Down syndrome (DS) is one of the major causes of mental retardation in this country. One in every 600 individuals born in the United Sates is affected by this chromosomal anomaly. The phenotypic results of DS can vary greatly. The most frequent findings include mental retardation, orthopedic concerns, cardiac anomalies, vision problems, and epilepsy. In addition, individuals with DS are at greater risk for obesity, and have been shown to have decreased cardiorespiratory capabilities, even when congenital cardiac anomalies are not present.
A physician providing preparticipation care for a person with DS is in the position to assess the nature and extent of motor, sensory, musculoskeletal, mental, and emotional disabilities present that will affect the individual's chances of safely and successfully participating in a sporting activity. Some of these deficits, such as visual refractive errors, may require minor and straight forward adjustments. Other findings, such as atlantoaxial (AA) instability, could prove to be life threatening, and require strict limitations on certain physical activities.
This article offers the primary care physician a review of the more common and significant conditions found in persons with DS. One goal of this article is to prepare physician readers to consider these conditions as a part of the preparticipation assessment of persons with DS. As a result of this assessment, the physician will be in a better position to provide an exercise prescription, participate in the selection of appropriate sporting events, and assist in developing a better understanding between the patient, parents, coaches, and teachers of the expected outcomes of sport participation by a person with DS.
Medical Conditions Associated with DS
AA instability is the orthopedic variant in individuals affected by DS that carries the most serious potential concerns in relation to physical activity and sports participation. It has been recommended that persons with DS who have radiographic evidence of AA instability be restricted from participating in sports that entail a high risk of head and neck trauma in order to prevent the occurrence of an acute and catastrophic spinal cord injury [1,2]. Sports in this category include most contact sports such as soccer, football, and basketball, as well gymnastics, diving, and swimming with a diving start.
In addition, individuals with DS who are scheduled to undergo otolaryngologic surgical procedures or general anesthesia are thought to be at similar risk for spinal cord injury to those persons who wish to participate in high-risk sports [3,4]. The upper airway procedures involve marked extension and rotation of the neck, which may create risk to the spinal cord in individuals with AA instability. During general anesthesia, muscle tone in the cervical region is reduced to the point that previously undetected instability of the AA joint may be unmasked.
The precautions regarding head positioning during general anesthesia in individuals with AA instability do have significance in relation to sport participation. Should cardiopulmonary resuscitation be required for a sports participant with known AA instability, similar care should be taken to avoid excessive jaw thrust or head tilt during resuscitation. These precautions, combined with the common head and neck anomalies present in persons with DS (larger tongue, shorter neck length, and decreased mandible motion), can make cardiopulmonary resuscitation more challenging .
Approximately 10% to 40% of all DS patients have been found to exhibit the radiographic findings of an increase in distance between the anterior surface of the odontoid process, and the posterior aspect of the anterior atlas arch [6–8]. This increase in distance signifies an excess of ligamentous laxity of the transverse and alar ligaments of the AA joint . The instability cannot be detected by examination or clinical criteria . Factors that have been found to affect the range of diagnosis of this radiographic disorder include the following :
- The type of radiographic study used (plain films, CT, or MRI)
- The population studied (adult or pediatric)
- The specific measurement used by the radiologist to evaluate the degree of instability (measured distance between the bony surfaces of the AA joint and neural canal width are two of the techniques that have been recommended)
- Whether consideration of bony anomalies of the cervical spine was given in making the diagnosis
Clinical symptoms of AA instability requiring treatment are rare, occurring in 1% to 2% of individuals [11•]. These symptoms include neck pain and tilt, gait abnormalities, hypertonicity of the lower extremities, weakness, and bowel or bladder incontinence. These symptoms, associated with cord compression, generally occur before age 10, are more frequent in girls, and are generally chronic rather than acute.
The correlation of the radiographic diagnosis of AA instability with neurologic abnormalities is not well established. A number of studies have shown that the radiographic and clinical findings are poorly related , or the radiographic cervical spine findings are clinically insignificant [13–16]. As a result of this poor correlation between radiographic findings and clinical findings, there are no evidence-based guidelines in relation to screening and activity restriction for AA instability. There are several reviews that suggest that individuals with DS should not be screened for AA instability, or barred from high-risk sports and activities [8,17].
The absence of strong evidence in favor of radiographic screening for AA in all individuals with DS is confounded by two significant consensus guidelines in regard to this question. The Special Olympics organization has required routine radiographic screening for AA in all athletes with DS since 1983. The American Academy of Pediatrics confirmed this decision in 1984. In 1995, the AAP recommendation was altered, acknowledging the lack of evidence in support of routine radiographic screening for AA instability. However, the panel did not change the existing recommendation for screening. Because of these guidelines and the life-changing, as well as medical-legal, consequences of the rare acute neurospinal injury in individuals with DS, consideration must be given to some type of screening for AA instability until there are new guidelines based on controlled prospective trials.
The decision in regard to if, when, and how to screen for AA instability should be made by the parents or legally designated caregivers of an individual with DS after they have had the opportunity to consider the potential benefits and limits of screening. Important points to include in this discussion are as follows :
- Screening is recommended for those persons with DS who wish to participate in high-risk physical activities (or those who are going to have head and neck surgery, or undergo general anesthesia)
- Screening recommendations include a plain film of the cervical spine, combined with an MRI of the same region
- Individuals with bony anomalies of the AA or the occipitoatlantal junction are at high risk, regardless of MRI findings, and should be referred to a pediatric spine surgeon
- Asymptomatic individuals with a normal atlantodens interval (ADI) on plain films, and a neural canal width (NCW) of > 14 mm are normal; because these radiographic findings have not been found to change over time [16,18,19], repeat radiographic studies are not indicated
- Individuals with an abnormal ADI (> 4.5 mm) or an NCW of < 14 mm would also benefit from consultation with a pediatric spine surgeon
Additional orthopedic findings that may affect sports participation, and that are more frequently found in individuals with DS include patellar-femoral instability, valgus and varus deformities of the halux, pes planus, scoliosis, and general decrease in muscle tone.
These problems are thought to be related to the generally increased ligamentous laxity of individuals with DS. Knowledge of the increased presence of these musculo-skeletal problems may allow a treating physician to provide more directed assessment, treatment, and preventive care to reduce the possibility of a sports related injury or overuse syndrome. Accommodation and treatment of these problems may include a number of approaches, such as guidance on activity selection and limitations, directed physical therapy to build muscle strength for joint stability, and the use of supportive taping and orthotics.
Cardiovascular considerations in DS
Cardiac anomalies are found in 40% to 50% of persons with DS. In addition, individuals with DS with and without cardiac malformations have been found to have lower cardiovascular fitness levels than their peers . These findings, combined with upper airway malformations of the nasal and oral cavities, create cardiac and respiratory challenges for the individual with DS during exercise or sport participation.
The primary care physician and pediatric cardiologist are in a position to provide guidance in sport selection for individuals with DS and cardiac malformations. In those persons who have pulmonary hypertension, right to left shunting, and/or chronic hypoxia, the physician's advice to pursue athletic endeavors or sports that do not require high cardiac outputs and potentially increase the degree of hypoxia, is critical for the safe participation in sport for that individual.
A number of studies have looked at the cardiorespiratory capacity of individuals with DS and found that these individuals have lower cardiovascular fitness levels than their peers without DS, including peers who have forms of mental retardation other than DS [20,21]. These studies show that individuals with DS have a reduced peak VO2 measurements and lower peak heart rates when compared with persons with other forms of mental retardation, and with the general population without mental retardation.
A number of studies have shown that the peak heart rates in individuals with mental retardation are 10% to 30% lower than the general population . It appears that the peak heart rates found in persons with mental retardation, but not DS are 6% to 10% lower than that expected (adjusted for age) in the general population. The peak heart rates during exercise in individuals with DS are about 15% lower than those found in the non-DS population with mental retardation [20,21].
It has been proposed that this finding of lower peak heart rates in individuals with DS may explain the reduced VO2 max capacity when other variables are controlled . It has been suggested that the low peak heart rates found in individuals with DS may be due to decreased sympathetic activity in these persons . In addition, this decrease in sympathetic response has been proposed as a mechanism that causes a decreased cardiovascular response to training in individuals with DS .
There are conflicting data and discussion in the literature concerning the response to training in individuals with DS. Some have suggested that the physiologic limitations found in individuals with DS, including lower peak VO2 and peak heart rate, limit these persons' abilities to improve their cardiovascular fitness. A systematic literature review  suggests that there is evidence that individuals with DS can improve their cardiovascular fitness through exercise programs. The current American College of Sports Medicine (ACSM) guidelines recommend cardiovascular training programs for individuals with DS. There are currently no randomized controlled trials available that specifically resolve this issue of whether individuals with DS can improve cardiovascular fitness through training.
The issue of whether individuals with DS can improve their maximal cardiovascular fitness may, in the end, not be particularly important. Individuals with DS are prone to being more sedentary, increasing their risks for obesity, osteoporosis, diabetes, and cardiovascular diseases. These problems can in turn affect their ability to perform activities of daily living, work, maintain social interactions, and participate in recreation . If physical activity simply decreases the risks associated with a sedentary lifestyle, with or without an improvement in cardiovascular fitness, the ACSM guidelines for exercise for individuals with DS appear to be warranted. Future studies to measure the effects of physical activity programs in reducing the secondary risks of inactivity would be helpful in supporting the current recommendations.
The Role of the Physician in Supporting Sports Participation for Persons with DS
There is a need for more involvement by qualified health professionals in sports activities such as the Special Olympics . Many athletes with DS are cleared for participation by a personal physician who is not specifically trained to care for an athlete with the disorders associated with this diagnosis.
Birrer [11•] has written an excellent summary regarding the role of the physician in caring for the Special Olympic athlete. These recommendations are directed toward athletes with all types of mental retardation, but certainly apply specifically to DS as well. Physicians interested in caring for athletes with DS are in a position to assess the nature and extent of the mental, emotional, and neurologic impairments of an individual athlete. Ideally, this physician can understand the affects of concurrent health conditions and medical treatments that may affect the athlete's strength, endurance, and coordination. The physician caring for the DS athlete is in the position to facilitate communication and generate understanding between parents, coaches, trainers and other care givers in regard to medical considerations related to sport participation.
A physician caring for athletes with DS will benefit from acquiring additional training and experience in exercise physiology, exercise prescription, and directing rehabilitation (occupational and physical therapy) for disabled children. Knowledge and understanding of specific the affected individual's susceptibilities to environmental conditions and needs for specific equipment are also important. The latter includes specific life support concerns (such as AA instability) to be acknowledged when providing emergency care, or orthopedic concerns when providing sports-related injury care.
Finally, through familiarity with the individual athlete and his or her family, the physician caring for the athlete with DS is in a unique position to empower the athlete to make independent decisions regarding sports participation. In doing so, the physician can assist in developing accommodating the expectations of the sports experience that are held by the athlete, parents, and trainers or coaches.
Individuals with DS will be encouraged to participate in physical activity and sports by family members, teachers, and other care givers. This genetic disorder is frequently associated with orthopedic and cardiovascular findings that can affect exercise tolerance and the personal safety during physical activities. The physician caring for individuals with DS who are planning to participate in sports must be able to screen the athlete for these findings, and direct the athlete's activities in a manner that insures safety, as well as reasonable expectations for the athlete.
Despite the orthopedic and cardiovascular concerns related to sport participation, the increased risks of medical complications due to a sedentary lifestyle make physical activity prescription an essential part of the medical care of the individual with DS.
Ms. Kristin Christensen of the University of Utah Family Medicine residency program staff assisted in the preparation of this article.
References and Recommended Reading
Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance
1. American Academy of Pediatrics: Atlantoaxial instability in Down Syndrome. Pediatrics
2. American Academy of Pediatrics: Atlantoaxial instability in Down syndrome: subject review.Pediatrics
3. Harley EH, Collins MD: Neurologic sequelae secondary to atlantoaxial instability in Down syndrome.Arch Otolaryngol Head Neck Surg
4. Mitchell v, Howard R, Facer E: Down's syndrome and anaesthesia.Paediatr Anaesth
5. Platt LS: Medical and orthopaedic conditions in Special Olympics athletes.J Athl Train
6. Davidson RG: Atlantoaxial instability in individuals with Down syndrome: a fresh look at the evidence.Pediatrics
7. Cope R, Olson S: Abnormalities of the cervical spine in Down syndrome: diagnosis, risks, and review of the literature with particular reference to the Special Olympics.South Med J
8. Cremers MJG, Bol E, de Roos F, van Gijn J: Risk of sports activities in children with Down syndrome and atlantoaxial instability.Lancet
9. Brockmeyer D: Down syndrome and craniovertebral instability.Pediatr Neurosurg
10. Cremers MJG, Beyer JHM: No relation between general laxity and atlantoaxial instability in children with Down syndrome.J Ped Orthop
11.• Birrer RB: The Special Olympics athlete: evaluation and clearance for participation.Clin Pedatr (Phila)
An excellent summary on the role of the physician caring for the Special Olympic athlete.
12. Roy M, Baxter M, Roy A: Atlantoaxial instability in Down syndrome'guidelines and detection.J R Soc Med
13. Selby KA, Newton RW, Gupta S, et al.
: Clinical predictors and radiological reliability in atlantoaxial subluxation in Down's syndrome.Arch Dis Child
14. Pueschel SM, Moon AC, Scola FH: Computerized tomography in persons with Down syndrome and atlantoaxial instability.Spine
15. White KS, Ball WS, Prenger EC, et al.
: Evaluation of the craniocervical junction in Down syndrome: correlation measurements obtained with radiography and MR imaging.Radiology
16. Ferguson RL, Putney ME, Allen BL Jr: Comparison of neurologic deficits with atlanto-dens intervals in patients with Down syndrome.J Spinal Disord
17. Smith DS: Health care management of adults with Down syndrome.Am Fam Phys
18. Pueschel SM, Scola FH, Pezzullo JC: A longitudinal study of atlanto-dens relationships in asymptomatic individuals with Down syndrome.Pediatrics
19. Morton RE, Khan MA, Murray-Leslie C, et al.
: Atlantoaxial instability in Down's syndrome: a five year follow up study.Arch Dis Child
20. Fernhall BO, Pitetti KH, Rimmer JH, et al.
: Cardiorespiratory capacity of individuals with mental retardation including Down syndrome.Med Sci Sports Exerc
21. Pittetti KH, Clinstein M, Campbell KD, et al.
: The cardiovascular capacities of adults with Down syndrome: a comparative study.Med Sci Sports Exerc.
22. Eberhard Y, Etarradossi J, Thermenarias A: Biochemical changes and catecholamine responses in Down's syndrome adolescents in relation to incremental maximal exercise.J Ment Defic
23. Millar AL, Fernhall B, Burkett LN, et al.
: Effects of aerobic training in adolescents with Down syndrome.Med Sci Sports Exerc.
24. Dodd KJ, Shields N: A systematic review of the outcomes of cardiovascular exercise programs for people with Down syndrome.Arch Phys Med Rehabil
25. Fernhall B: Physical fitness and exercise training of individuals with mental retardation.Med Sci Sports Exerc
26. Maxwell BM: The nursing role in the Special Olympic program.J School Health