Pain, Exercise, and Dementia

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To date, very few studies have systematically explored the triumvirate relationship between pain, dementia, and physical activity. Yet the evidence base shows that physical activity for the cognitively intact improves pain outcomes and is protective of cognitive functioning [32, 56, 74, 84]. Evidence is still limited but encouraging that physical activity is also important in supporting the cognitive ability of older adults with neurocognitive disorders [26]. In light of this, is there a dual benefit for promoting physical activity for individuals with cognitive impairment to improve both pain and cognition? Exercise is recommended for older people in general for its positive effects and will be discussed in the section on the relationship between pain and exercise, but a dual benefit would emphasize the added importance of exercise programs for those in pain and with cognitive deficits.

Promoting physical activity in people with cognitive impairment is not without difficulties. For example, older people with dementia have shown decreased levels of physical activity [80], especially those living with dementia in long-term care who are less engaged in physical activity than their peers without dementia [59]. Despite the decreased levels of physical activity in this cohort, studies highlight the benefits of physical exercise for people with dementia, including improvements in gait [71] and physical functioning [64]. The section on physical activity interventions for cognitive function will review the efficacy of activity programs and discuss some of the practical considerations when attempting to utilize these approaches in older people with cognitive impairments.

THE ROLE OF EXERCISE IN THE MANAGEMENT OF PAIN

Introduction

Chronic pain is a complex and challenging condition to treat, heterogeneous in its clinical presentation, and frequently comorbid with other exacerbating health problems. Chronic pain impacts the individual on multiple domains and is associated with emotional distress, disturbed mental state, sleep disturbance, cognitive impairment, movement dysfunction, social and occupational disability, impaired sexual function, financial impact, and overall diminished quality of life [5, 10, 25, 47, 51, 57, 67]. Multifactorial pain models that can address multiple dimensions of the pain experience are needed for comprehensive pain management, though the evidence of the effectiveness of such models on pain and pain-related disability is modest [83]. Nonetheless, these models have value as they target biological, psychological, and sociological components that are fundamentally involved in the development and prolongment of chronic pain.

Treatment for chronic pain includes both pharmacological and nonpharmacological approaches, with physical activity and exercise viewed as particularly important nonpharmacological therapies in any pain management framework. In this context, physical activity is a broad term for any muscle-related body movement that expends energy, whereas exercise is a form of structured physical activity aimed to improve or maintain physical fitness. Many barriers impede optimal utilization of physical therapies for chronic pain patients, with pain itself commonly cited as a principle reason for activity limitation. Still the benefits of physical therapies are clear, though the comparative benefits of specific forms of physical therapies remains equivocal, as does the effectiveness of such treatments in specific subgroups such as people with dementia and pain.

This section reviews the benefits of physical activity therapies for chronic pain management as well as associated barriers in older populations. These therapies will be discussed as they relate to conceptual pain models that are multifactorial in approach and that aim to address the physical, emotional, cognitive, and social components of chronic pain.

Multifactorial Chronic Pain Frameworks

Traditional biomedical models of pain are incomplete in their understanding and management of chronic pain, as these frameworks are often insufficient in either explaining patient pain-related problems, or accounting for the absence of pain in people with similar structural abnormalities as pain sufferers. More contemporary models are multidimensional and have expanded to include psychological and sociological components of pain, recognizing the role of central nervous system processes that may exacerbate and prolong pain and pain-related disability [54]. Within these models, psychological/behavioral factors have seen particular attention as contributors that promote chronic pain, with some emphasis on the concept of fear avoidance [76, 77].

Fear-avoidance models propose that pain may persist due to a patient adopting avoidant behaviors that are a consequence of an excessive fear of pain or injury. Though some of the basic tenets of these models have empirical support [46], recent evidence fails to support some aspects of the model [82], coupled with poorer-than-expected results from clinical interventions based on fear-avoidance principles [63]. Furthermore not all patients can be attributed to fear-avoidance behaviors, as some patients are better characterized as adopting avoidance-endurance behaviors that are considered contradictory to fear avoidance [31]. Finally, these behavioral models also do not address all dimensions of pain, for example, the sociological or environmental factors that contribute to pain and disability.

A unified biopsychosocial model for chronic pain is still needed, especially regarding the rehabilitation around social and environmental contributors to pain. Here, the International Classification of Functioning, Disability, and Health Framework (ICF) [81] can have utility in providing an expanded framework that recognizes the role of social factors and environment in the interaction between functioning and disability. A benefit of such a model in the context of chronic pain is the recognition of the importance of reframing treatment goals for older patients and those with dementia. Whereas goals may be centered on functional restoration and resumption of all physical activities for a younger patient, these goals may not be foremost considerations for older people or those with cognitive impairment. Appropriate goals may instead focus on sufficient improvement for increasing recreational pastimes, social interactions, or functional independence.

Barriers to Physical Therapies for Chronic Pain

Physical activity is a nonpharmacological treatment recommended in chronic pain management guidelines [1, 50]. However, pain itself is recognized as a substantial barrier in physical activity and exercise adherence [61]. This is particularly so with higher levels of pain that severely limits behaviors that typically promote increased physical activity. A further hindrance is that painful conditions often limit the ability for physical movement, and therefore, regardless of the etiology, a consequence of chronic pain is typically a generalized psychomotor slowing of movement with accompanying “stiffness.” These sequelae are generally fatiguing as they are physiologically inefficient [62]. For example, Lee et al. [45] compared patients with and without lower back pain and reported that pain patients had poorer walking performance despite similar exertion levels. Therefore, the pain itself and the associated stiffness and fatigue are all identified barriers to exercise [61].

Other factors such as psychopathology can also impair physical performance. Depression, a common comorbidity of chronic pain, has been shown to compound on poor physical performance, with depressed chronic pain patients showing severely compromised movement speeds [72]. As lower physical activity levels are associated with higher depression levels [9], this suggests a reciprocal detrimental relationship between chronic pain, physical activity, and depression. So in response to barriers such as pain, stiffness, and fatigue, chronic pain patients decrease physical activity, in turn increasing the likelihood of depressive symptomatology, and thereby reinforcing poor physical performance. However, this picture is incomplete as research on survivors of breast cancer with pain suggests that physical activity is only a partial mediator, and that other pathways also explain the relationship between pain and depression [69].

Exercise and Pain

Despite these barriers, two streams of evidence emphasize the importance of exercise for pain management. The first are the limited experimental pain perception studies that suggest that exercise regimes can modify the sensory aspects of pain perception and tolerance. The other line of evidence is clinical outcome studies showing that exercise interventions can improve pain report and pain-related function. Together the evidence highlights the beneficial role of exercise on pain-related outcomes.

Exercise and Pain Perception

Some limited evidence suggests that different exercise modalities can have an analgesic effect on pain threshold and pain intensity. A review of two exercise types (acute isometric exercise for strength training and aerobic exercise for cardiovascular) in chronic pain patients suggests variable results [56], somewhat dependent on the chronic pain condition. For aerobic exercise, the induced analgesic effect size on pain threshold is small at 0.19 (SD = 0.52). Aerobic effect on pain intensity shows more moderate analgesic effects with d = 0.42 (SD = 1.53), but variability is high across studies. Isometric exercise results were mixed and may be dependent on the specific chronic pain condition. For example, there was increased pain perception in fibromyalgia patients while reduced pain perception for patients with shoulder myalgia. In conclusion, literature on the benefits of exercise on pain perception is small and still inconclusive, as compared to the much larger body of work on the benefits of exercise intervention programs on pain relief and other pain-related outcomes.

Exercise and Pain-Related Outcomes

An umbrella review of nine systematic reviews of exercise on fibromyalgia supports the conclusion that exercise training in multiple modalities can improve pain relief and physical function, typically showing small to moderate effects on both domains [11]. The majority of studies included in the reviews were exercise regimes performed two or three times per week, of moderate intensity (64–76% HR max), between 31 and 60 minutes in duration, and over a period of between 7 and 12 weeks. A review of just resistance training for fibromyalgia (exercise training performed against resistance, e.g., hand weights) showed that resistance exercise improves function, pain, muscle strength, and tenderness compared with controls [15]. However, evidence is mixed whether resistance training performs better or worse than other exercise regimens such as aerobics or flexibility exercise.

A review of aquatic exercise training for fibromyalgia also showed some modest improvements of aquatic exercise compared with controls on outcomes that included pain, stiffness, fatigue, function, and muscle strength [12]. However, only two outcomes were clinically significant with aquatic exercise improving stiffness by 27% and muscle strength by 37%. A comparison of aquatic- versus land-based exercise programs showed no significant differences on function, pain, or stiffness outcomes.

A separate systematic review and meta-analysis showed that exercise programs (strengthening, flexibility, or aerobics) for lower limb osteoarthritis were more beneficial for pain relief and improving functional limitations than no exercise [74]. Most of the studies in the analysis are related to knee osteoarthritis. A study that evaluated an integrated rehabilitation program combining self-management, coping and individually tailored exercise regime over 12 supervised sessions for 6 weeks has also shown longer-term benefits persist at 6 months with standardized effect sizes of 0.29 for function and 0.27 for pain, in favor of the rehabilitation group versus usual care [36].

Targeted exercise approaches are also shown to be effective with a systematic review on the effect of exercise therapy (exercise with varying levels of therapist supervision) on chronic low back pain showing modest pain score improvements with exercise therapy compared with low-intensity home exercise without supervision [32]. Eight of 11 studies reviewed showed no difference between exercise therapy and other forms of nonpharmacological treatment modalities. Routine exercise is also shown to improve pain outcomes in peripheral neuropathies. Animal studies (primarily on diabetic neuropathic pain) suggest that aerobic exercise improves degenerate peripheral nerve function [48] and can delay the onset of diabetic pain [17].

In conclusion, there is consensus that for chronic pain patients any type of exercise is better than none [56, 74], and that activity improves quality of life, promotes well-being, and reduces disability [40]. Therapy for chronic pain typically focuses on improving function and activity despite ongoing pain [3], and suggests that core beliefs may need to be challenged (such as fear-avoidance behaviors to exercise and activity) as well as motivational aspects that may be related to fatigue and depression. A study of exercise paired with a cognitive behavior treatment approach suggests that chronic painful osteoarthritis of the knee is amenable to such an integrated treatment approach [36]. Both pain and physical function improved after treatment, and persisted long term [35]. A review of multidisciplinary treatments that included physical exercise with at least one other biopsychosocial treatment approach showed moderate effectiveness of multidisciplinary treatment for reducing pain intensity in the short term, compared either to no treatment/waiting list controls, or other active nonpharmacological treatments [75]. However, the effect was extinguished by follow-up.

Targeting factors that contribute to pain is a foremost consideration. For example, a meta-analysis review of the effect of exercise on depression has shown that exercise has a moderate effect on depression compared with no treatment or control interventions [21], equivalent to a difference of about 5 points on the Beck Depression Inventory [20]. Likewise, another meta-analysis on the effect of exercise on general mood and well-being showed that acute aerobic exercise was associated with increased positive affect [68]. How these results translate to the effectiveness of exercise for chronic pain in people with dementia is still largely unknown. However, a meta-analysis of the general benefits of exercise programs for people with dementia showed evidence of improvements in depression [26]. Movement speed can be improved without increasing pain scores, by using sensory enhancement such as music and virtual reality [66]. Another study suggests that tailored physical activity pacing is more effective than general activity pacing in reducing fatigue [53] and stiffness [70] in osteoarthritis of the knee or hip.

Considerations of Physical Activity Treatment

Caution is needed with the clinical application of physical activity as although exercise is health promoting, its overuse may be harmful and pain promoting [30]. Evidence is also emerging that physical activity levels that are too high are linked with lower back pain [2], suggesting a U-shaped relationship between physical activity and pain with too-low or too-high activity both detrimental to pain outcomes. In comparison, moderate levels of activity are associated with less pain [29, 33]. Determining what constitutes an appropriate level of physical activity can be difficult, though identifying patients as fear avoidance or pain persistent using avoidance-endurance models of pain may be insightful in recommending either increased activity levels or appropriate pacing strategies, respectively [31].

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