In summary, there is emerging research indicating that a Mediterranean diet may provide some beneficial effects on HR-QoL and well-being in healthy older adults compared to a Western-style dietary pattern. There are also a number of studies which also suggest that certain nutrients including omega-3 fatty acids and a reduction in saturated and trans fats may provide some beneficial effects on HR-QoL and other related concepts which impact on HR-QoL such as depressive symptoms and chronic disease, however the role of other vitamins such as vitamin D, A, C and E remain unclear. Further, there are limited studies which have investigated the effect of other nutrients including zinc and protein on HR-QoL and related concepts, with emerging evidence suggesting that there may be a role for lean red meat in reducing declines in HR-QoL related outcomes, although this requires further study. 5.6 Role of exercise in HR-QoL and related concepts
A reduced ability to be physically active and subsequent decreases in muscle strength and endurance have all been shown to influence HR-QoL, which may be due in part to a loss of independence (444). Therefore maintaining physical function and muscle strength through physical activity and exercise may be beneficial for maintaining HR-QoL and well-being, particularly in older adults. While there is some evidence from cross-sectional and prospective studies and RCTs indicating that regular physical activity and exercise training can improve overall QoL and many of its subdomains in older adults, questions still remain with regard to what type and dose
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of physical activity or exercise training might be optimal and whether these beneficial effects occur in healthy and at risk groups (e.g. those with chronic disease). The following section will provide an overview of the effect of general physical activity and exercise on HR-QoL and related concepts such as depression, as well as the specific effects of aerobic exercise and PRT, in older adults.
As indicated above, there is some evidence which suggests that there is a beneficial effect of general exercise and physical activity on QoL and depression in older adults. One 5-year follow-up study of 174 older adults with a mean age of 67 years who completed a six-month exercise RCT (randomised to receive either moderate- intensity walking three times a week or stretching-toning program three times a week [control]) found that habitual physical activity levels at one year of follow-up was associated with improved psychological constructs including self-efficacy, self- esteem and positive affect which were in turn, associated with greater QoL (as measured by the Satisfaction With Life Scale) (445). Further, changes in physical activity were found to be associated with increases in physical self-esteem and positive affect (mood) with the latter having a direct influence on improvements in QoL in this study (445). The benefits to affect and self-esteem were thought to be related to the social cognitive theory which suggests that increases in self-efficacy may mediate the relationship between physical activity and QoL (445). Similarly, a meta-analysis of 56 RCTs conducted in healthy and clinical populations (rehabilitation or disease management) including those with musculoskeletal, neurological and pulmonary conditions as well as cancer, CVD, rheumatoid arthritis, renal disease and fibromyalgia, found that exercise interventions overall had a positive effect on overall QoL three to six months following an intervention in rehabilitation patients but not in healthy or disease management groups (446). Despite the lack of an overall improvement in QoL in healthy populations, it was found that physical and psychological domains of QoL did improve in this group (446). With regard to the training dose, light-intensity (not defined) exercise conducted in group settings improved QoL overall, although improvements in physical aspects of QoL were reported following moderate-intensity exercise (446). The benefits for QoL following light-intensity but not moderate-intensity exercise were thought to be potentially due to the presumably low fitness level of participants as aerobic fitness has previously been found to effect a person’s enjoyment of higher intensity exercise (446). Overall, it appears that while changes in habitual physical
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activity may be related to QoL in healthy older adults, the effect of exercise may be greatest for clinical populations.
There is also some evidence to suggest that physical activity and exercise may also be beneficial for depression, which is related to HR-QoL. One review of 67 observational studies and RCTs investigating the effect of physical activity on depression in adults aged 17 years and over found that both short (<1 hour per week) and long duration (up to 554 minutes per day) physical activity was associated with a reduced likelihood of depression with vigorous intensities being more strongly associated than lower intensities (447). Further, exercise has been found to decrease depressive symptoms and increase HR-QoL in individuals with AD (448), suggesting that exercise may also be beneficial for improving certain components of HR-QoL in those who are cognitively impaired. However, a potential limitation to these findings is that it has previously been suggested that there is no optimal dosage of exercise which is beneficial for depressive symptoms as beneficial effects have been found at multiple intensities and doses (447), although this has not been thoroughly investigated.
There have also been a number of studies which have investigated the effects of different modalities of exercise such as aerobic training and PRT on HR-QoL. With regard to aerobic exercise, the available data indicates that aerobic exercise is beneficial for improving both HR-QoL and depression (23, 30, 449). For instance, one review reported that moderate-intensity aerobic exercise (such as walking, aerobics or aerobic training) was beneficial for improving behavioural, affective and mood aspects of HR-QoL, although there was also some evidence for a positive affect following low intensity, high intensity and self-selected intensities of aerobic exercise (30). Further, one RCT conducted in 46 sedentary men aged between 60 and 75 years found a decrease in depression and anxiety ratings in those participating in an aerobic exercise program on three days a week for six months, compared to those who were sedentary (mean decrease of 5.74 and 0.69 respectively for Geriatric depression scale [GDS] scores and 12.22 and 2.87 for trait anxiety as measured by Spielberger State -Trait Anxiety Inventory [STAI]) (449). Further, improvements in all domains of the SF-36 (a measure of HR-QoL) was found for the exercise group compared to the control group (449). In line with these findings, a review of the effects of exercise on brain health found that aerobic exercise can be as effective as
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pharmacological anti-depressants as a treatment for depression (23). In contrast, a meta-analyses of 14 RCTs found that there was no difference between aerobic and non-aerobic exercise (such as PRT) modalities for reducing depression, although it was noted that further research was warranted due to a lack of RCTs in clinical populations with adequate follow up (450). This suggests that other types of exercise such as PRT may be equally beneficial for improving HR-QoL and depression. In support of this, an 8-month RCT conducted in 50 healthy older adults aged over 60 years found that those randomised to an aerobic training (70-80% of maximal heart rate) or resistance training (80% of 1-RM) group which trained on three days per week, improved their physical component scores compared to the controls (451). While the improvements in the physical component score were more marked in the resistance training compared to the aerobic training group (10.0 ± 15.3 versus 2.1 ± 12.2 respectively), improvements for the general health score were similar in both groups (16.8 ± 17.0 versus 14.4 ± 19.7 for resistance and aerobic training respectively). In contrast, the improvements in the mental health score were greater in the aerobic group (2.9 ± 27.0 versus 21.9 ± 37.3 for resistance and aerobic training respectively) (451). This suggests that although either aerobic or PRT can induce similar improvements in overall HR-QoL independently, they may do this by influencing different aspects of HR-QoL. This suggests that the type of exercise may be important when designing an intervention to target specific aspects of HR-QoL, and it indicates that multi-component exercise may have added benefits for HR-QoL overall compared to single modalities.
Research suggests that PRT can increase neural recruitment and activation of muscles, which may contribute to improvements in physical functional outcomes (452) which may subsequently improve HR-QoL. The findings of one recent study support the notion of maintaining muscle for HR-QoL, reporting poorer nutritional status, cognitive function, HR-QoL and increased depression in hospitalised older adults with low muscle strength (handgrip strength less than 30 kg and 20 kg in men and women respectively) compared to those with normal muscle strength, over a six month period (453). In addition to this, one 12-week intervention study conducted in 49 healthy older men aged 60-81 years found improvements in the role physical, general health and physical component summary score following strength training three times a week, despite baseline scores being above the population average (454). Similar results were reported in another study which examined the long term effects
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of a 12-week twice-weekly PRT program (60% of 1-RM) on HR-QoL in 135 older adults aged 65 years and over. In this study, they found that physical functioning, role physical and mental health domains (as measured by the SF-36) improved significantly in the training group post-intervention and one year following the intervention (role physical and physical functioning only), when training was maintained (455). In the de-training group (training not continued post-intervention), scores for vitality and mental health domains as well as physical functioning and general health, decreased one year post-intervention (455). However, no domain scores were lower one year post-intervention than at baseline (455), indicating that positive effects of exercise on HR-QoL can be sustained even if training is not continued. This highlights the importance of maintaining training to ensure that HR- QoL is also maintained. The declines in the mental health domains was suggested to be due to a potential decline in positive feelings relating to the social interaction provided through the group training sessions, which may have influenced HR-QoL ratings (455). This is supported by the findings of another 12-week RCT conducted in 119 adults aged 65 years and over, which found that only the mental health domain (as measured by the SF-36) was improved in the twice-weekly PRT group (60% of 1-RM) when compared to the control group (354).
With regard to the dose of PRT, one review which included studies that examined the acute effects of low or high-intensity PRT reported that these studies have obtained divergent results on HR-QoL, which may be due to differences in the length of time between post-exercise and assessment of HR-QoL in acute studies (30). For example, acute studies which assess HR-QoL immediately following exercise (within a couple of hours) may capture the effects of fatigue related to the exercise which may result in lower HR-QoL scores, compared to studies which assess HR-QoL after the participants have had time to recover from the immediate sessions (e.g. one week following exercise). This review however, did not acknowledge studies which have investigated the long term effects of PRT on HR-QoL. Another review found that lower exercise intensities in general were associated with greater enjoyment and persistence whereas moderate intensities were preferred and associated with positive psychological responses in fitter adults (446). In clinical populations however, lower intensities were associated with benefits for HR-QoL compared to higher intensities (446). A limitation of this review however, was that the exercise types were all grouped together and could not be analysed separately due to the small number of
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studies in each group (446). Thus, it cannot be determined whether certain intensities for particular types of exercise are more beneficial than others for HR-QoL. Further research into the long and short-term effects of PRT on HR-QoL, are needed.
Taken together, the findings above suggest that aerobic and PRT may independently have beneficial effects on HR-QoL in older adults, but may act on different aspects of HR-QoL. On this basis, it is likely that the combination of aerobic and resistance training would be most beneficial to improving multiple measures of HR-QoL. However, currently the research into the effects of a multi-component exercise program on HR-QoL is unclear. A recent meta-analysis of 36 RCTs investigating the effects of physical activity and psychological well-being in older adults found that the combination of aerobic and resistance exercise had the smallest effect size compared to each type of exercise alone for psychological well-being (31). However, it was noted that a limitation of at least half of the studies included in the meta- analysis was that they used life satisfaction as a measure of HR-QoL rather than more specific outcome measures (31) such as the Assessment of QoL instrument (AQoL) or the perceived well-being scale (PWB) (415). Despite this, a systematic review of 15 RCTs which included multi-component exercise comprising aerobic, strength and balance training in older adults found that generally, there was no improvement in functional or HR-QoL outcomes (456). However, it was noted that seven of the studies incorporated a home-based intervention (456), which may have impacted on execution and intensity of the exercise and any potential social interaction, thereby potentially limiting the effects of the training on HR-QoL. Further research investigating the effects of a multi-component exercise program, namely aerobic combined with resistance training, is required before conclusions about the benefits on HR-QoL can be drawn.
5.7 Effects of multi-component exercise in combination with protein on HR-QoL