Physical activity and exercise
Recent evidence indicates substantial benefits of physical activity that extend across physical, cognitive, and emotional domains in later life. Current recommendations from the Center for Disease Control and Prevention (CDC) suggest that individuals 65 years of age and older get 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic activity each week and two or more days of muscle-strengthening activities (
http://www.cdc.gov/physicalactivity/everyone/guidelines/olderadults.html). Physical fitness, including aerobic power, flexibility, and muscle strength, decline with age (
63,
64). Older adults are the most sedentary segment of the population, with 28% to 35% of older adults reporting no leisure-time physical activity (
http://www.ahrq.gov/ppip/activity.htm).
Longitudinal studies indicate a relationship between physical fitness and cognitive ability (
65,
66). Physical fitness appears to provide some level of protection from cognitive impairments, possibly by offsetting age-related structural changes in the brain as people age (
67). In a meta-analysis of 18 physical activity intervention studies with human subjects published between 1966 and 2001, older individuals who were randomized to training interventions that included either aerobic (cardiovascular) training or combination training (cardiovascular and strength) scored higher on measures of executive function, cognitive control, and spatial and processing speed tasks by about a half a standard deviation (
65).
There are a number of theoretical mechanisms for the influence of physical activity on cognitive function. Aerobic fitness is associated with increased expression of brain-derived neurotrophic factor (BDNF) (
68) as well as
N-acetylasparatate (NAA) in the frontal cortex (
69). NAA levels decline with age and are associated with poorer working memory performance; higher levels of aerobic fitness may offset this age-associated decline influencing working memory capacity (
69). In addition, physical exercise may reduce oxidative stress (
70) and increase supplementary growth factors that support angiogenesis, neurogenesis, and synaptic plasticity (
71). In a review of human intervention studies Kramer and Erikson (
72) proposed that physical fitness produces dynamic changes in patterns of event-related brain potentials (ERPs) in older adults, mirroring those of younger adults, particularly increasing P3 amplitude and decreasing P3 latency.
Physical activity may also have antidepressant effects in older adults, as seen in a number of studies (
73,
74) showing that increases in exercise training significantly improves depressive symptoms in older adults (
75). In one study of the National Health and Nutrition Examination Survey (NHANES) 2005–2006, adults ages 20 and older who participated in moderate levels of physical activity, for 30 minutes a day/three or more days a week, were 28% less likely to show signs of depression than individuals who do not participate in any type or low levels of physical activity (
76). Stathopoulou et al. (
77) reported a meta-analysis of 11 physical activity treatment outcomes studies with individuals with depression, a small subset of studies reviewed were conducted with older adults. The authors found that high intensity exercise had greater improvement in treating depression, improving quality of life and sleep quality; aerobic and anaerobic exercise appeared to yield the same gains in all studies reviewed. Interestingly the analysis suggested that exercise-alone showed lower relapse rates than combination (exercise and pharmacotherapy) (
77). The mechanisms of physical activity on emotional health are unclear, but physical activity may mitigate the harmful effects of prolonged stress on cellular, neural, immunologic, and emotional health (
68). Regular physical activity may augment endogenous antioxidant systems, which, in turn, decreases oxidative stress (
78). In addition, research suggests that endogenous opioids (i.e. endorphins, dynorphins), which are increased during and directly following exercise, contain biochemical characteristics that have been associated with mood regulation (
79).
A common question practitioners face is which treatment models best motivate exercise? In a review of 38 randomized controlled trials (RCTs) of physical activity that included a total of 57 interventions, three types of interventions were compared: home-based, group-based, and educational (
80). In home-based physical activity interventions, participants performed their prescribed exercise routine in their home; group-based physical activity interventions included supervised group-based exercise; while educational physical activity interventions included an education piece with information on exercise and health as well as encouragement to participate in physical activity. Results from this review suggested that while home-based and group-based interventions had the best outcomes, sustainability remains a problem (
80).
Technology provides for evolving means of motivating exercise, which may increase access and motivation to exercise. Exergames combine computer-simulated environments and physical activity in the context of pleasant activity. In a pilot study, 12 weeks of exergames participation was associated with significant reductions in subsyndromal depressive symptoms and improvements in health-related quality of life, and cognitive performance (
74). Van Stralen et al. (
81) developed a computerized intervention for physical activity that focused on the environmental issues that are often barriers to physical activity in older adults. Intervention strategies included targeting motivation, premotivation, and postmotivation, as well as environmental issues. Results suggested that targeting environment increased participants’ physical activity by one hour per week.
Nutrition and dietary interventions
The U.S. National Health and Nutrition Examination Study (NHANES), a national level cross-sectional study of 11,145 participants ages 18 years and older conducted between 2007 and 2010, found that older adults ages 60 and older had higher levels of abdominal obesity and hypertension than any of the younger age groups, with the highest levels being in the 80 and older group (
82). Nutrition plays a significant role in prolonged health and health promotion throughout the life course. Owing to relationships identified between nutritional intake and mild cognitive impairment (
83,
84), depression (
85,
86), physical deterioration (
87), and quality of life (
88), promotion of successful aging in older adults should include healthy dietary practices (
89).
In a study of unique nutrition interventions from 1950 to 2008, 15 high quality randomized control trials were found: 10 nutrition education and counseling interventions and five nutrition supplement interventions (
88). Within this review nutrition counseling interventions that incorporated active participation demonstrated the best nutrition-related outcomes. These interventions invited participants to develop personalized health plans, set goals, and develop higher levels of self-efficacy. In an older review of nutrition interventions and education for older adults, 25 studies met the criteria for inclusion (
89). Studies were more successful if they included simple, practical nutrition messages, provided education to increase motivation and nutrition knowledge, offered incentives for attendance and change, and when behavioral interventions produced readiness to change and self actualized goals.
Calorie restriction (CR) or dietary restriction, a 10%–40% reduction in nutritional energy intake, is frequently considered an avenue for extending lifespan and health span (
90,
91). Calorie restriction has been investigated in a number of species, including rodents, rhesus monkeys, and humans (
90,
92). There is some controversy as to how much calorie restriction is necessary and the magnitude of the effect, as Mendelsohn and Larrick (
91) discussed the impact of confounds such physical activity and muscular fatty acid metabolism as influencing variation of in outcomes. The mechanisms of calorie restriction are of course of great interest, in particularly whether it is affecting the rate of aging or postponing age-related disease (
91). Calorie restriction may indeed reduce risk for cardiovascular disease, cancer, and diabetes in humans (
92). For example, in a recent review of studies conducted with various animal models, it appears that calorie restriction is associated with a lower risk of cancer due to a antitumor effect associated with a decrease in anabolic hormones, oxidative markers, inflammatory cytokines (
93).
Dietary patterns also have influence on the likelihood of successful aging. The Mediterranean diet (
87,
94) is characterized by the consumption of plant foods, fresh fruits, olive oil, fish, along with low amounts of red meat, a low to moderate intake of dairy, and wine consumed with meals (
94,
95). The Mediterranean diet has been associated with decreased mortality, a reduction in cardiovascular and chronic diseases, as well as a reduction in cognitive decline, and risk of Alzheimer’s disease (AD) (
95,
96). The Health, Aging, and Body Composition Study (Health ABC) that used a sample of 3,075 older adults aged 70 to 79 indicated that older adults with highest conformance to the Mediterranean diet (
87) evidence less decline in mobility over eight years. In a sample of 1,410 older adults, Feart et al. (
97)found that while adherence to the Mediterranean diet was associated with a slower decline on MMSE scores, it was not significantly related to performance on other cognitive tests. In another study, 1,393 cognitively normal participants were followed until they were diagnosed with mild cognitive impairment (MCI) or until last follow up 4.5 (± 2.7) years (
84). Higher adherence to the Mediterranean diet was associated with a lower risk of MCI; compared with those in the lowest tertile of adherence, participants in the middle tertile of adherence had 17% less risk for MCI and participants the highest tertile had 28% less risk of MCI (
84). It is unclear what the “active ingredients” in the Mediterranean diet, yet suspected ones are Vitamin B12 and folate, antioxidants, monounsaturated fatty acids, and moderate amounts of alcohol (
87,
96,
97).
Vitamin D deficiency (
83) appears to predict decreases in cognitive functioning and the development of Alzheimer’s disease. In a study of 498 older adult women who did not take vitamin D supplements, women who developed Alzheimer’s disease during the following 7 years had the lowest baseline vitamin D intakes compared with those who did not develop dementia (
83). Vitamin D supplementation has been shown to reduce postural sway, increase lower extremity strength gain, and decrease the time it takes to complete the Timed Up and Go test in a review of 13 articles on vitamin D supplementation in older adults (
98). In a large study (N
=81,189) of postmenopausal women ages 50–79, vitamin D supplementation was also associated with a 20% reduced risk of depression from baseline to 3-year follow-up (
99).
Finally, the supplement Resveratrol has also been promoted as a preventive agent for several diseases and potential therapy (
100). While tests on laboratory animals have suggested antiaging, anticarcinogenic, anti-inflammatory, and antioxidant properties associated with Resveratrol, only recently have human clinical trials been conducted showing matched potential to prevent chronic disease and improve health in humans (
100). Further research needs to be conducted to increase knowledge about the totality of benefits of this supplement as well as other supplements whose claims of positive effects are often not subject to empirical study or governmental oversight (
101).
Cognitive interventions
There is, of course marked interest in interventions that might slow the rate of cognitive decline and reduce risk of dementia (
70). There are a variety of approaches that are aimed at enhancing cognitive ability, including traditional classroom-based cognitive training, computerized cognitive training, and cognitive stimulation. In a review of RCTs of cognitive interventions published between August 2007 and February 2012 that involved guided practice of cognitive tasks, cognitive training appeared to be beneficial for numerous facets of objectively measured cognitive functioning, including fluid intelligence, attention, processing speed, executive functioning, and memory performance (
102). For example, the Advanced Cognitive Training in Active and Vital Elderly (ACTIVE) study included 2,168 older adults with good functional and cognitive status randomized across four treatment groups, memory, reasoning, speed of processing, and control (
103). Five years postintervention all three groups retained a significant effect on cognitive outcomes, although, as is typical the effects were restricted to the targeted outcome (e.g., memory training only significantly improved memory) and effects on distal outcomes (e.g., functioning) were weaker than that associated with cognitive abilities. Nonetheless, at 5-year follow up, the participants in the reasoning group had significantly less difficulties with independent activities of daily living.
One question is whether training should target multiple versus single domains. A sample of 270 community-dwelling older adults, 65 to 75 years old, who evidenced high functional capacity and no reported cognitive impairment, were enrolled into one of three treatment groups (multiple domain, single domain, or control group) (
104). Single-domain training centered around reasoning training such as numerical reasoning and verbal reasoning, while multiple-domain training focused on reasoning, visuospatial map reading skill development, memory, problem solving strategies, handcraft making, and health and physical exercise. Both single- and multiple-domain training showed significant training effects on visual reasoning; single-domain training demonstrated significant effects on work interference and visuospatial/constructional score, and multiple-domain training showed effects on immediate and delayed memory. Multiple-domain training was more effective in follow-up analyses, suggesting it may be more advantageous for long-term effects on cognitive decline when compared with single-domain training.
Another question is whether computerized interventions can produce similar effects, which, in light of their portability and ease of administration, could provide for greater reach of interventions. A recent review found that computer-based cognitive interventions showed comparable results to traditional cognitive interventions (
105). Online video games have been described as an intervention for improving cognitive control in older adults (
105). In a study of the impact of video games on cognitive control, 54 older adults were randomized to play strategy games for 30 minutes per day for 7 weeks, while a control group answered test questions about documentaries online each day (
106). Results suggested that using online cognitive training games can increase inhibition and inductive reasoning, while selective attention was significantly increased in the documentary group as measured by the useful field of view test. A recent strategy has been combining cognitive stimulation with physical activity. For example, a clinical trial indicated that exergame cyber cycling for 3 months was associated with greater gains in executive function than participants who spent comparable time exercising on a stationary bike, indicating that there may be an incremental benefit of interactive decision making and virtual reality imagery in exergames (
107). While many questions exist about the optimal approach to cognitive remediation and its combination with other kinds of interventions, recent work has shown substantial promise (
106).
Social interventions
Social isolation or loneliness is an important and prevalent health concern in the growing population of community-dwelling older adults (see Nicholson [
108] or Routasalo et al. [
109]). In a RCT of psychosocial group rehabilitation for older adults ages 75 and older, participants were randomized to one of three groups as an intervention participant or control: therapeutic writing and group psychotherapy, exercise and health related discussions, and art and inspiring activities (see Pitkala [
110] or Routasalo et al., 2008 [
109]). Individuals in the intervention groups met once a week for 3 months, a total of 12 times, for 5 to 6 hours including breaks and lunch. Individuals in the intervention groups showed improved health compared with the individuals in the control groups at the 1-year follow-up, as well as reduced rates of mortality and reduced cost of health services (
110). In addition, intervention group participants showed improved psychological well-being scores, and a larger number had acquired new friends at the 1-year follow up compared with control group participants (
109). While the above investigation shows promising results for group interventions that target social isolation, unfortunately at this time interventions for social isolation are still underdeveloped and not well researched (
108).
Volunteering is another intervention for social isolation that is currently understudied. Volunteering offers extensive benefits to the community, as well as enhanced well being and positive health and psychological outcomes to older volunteers (
111). The Baltimore Experience Corps Trial (BECT) (
112) involves pairing older adults with academically at-risk youth, and found that volunteering in this way, in addition to benefitting younger adults, was associated with better cognitive ability in older adults who volunteered compared with a control group. One of the main premises of this trial is that older adults are more likely to want to volunteer their time when the aim of the experience is to contribute to younger generations and to leave a legacy, versus focusing on personal benefits of volunteering on physical and cognitive health and social activity. In a study of community-dwelling older adults in Australia, individuals who engaged in moderate and high levels of volunteering (1 to 7 hours per week) showed higher levels of life satisfaction and positive effect than nonvolunteers (
112).