would usually be seen on certain cognitive functions like motor functions, cognitive speed, and auditory and visual attention. The reasons for this differential effect are not clear. The improvement in cognitive functions may be mediated through the improvement in cardiovascular functions due to the physical activities.  Studies have also shown beneficial effect of physical activities on executive functions. The relationship between physical activity and executive function, however, is bidirectional. Presence of executive dysfunction often leads to reduced activity level. The participation in physical activities gradually decrease in people with poor executive functions. 
Regular exercise prevents atherosclerotic changes both in the coronary and cerebral circulation, which helps to prevent cognitive decline. Studies have also shown greater hippocampal volume and better cognitive functions in individuals doing regular aerobic exercises. Greater cortical volume was also observed in such individuals. Regular exercise during midlife can reduce the risk of dementia. Physical exercise enhances the release of neurotrophic factors. The levels of neurotrophic factors like the brain-derived neurotrophic factor are found to be reduced in the brains of people with Alzheimer's disease. 
In a study conducted among elderly women, higher levels of physical activity were associated with lesser cognitive decline in all measures of cognition. The cognitive status of elderly women who walked regularly was comparable to women 3 years younger, but were not physically active.  Low physical activity is estimated to be the fourth largest risk factor for noncommunicable diseases.  Participation in leisure activities, thus, can reduce the risk of cognitive decline. Healthy elders who start exercise programs have reduced risk for dementia.  Twenty minutes of vigorous physical activity on 3 or more days or 30 min of moderate activity on 5 or more days per week reduces the risk of dementia.  Promoting exercise in the elderly will have a major public health impact by reducing the burden of dementia through delaying the cognitive decline. It also protects from a number of other noncommunicable diseases.
A healthy diet can help to prevent cognitive decline. Dietary factors like saturated fatty acids, high calories, and alcohol are known to increase the risk of dementia. On the other hand, diets rich in vitamins, antioxidants, and methionine-rich amino acids are considered as protective. Excess intake of calories can lead to obesity, diabetes, and vascular disorders; which in turn would increase the risk of cognitive decline in late life. A diet rich in docosahexaenoic acid (DHA) and omega-3 essential polyunsaturated fatty acid has been shown to be protective. On the contrary, diets containing high quantities of saturated fat, trans fat, and cholesterol is harmful. 
Using vegetables, legumes, fruits, and whole grains as primary staples of diet may protect against dementia. Vitamin E from food sources itself, rather than from supplementation, may help to prevent cognitive decline. Natural sources of vitamin E include seeds, nuts, green leafy vegetables, and whole grains. Vitamin B12 and folic acid is known to have an important role in mental health and cognition. Adequate intake of vitamin B12 from dietary sources, fortified foods, or supplements is essential in preventing cognitive decline. 
Dietary polyphenols are potent antioxidants and are thought to be useful in slowing neurodegenerative processes. Green tea flavonoids have been demonstrated to have neuroprotective functions such as antioxidation, iron chelation, and anti-inflammation. Green tea consumption was shown to be associated with a significant reduction in functional disability in the elderly. 
Dietary spices, especially turmeric also have an important role in the prevention of cognitive decline. Researchers have noted a reduced prevalence of Alzheimer's disease in the elderly in India, and attributed this to the widespread use of turmeric in Indian cuisine. Turmeric contains a natural phenolic antioxidant, curcumin, which is responsible for its neuroprotective properties through its antioxidant and anti-inflammatory effects. Curcumin, thus, may have a role in the prevention and treatment of dementia and other neurodegenerative disorders in the future. ,
The traditional Mediterranean diet (MeDi) is composed of high amounts of vegetables, fruits, legumes, and cereals; high amounts of olive oil; moderate quantity of fish; moderate amounts of dairy products; low amounts of meat and poultry; and moderate amounts of wine generally consumed along with meals. Consumption of MeDi is associated with a multitude of health benefits including reduced risk of cardiovascular disease, cancer, and mortality. Complex phenols and many other substances with antioxidant properties are present in abundance in this diet. Adherence to MeDi was found to be associated with a reduced risk of developing MCI and also a reduced risk of MCI conversion to Alzheimer's disease. , Higher adherence to MeDi was also shown to be associated with a slower decline in the mini-mental state examination (MMSE) scores in the elderly.  Risk factors for late life dementia like midlife obesity, diabetes, and hypertension are influenced by diet. Therefore, MeDi may impart its protective effect on dementia through modification of these vascular risk factors also. 
A relationship between social relationships and health has been noticed long back. Lonely, less socially active individuals have a poorer physical and mental health compared to their socially active counterparts and are more likely to die earlier. The biological process that links social activity and health is yet to be fully understood. 
Social activities also have relationship with the risk of development of dementia. Social, mental, and physical activities can reduce the risk of dementia, probably through their cardiovascular system effects. This may also be influenced by the fact that socially active individuals usually adhere to a healthier lifestyle. Several studies have found that higher level of social activity is protective for dementia and lonely individuals get demented early. ,,, Restrictions of social activity may sometimes be due to prodromal cognitive and depressive symptoms seen during early phases of dementia.
Social networking can occur in different settings like family, work, and friend circles. According to Berkman and colleagues, social networks affect health by operating through five main mechanisms (social support, social influence, social engagement, person-to-person contact, and access to resources and material goods), which influence different health outcomes through three major pathways: behavioral, psychological, and physiological.  It is proposed that social network, mental activity, and physical activity may be acting through some common pathways in the prevention of cognitive decline. 
Multidomain approaches addressing a number of risk factors of dementia are found to be more effective than addressing individual risk factors. Simultaneous change in a number of risk factors even in small magnitudes may be protective. The Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) trial demonstrated the effectiveness, feasibility, and safety of a multidomain approach.  Even small changes in individual risk factors have a large effect on cognition. Significant intervention effects were noted in the overall cognition, executive functioning, and processing speed in this trial. Several dementia prevention trials are now targeting multiple risk factors to prevent cognitive decline.  The initial results seem to be promising.
Dementia is a major public health challenge with diverse consequences. MCI is more common than dementia. Many older adults would experience cognitive symptoms in late life. Prevention of cognitive decline is becoming increasingly important in an ageing world. Cognitive decline beyond a certain level often gets translated into need for care and support. Population-based interventions are needed to delay the onset of cognitive decline and slow down its progression. This can reduce long-term care needs. Encouraging individuals to adhere to a healthy lifestyle and remain physically, socially, and cognitively active throughout the life span seems to be a promising strategy. Multidomain preventive strategies will have a significant role in reducing the global burden of dementia. More research is needed in this area.
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