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Updates |
RC Barnhart, PT, ScDPT, PCS, is Assistant Professor and Academic Coordinator of Clinical Education, Department of Physical Therapy, East Tennessee State University, Box 70624, Johnson City, TN 37614
B Connolly, PT, EdD, FAPTA, is UTNAA Distinguished Service Professor and Chairperson, Graduate Program in Physical Therapy, University of Tennessee Health Science Center, Memphis, Tenn
Address all correspondence to Dr Barnhart at: barnhart{at}etsu.edu
Submitted November 3, 2006;
Accepted May 29, 2007
 | Abstract |
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| Introduction |
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 TopAbstract Introduction Changes in Body Structure...Exercise and Down SyndromeConclusionReferences |
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Down syndrome (DS) is the most frequent chromosomal cause of DD, occurring in 1 out of every 700 to 1,000 live births.5–7 More than 350,000 people in the United States have been diagnosed with DS.8 The nondisjunctive type of trisomy 21 is present in 93% to 95% of individuals with DS.5,9 Less common causes of DS are translocation, when part of chromosome 21 breaks off and attaches to another chromosome, and mosaicism, where the nondisjunction of chromosome 21 occurs before cell fertilization.5 Translocations are responsible for approximately 3% to 4% of cases of DS, whereas mosaicism occurs in about 1% to 3% of cases.9
Like that for other individuals with DD, the life expectancy for individuals with DS has been increasing from an average of 9 years of age in 1929,9 to 12 years of age in 1949,9 to 35 years of age in 1982,9 to 55 years of age or older currently.5,6,10,11 Therefore, changes in body function and structure secondary to aging have the potential to lead to activity limitations and participation restrictions for individuals with DS. The purpose of this update is to: (1) provide an overview of the common body function and structure changes that occur in adults with DS as they age and (2) apply current research on exercise to the prevention of activity limitations and participation restrictions. The conceptual model guiding the discussion in this update will be the World Health Organization's International Classification of Function, Disability and Health (ICF).12
The ICF provides a common language and framework for the description of health and health-related states, outcomes, and determinants.12,13 The ICF emphasizes health and functioning, rather than disability, and is a tool for measuring functioning in society regardless of the reason for an individual's impairments.12 Thus, the ICF focuses on a person's level of health rather than on disability. The emphasis on an individual's level of health is important because diagnosis alone does not predict service needs, level of care, or functional outcomes.12
The ICF model identifies 3 levels of human functioning.12 Human functioning occurs at the level of body or body part (body function and structure), the execution of a task by a person (activities), and the whole person in a social context (participation). Figure 1 illustrates the ICF model.
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| Changes in Body Structure and Function Associated With Aging in Individuals With DS |
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TopAbstractIntroductionChanges in Body Structure...Exercise and Down SyndromeConclusionReferences |
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Physical Conditions
The physical conditions seen in people with DS include thyroid dysfunction, cardiovascular disorders, obesity, and musculoskeletal disorders.5,16 These physical problems can have a negative effect on the quality of life not only for people with DS but their families as well.9,17,18
Thyroid dysfunction.
Adults with DS are at risk for developing both hyperthyroid and hypothyroid conditions as they age, with hypothyroidism being more common.5–7,19 Studies have shown that 20% (age=6–14 years)17 to 28.1% (age=5 days–10 years)18 of children with DS have thyroid dysfunction on initial thyroid function testing, with the majority of these children demonstrating hypothyroidism.20 By adulthood, approximately 40% of all people with DS will develop hypothyroidism.5,6 Untreated hypothyroidism often can lead to symptoms that mimic a decline in cognitive skills; therefore, individuals may be misdiagnosed as having Alzheimer disease (AD).5,6 Other frequently observed symptoms of hypothyroidism in individuals with DS include decreased energy, decreased motivation, weight gain, constipation, bradycardia, and dry skin.5
Cardiovascular disorders.
Mitral value prolapse is reported to occur in 46% to 57% of adults with DS.6,7 Mitral value prolapse can lead to an increased risk of endocarditis, cerebrovascular accident, more severe mitral value prolapse, and heart failure.5 Mitral value prolapse can occur in adults with DS who have no previous history of cardiac pathology. Therefore, some experts7,21 contend that a second cardiac assessment should be given to all adolescents and young adults with DS, regardless of whether cardiac symptoms are present, especially before dental or surgical procedures. Early signs of mitral value prolapse include fatigue, irritability, weight gain, dyspnea with physical activity, bilateral crackles that do not clear with a cough, and a third heart sound.5 As with hypothyroidism, some symptoms of mitral value prolapse could be confused with symptoms frequently seen in people with AD.
Adults with DS may also have a lower cardiovascular capacity than their peers who are mentally challenged but do not have DS. Pitetti et al22 studied the cardiovascular response to exercise testing in adults with DS and adults with mental retardation without DS. They discovered that individuals with DS had significantly lower (P<.01) mean peak oxygen consumption, minute ventilation, and heart rate during exercise testing. Similar results regarding maximum oxygen consumption in adults with DS also were reported by Pitetti and Boneh.23
The lower cardiovascular capacity in adults with DS may be secondary to a lower lean body muscle mass, lower muscle strength (force-generating capacity), thyroid disorders, hypotonic muscle tone (velocity-dependent resistance to stretch), higher incidences of obesity, or an impaired sympathetic response to exercise.22,24 For example, Eberhard et al25 found impaired sympathetic responses (lower peak heart rate and blood lactate concentrations) to maximal exercise in young adults (15–20 years of age) with DS. The lower cardiovascular capacities reported in adults with DS may lead to participation restrictions specifically related to job performance. Job performance frequently is related to physical fitness levels, and a lower cardiovascular capacity may place these adults at a disadvantage in performing job-related physical activities.22
Obesity.
Men with more than 25% body fat and women with more than 35% body fat are considered obese.26 Adults with DS also have reported high rates of obesity.23,26,27 Some authors28,29 have suggested that adults with DS tend to lead a sedentary lifestyle, which results in increased rates of obesity. In a study of physical inactivity among adults with mental retardation, Draheim et al30 reported that less than 46% of the men and women participated in the recommended amount of physical activity and no adults over 30 years of age reported participation in vigorous physical activity.
However, Fujiura et al19 reported that there were not strong links among body mass index (BMI), diet, and exercise in adults with DS. They discovered a significant link (P= .033) between friendships or access to recreation and BMI.19 They concluded that community interactions have a major effect on health. Their findings are consistent with the theoretical model underlying the ICF that environmental factors can influence participation levels.
Andriolo et al31 and Luke et al32 theorized that a lower resting metabolic rate was a cause of increased rates of obesity in individuals with DS. Because both of those studies involved children with DS, Fernhall et al33 tested this hypothesis by measuring the resting metabolic rate in 22 adults with DS (17–39 years of age) and compared these results with those of 20 age-matched control subjects who were not disabled. When the presence of thyroid disease was controlled, the resting metabolic rate in adults with DS was similar to that in the general population. They concluded that a lower resting metabolic rate found in children with DS may predispose them to obesity as adults.
Musculoskeletal disorders.
Because of premature aging, adults with DS might experience musculoskeletal disorders usually associated with elderly individuals earlier than the general population.5 Juvenile arthritis–like arthropathy develops in approximately 1% to 2% of adolescents with DS.7 Mid-cervical arthritis also has been reported to occur at a higher rate in adults with DS than in the general population.5,6 Possibly as a result of low muscle tone, adults with DS are at increased risk for hip dysplasia with dislocation and foot pronation.5 Hresko et al34 found progressive hip instability after skeletal maturity in individuals with DS, which led to a decrease in ambulation skills. Foot pronation may lead to an increased incidence of pedal arthritis in adults with DS.7
Individuals with DS also appear to be at higher risk for developing osteoporosis than the general population. In a study of individuals with mental retardation who were living in the community, Center et al35 found a significantly lower bone mineral density (BMD) (P=.0008 for women and P=.0006 for men) in these individuals compared with the general population. Down syndrome was discovered to be an independent risk factor for osteoporosis. The relatively young age (mean=35 years) of the individuals in the study is of particular concern.
Other researchers36 also have found that individuals with DS appear to be at risk for developing osteoporosis as they age. Subsequently, long-bone fractures and compression factures of the vertebral bodies are common in this population.18 The increased incidence of osteoporosis among adults with DS may be secondary to several factors, including their short stature, low muscle tone, decreased physical activity, early menopause, and decreased muscle strength.37 In addition, the increased incidence of thyroid disease observed in adults with DS compared with adults in the general population and adults with other forms of mental retardation also may contribute to the increased prevalence of osteoporosis in people with DS.5,17,38
Other frequent conditions.
Several other conditions have been associated with the aging process in DS. Children and young adults with DS have a high prevalence of middle ear infections and conductive hearing loss.39,40 The prevalence of hearing impairment increases with age.40 Conductive hearing loss has been reported to be occurring at rates as high as 70% in adults with DS compared with 8% in adults who are mentally challenged but do not have DS.5,41 Therefore, examinations of hearing should occur every 2 years once adulthood is reached.5
Adults with DS also may be at risk for the development of vision problems. The prevalence of visual impairment in adults with DS who are 65 to 74 years of age is 70% compared with 6.5% of adults of the same age who are not mentally challenged and compared with 17.4% of adults of the same age who are mentally challenged who do not have DS.42 Vision problems include cataracts, blepharitis, keratoconus, and excessive myopia, all of which appear to increase in frequency with increasing age.5–7,41,43 The loss of either hearing or vision can have a detrimental effect on adaptive behavior in adults with DS.44
Skin disorders such as atopic dermatitis, fungal infections of skin and nails, and xerosis are common in adults with DS.7 Finally, sleep apnea is reported to occur in approximately 50% of adults with DS.5 Sleep apnea in adults with DS may lead to depression, paranoia, irritability, or other behavioral changes.6
Neurological or Psychiatric Conditions
The most commonly described neurological or psychiatric condition associated with aging in individuals with DS is AD. Depression also may be seen. Early identification and treatment of AD and depression could reverse the functional decline frequently associated with these disorders.45
Alzheimer disease.
Alzheimer disease continues to be an ongoing area of research in adults with DS.46 Almost all adults with DS over 40 years of age display neuropathology consistent with AD.47 Prevalence rates for AD among adults with DS increase with age, with rates of 10% at 30 to 39 years of age, up to 55% at 50 to 59 years of age, and almost 75% at 60 to 65 years of age.6,47 In addition, women with DS who experience menopause before 46 years of age have an increased risk for and an earlier onset of AD.37
The increased prevalence of AD is theorized to be caused by an over-expression of the gene for amyloid precursor protein due to a triplication of chromosome 21 found in most cases of DS.24 This over-expression leads to an increased accumulation of ß-amyloid, the principal component of senile plaques in the brain.24 Symptoms of AD frequently observed in adults with DS include memory loss, weight loss, decreased skills in activities of daily living leading to increased dependency, personality changes, apathy, late-onset epilepsy, and loss of conversation skills (Fig. 2).7,16,46,48–51 In addition, increased rates of depression and mobility problems appear to develop as AD progresses.49,51 Eighty-four percent of adults with DS who have end-stage AD also develop late-onset epilepsy.51
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| Exercise and Down Syndrome |
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TopAbstractIntroductionChanges in Body Structure...Exercise and Down SyndromeConclusionReferences |
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Osteoporosis
As stated previously, individuals with DS have been shown to have decreased BMD compared with other people with mental retardation and individuals without DD.52 Physical activity has been shown to be related to increased BMD in individuals without DD.53 Could increased physical activity also increase BMD among individuals with DS? Angelopoulou et al52 found a significant relationship (r=.877, P<.01) between quadriceps femoris muscle strength and BMD among men with DS. They concluded that encouraging an active lifestyle and exercise for individuals with DS would help prevent osteoporosis. In their review of literature on the effect of exercise on BMD, however, Turner and Robling54 concluded that exercise has only a minor effect on increasing BMD after skeletal maturity but that exercise can reduce fracture risk by decreasing the number of falls an elderly person may experience by improving balance and postural stability.
In conclusion, exercise to improve BMD in adults with DS may have limited benefits because of their long-standing low BMD as well as additional comorbidities.55 Exercise during skeletal growth has been demonstrated to influence BMD during the adult years.54 Physical therapists, therefore, should emphasize dynamic (active) weight bearing when working with children with DS who are either ambulatory or nonambulatory. Partial body-weight–supported treadmill training may provide a means for dynamic weight bearing to improve BMD for both children who are nonambulatory and adults with DS. Additional research is needed to determine which therapies are best for improving and maintaining BMD in adults with DS.
Cardiovascular Fitness
Compared with their peers who are not mentally retarded, individuals with DS, regardless of their age, have lower cardiovascular fitness levels.28,56,57 This lower level of cardiovascular fitness may be the result of poor eating habits, sedentary lifestyle, lack of opportunity for recreational activities, poor coordination, and poor motivation for physical activity.28,56 In addition, the lack of cardiovascular fitness may be secondary to or caused by the elevated obesity rates observed among adults with mental retardation.30 Poor cardiovascular fitness levels also may contribute to the increased risk for heart disease and stroke in adults with mental retardation.58 In addition, cardiovascular fitness levels decrease with an increase in the level of disability.56 Therefore, involvement in cardiovascular conditioning programs would appear to be important for individuals with mental retardation. However, can the cardiovascular fitness levels of individuals with mental retardation, specifically those with DS, be improved with exercise?
Varela et al59 investigated the effects of an aerobic rowing program on the cardiovascular fitness of young adults with DS. Sixteen men (mean age=21.4 years) with DS were assigned to either an exercise group or a no-exercise (control) group. All participants were tested on treadmill and rowing machines before and after the exercise program. The exercise group was involved in a rowing program using rowing machines for 25 minutes per session, 3 sessions per week, for 16 weeks. The authors found no significant difference between the exercise and control groups in peak oxygen uptake, maximal heart rate, and minute ventilation following the 16-week rowing program. However, they found that the exercise group was able to row and walk for longer distances (P<.05) following involvement in the rowing program, demonstrating improvements in exercise capacity without improvements in cardiovascular fitness.
Tsimaras et al28 investigated the cardiovascular response in young adults (mean age=24.5 years) with DS following a 12-week jog-walk aerobic program. Unlike Varela et al,59 however, Tsimaras et al monitored the participants’ exercise heart rate closely and gave reinforcements (edible, verbal, and visual) to the participants during the exercise program. The authors believed that these changes in the exercise protocol explained why their results were different from the results reported by Varela et al.
Unlike the study by Varela et al,59 participants in the exercise program in the study by Tsimaras et al28 demonstrated significant improvement (P<.05) in all physiological parameters compared with the control group, which did not exercise. As in the study by Varela et al, lower baseline maximal heart rate and baseline peak oxygen uptake were found in individuals with DS compared with individuals without DS. Baynard et al27 hypothesized that the lower maximal heart rate may be due to a reduced sympathetic drive and circulating catecholamines. The lower peak oxygen uptake may be due to increased body fat in individuals with DS.28
In summary, young adults with DS between the ages of 21 and 24 years may show improvements in cardiovascular fitness following a well-designed and closely supervised aerobic exercise program. The improvements shown in peak oxygen uptake following aerobic exercise are particularly important because individuals with DS have a lower baseline peak oxygen uptake compared with individuals without DS. Without intervention, the peak oxygen uptake can be expected to decrease as people with DS age, which could result in their inability to perform activities of daily living and perform light work duties, leading to activity and participation restrictions.28,60 Unfortunately, no studies have investigated the effects of an aerobic exercise program on individuals with DS who are over 30 years of age.
Strength Training
Rimmer et al29 investigated the effects of a strength training program on adults (mean age=38.6 years) with DS. In this study, 30 adults with DS participated in 15 to 20 minutes of strength training, 3 days per week, for 12 weeks. Muscle strength was measured before and after training and compared with that in 22 individuals with DS who did not participate in any strength training during the same time period. The authors found that the individuals who participated in the strength training program demonstrated significant (P<.0001) gains in muscular strength compared with the individuals in the control group. The individuals in the exercise group also demonstrated a significant (P<.01) decrease in body weight following the exercise program.
Tsimaras and Fotiadou61 studied the effects of training on quadriceps femoris and hamstring muscle strength and dynamic balance (balance associated with walking62) in 25 men (mean age=24.5 years) with DS. Fifteen men were assigned to an exercise group, and 10 men were assigned to a control group. All subjects took part in testing of peak torque, isokinetic muscle endurance, and dynamic balance before and after the exercise program. Dynamic balance was measured through the use of a balance deck and determined by a stabilometer in 30-, 45-, and 60-second intervals.
The experimental group was involved in a 12-week exercise program at a frequency of 3 sessions per week for 30 to 35 minutes per session. Each session consisted of a 10-minute warm-up period followed by a 15- to 20-minute training period consisting of dynamic balance activities and plyometric exercises with and without resistance and ended with a 5-minute recovery period. The experimental group demonstrated significant (P<.01) improvements in isokinetic peak torque and isokinetic endurance of the lower extremities following the training program. The control group showed no improvement in peak torque or endurance. The experimental group also showed a significant improvement (30 seconds: P<.01; 45 seconds: P<.001; 60 seconds: P<.01) in dynamic balance.61
The results from both of these studies29,61 are important because many individuals with DS will need to maintain or improve their muscular strength in order to keep working as they grow older. Furthermore, because individuals with DS are at risk for obesity, strength training may provide a means for weight control.
Summary
Exercise programs appear to have the potential to positively affect the overall health of adults with DS, thereby increasing the quality of life and years of healthy life for these individuals. However, there is a need for more research investigating the effects of exercise on adults with DS over 40 years of age. In their meta-analysis of aerobic exercise programs for adults with DS, Andriolo et al31 identified only 2 studies of good quality.
No studies were found investigating the effects that exercise may have on the symptoms of AD in the population with DS. Because exercise has been shown to modify brain function63 and may be related to improved cognitive functioning among adults without DS,64,65 exercise may help decrease the severity of symptoms experienced by adults with DS who also have AD. Additional research investigating the effects of exercise on the symptoms of AD among individuals with DS is needed.
| Conclusion |
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TopAbstractIntroductionChanges in Body Structure...Exercise and Down SyndromeConclusionReferences |
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| Footnotes |
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| References |
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TopAbstractIntroductionChanges in Body Structure...Exercise and Down SyndromeConclusionReferences |
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