Course:KIN366/ConceptLibrary/DownSyndrome

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Movement Experiences for Children
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KIN 366
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Instructor: Shannon S.D. Bredin
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Down syndrome is a genetic congenital (present from birth) disorder caused by a chromosomal defect causing physical abnormalities, intellectual impairment and developmental delays (Bull, 2011). Down syndrome is seen across all cultures, and is found in all parts of the world. It is not bound to a certain race, social class or time period (Gunn, 1993) and it is currently the most common genetic condition of live-born infants in Canada (Templeton & Wilson, 2006).


Origin

For centuries, people with Down syndrome have been alluded to in art, literature and science (National Down Syndrome Society, 1979). However, it wasn’t until the late nineteenth century when it was first described academically by John L. Down (1828 – 96). John was an English physician who first characterized the condition as a distinct separate entity and was later recognized as the “father” of the syndrome (NDSS, 1979). In recent history, advances in science and medicine have enabled further research to investigate the characteristics of people with Down syndrome (NDSS, 1979). In 1959, the French physician Jérôme Lejeune identified Down syndrome as a chromosomal condition and most recently in the year 2000, an international team of scientists successfully identified and catalogued each of the approximately 329 genes on chromosome 21 (NDSS, 1979), allowing for a deeper understanding of the disorder.

Prevalence

It is estimated that the incidence of Down syndrome is between 1 in 1,000 to 1 in 1,100 live births worldwide. This means that each year around the world, approximately 3,000 to 5,000 children are born with Down syndrome (World Health Organization, 2015).

Types & Cause

Typically a human being will have within each cell of their body a nucleus containing 23 pairs of chromosomes, half of which are inherited from each parent for a total of 46 chromosomes in every cell of the body (Bull, 2011). The most common form of Down syndrome occurs when an individual is born with a full or partial extra copy of chromosome 21 (trisomy – 21), making the total number of chromosomes 47 in each cell of the body (Bull, 2011). Down syndrome’s characteristics of duplicated genetic material on chromosome 21 alter the course of development. There are 3 different types of Down syndrome:

Trisomy 21 (Nondisjunction)

Trisomy 21 accounts for 95% of cases and is characterized by an error in cell division called “nondisjunction” (NDSS, 1979). Nondisjunction results in, “an embryo with three copies of chromosome 21, instead of the usual 2” (NDSS, 1979). The nondisjunction occurs prior to or at conception; a pair of 21st chromosomes in either the sperm of the egg fails to separate and as the embryo develops, the extra chromosome is replicated in every cell of the body (NDSS, 1979).

Mosaicism

Mosaicism (or mosaic Down syndrome) accounts for about 1% of all cases of Down syndrome (NDSS, 1979). It occurs when nondisjunction of chromosome 21 occurs in one, but not all of the initial cell divisions after fertilization (NDSS, 1979). When this occurs, there is a mixture of two different types of cells, some containing the usual 46 chromosomes and some containing the unusual 47 (NDSS, 1979). Current research has indicated that, “individuals with mosaic Down syndrome may have fewer characteristics of Down syndrome than those with other types of Down syndrome” (NDSS, 1979). However, broad generalizations are not accurate or possible because of the wide range of abilities people with Down syndrome possess.

Translocation

Translocation accounts for about 4% of all cases of Down syndrome. Translocation is characterized by a part of chromosome 21 breaking off during cell division and attaching to another chromosome (typically chromosome 14) (NDSS, 1979). In this type of Down syndrome, the total number of chromosomes in the cells remains 46, but the presence of an extra part of chromosome 21 causes the characteristics of Down syndrome (NDSS, 1979).

Characteristics

The National Institute of Child Health (NICH) states that the characteristics of Down syndrome are:

Physical Differences

  • Small stature
  • Short neck, with excess skin at the back of the neck
  • Small head, ears, and mouth
  • Decreased muscle tone
  • An upward slant to the eyes
  • Flattened, broad face profile
  • White spots on the colored part of the eye (Brushfield spots)
  • Wide, short hands with short fingers
  • A single deep crease across the center of the palm
  • A deep groove between the first and second toes

Intellectual Differences

  • Short attention span
  • Poor judgment
  • Impulsive behavior
  • Slow learning
  • Delayed language and speech development

Each person with Down syndrome is a unique individual and may possess these characteristics to different degrees at different times in their lives, or they may also not exhibit them at all (NICH, 2014).

Signs & Symptoms

When a person is born with Down syndrome, the “signs” of the disorder are typically identified by their physical characteristics. As for symptoms, individuals with Down syndrome are at an increased risk for certain health problems (or comorbidities) depending on whether they are children or adults (these populations face different challenges at different times). Some of the common health conditions children are prone to include:

Physical

1) Hypotonia (poor muscle tone): Poor muscle tone and low strength, which will contribute to delays in motor milestones, such as: rolling over, sitting up, crawling, and walking (Tudella, Pereira, Basso & Savelsbergh, p. 1514, 2011). However, despite these delays, children with Down syndrome can learn to participate in physical activities just like other children (Tudella et al., p. 1514, 2011). The characterized poor muscle tone, combined with a tendency for the tongue to stick out can make feeding an infant with Downs’s syndrome uniquely difficult. Most children with Down syndrome need nutritional supplements to make sure they are getting all of the nutrients that they need (NICH, 2014).

2) Infections: Individuals with Down syndrome are 12X more likely to die from untreated and unmonitored infections than other people (NICH, 2014). A person with Down syndrome will usually have problems with their immune system, making it difficult for the body to fight off infections and therefore it is highly recommended that children with Down syndrome receive all recommended immunizations to help prevent infections (NICH, 2014). Statistically speaking, infants with Down syndrome have a “62-fold higher rate of pneumonia, especially in the first year after birth, than do infants without Down syndrome” (NICH, 2014), which highlights their susceptibility to infections.

3) Problems with the upper part of the spine: Atlantoaxial instability is found in 1 – 2 of every 10 children born with Down syndrome and it is characterized by misshapen bones in the upper part of the spine, underneath the skull (NICH, 2014). It is important to identify this abnormality early to prevent permanent injury. The Atlantoaxial instability must be recognized and accommodated for before the child begins playing sports recreationally or competitively because some have an increased risk of spinal injury. Therefore possible precautions should be discussed with a child's health care provider before participating (NICH, 2014).

Neurological

1) Epilepsy: Individuals with Down syndrome are more likely to have epilepsy. The risk for epilepsy increases with age, but seizures usually occur either during the first 2 years of life or after the third decade of life. Almost one-half of people with Down syndrome who are older than age 50 have epilepsy. The seizures can usually be treated and controlled well with medication (NICH, 2014).

2) Mental health and emotional problems: Often a child with Down syndrome will experience behavioral and emotional problems, including anxiety, depression, and Attention Deficit Hyperactivity Disorder (NICH, 2014). Repetitive movements, aggression, autism, psychosis, or social withdrawal may also be displayed in children with the disorder. However, children with Down syndrome are not more likely to experience these problems, but they are more likely to have difficulty coping with their problems in positive ways, especially during adolescence (NICH, 2014).

Senses

1) Vision problems: Visual problems of a wide range are extremely common in children with Down syndrome (greater than 60%). These problems include cataracts (clouding of the eye lens) that may be present at birth, or develop over time. There are also other eye problems that are more likely in children with Down syndrome, such as, “near-sightedness, “crossed” eyes, and rapid, involuntary eye movements… glasses, surgery, or other treatments will usually improve vision” (NICH, 2014).

2) Hearing loss: An extremely large portion (approximately 70 -75%) of children with Down syndrome has some percentage of hearing loss because of problems in developing ear structures. It is recommended that, “babies with Down syndrome be screened for hearing loss at birth and have regular follow-up hearing exams” (NICH, 2014). These hearing problems can be corrected, but children with Down syndrome (as highlighted above), tend to get a lot of ear infections so they should be monitored closely to prevent any potential hearing loss (NICH, 2014).

Heart

1) Heart defects: Nearly 50% of babies born with Down syndrome are born with congenital heart disease (CHD) as well, the most common type of birth defect (NICH, 2014). CHD is dangerous because it can lead to, “high blood pressure in the lungs, an inability of the heart to effectively and efficiently pump blood, and cyanosis (blue-tinted skin caused by reduced oxygen in the blood)” (NICH, 2014).

Cancer

1) Blood disorders: Leukemia (cancer of the white blood cells) is 10 - 15X more likely to occur in a child with Down syndrome than a child without (NICH, 2014).

Endocrine

1) Hypothyroidism: This occurs when the thyroid makes little or no thyroid hormone, which occurs more often in children with Down syndrome than in children without the disorder (NICH, 2014). One way or another, this causes a disruption in the bodies ability to regulate hormones and therefore temperature and energy amongst other important body mechanisms.

Gastrointestinal

1) Gum disease and dental problems: Teeth tend to develop more slowly, in a different order, and misaligned or fewer in children with Down syndrome (NICH, 2014). Children with Down syndrome also tend to not take very good care of their teeth (poor dental hygiene), which often lead to serious gum disease (NICH, 2014).

2) Digestive problems: Digestive problems are common and range from structural to functional, including defects in development of organs and problems digesting certain types of foods. This often leads to restrictive diets, and even surgery (NICH, 2014).


Each individual with Down syndrome is different and not every person will have additional health problems. As well, many of these associated conditions can be treated with medication, surgery, or other interventions (NICH, 2014). Specifically concerning adults, they are more likely to develop mental health issues such as depression. Individuals with Down syndrome also experience premature ageing which results in a decreased life expectancy, which therefore puts them at an increased risk for premature dementia, memory loss, and impaired judgment similar to that occurring in individuals with Alzheimer disease (NICH, 2014). As well, high cholesterol, obesity, metabolic syndrome, diabetes, cataracts and early menopause are characteristic of Down syndrome (NICH, 2014).

Risk Factors

1) Advancing maternal age: As a woman gets older her chances of giving birth to a child with Down syndrome increases. The older a woman becomes, the older her eggs are which increases the risk of improper chromosome division. The odds are, at age 35, 1 in 350, at age 40, 1 in 100 and at age 45, 1 in 30 (Mayo Clinic, 2014).

2) Having had one child with Down syndrome: The odds of a women having another child with Down syndrome is about 1 in 100 (Mayo Clinic, 2014).

3) Being carriers of the genetic translocation for Down syndrome: Both men and women can pass on the genetic translocation for Down syndrome (Mayo Clinic, 2014).

Diagnosis / Prognosis

The prognosis of Down syndrome is variable depending on the individual. Every person diagnosed will have a different set of comorbidities that need to be treated, making their life expectancy individual to them. That being said, advancements in science and technology have greatly increased the life expectancy’s of those diagnosed with Down syndrome. In the 1900’s, “Down syndrome patients were expected to live less than 10 years” (WHO, 2015). Today, in 2015, approximately 80% of adult Down syndrome patients reach upwards of their 50th birthday and beyond (WHO, 2015). As well, the quality of life of a person with Down syndrome has greatly improved because of proper health care, which includes: “regular check-ups with health professionals to monitor mental and physical growth and to provide timely interventions (therapies)” (WHO, 2015). Proper health care facilitates the individuals “participation in mainstream society and the fulfillment of their personal potential” (WHO, 2015).

There are several different types of diagnosis screening tests available before birth and after birth:

  • Before Birth:
    • Ultra Sound (or sonogram): Used in the first trimester to screen for physical signs of Down syndrome (Filkins & Koos, 2005).
    • Blood Test (or Genetic Test): There are a few different types of tests, but they all involve taking a sample of the mother’s blood. The most common is the alpha-fetoprotein (AFP) test (Filkins & Koos, 2005).
  • Abortion Rates: Approximately 92% of pregnancies with a diagnosis of Down syndrome are terminated (Mansfield, Hopfer, & Marteau, 1999).
  • After Birth:
    • Blood Test (or Genetic Test): Involves taking a blood sample from a newly born baby (Filkins & Koos, 2005).

Cognitive Development

Individuals will Down syndrome experience cognitive abnormalities that result in learning difficulties that lead to delays in many areas of development, but not all areas are affected equally.

  • Relative Difficulties: Children with Down syndrome generally learn and progress slower than most other children. They especially experience difficulties in, “expressive language, grammar and speech clarity, number skills, and verbal short-term memory (NICH, 2014).
  • Relative Strengths: Children with Down syndrome have some areas of development that are not greatly affected including social development, learning with visual supports and word reading (NICH, 2014).

Motor Development

Movement Experiences for Children with Down syndrome

The movement experiences of children with Down syndrome vary from those of typically developing children. Current research concludes that children with Down syndrome have delayed motor milestone achievements when compared to children without Down syndrome (de Campos, Rocha, & Savelsbergh, 2010). This includes both gross motor movements and fine motor movements, which are both equally critical for functional independence (de Campos et al., 2010). Although they are delayed, early intervention movement therapies assist in helping the children develop all of the expected motor movement tasks in the same sequence as other children, just at an overall slower pace. There are two main factors that contribute to the motor delay seen in children with Down syndrome; they are: hypotonia (low muscle tone) and lagmentous laxity, which means “loose ligaments” (Tudella et al., p. 1514, 2011). These two factors specifically result in balance deficits and postural control difficulties, which heavily restrict children’s movements and cause difficulties for them to defy gravity and explore their environment early on in infancy development (Tudella et al., 2011). Most evident is that they have difficulties in performance and in acquiring motor skills in prone, supine, sitting and standing positions. Again, reiterated, these children do achieve the typical level of motor performance seen in most infants, but at a delayed pace, “i.e. acquiring rhythm is slower” (Tudella et al., p. 1514, 2011). Current research by Tudella agrees that (2011), “the sequence of motor development in children with Down syndrome is the same as the typical infants, however infants with Down syndrome need more time to acquire skills” (p. 1514). In children with Down syndrome, the major motor milestone achievements are seen at a delay of at least 1 month in comparison to the typically developing infant (Tudella et al., 2011). Therefore a few of the most important motor milestones in Down syndrome are as follows:

  • Rolling at 6 months (in comparison to typically 4 – 6 months)
  • Independent sitting at 9 months (in comparison to typically between 4 – 7 months)
  • Walking at 19 months (in comparison to typically 9 – 12 months)

In addition, a slowness (delay in reaction time) and a clumsiness quality are observed in children with Down syndrome (Tudella et al., 2011). As well, as the aforementioned hypotonia and lagmentous laxity, there are a few common health conditions associated with children who have Down syndrome that impede their movement experiences. These conditions (comorbidities) impact the individual movement experiences of the children with Down syndrome, and can continue to affect the individual into adulthood (NICH, 2014). Most often, children with Down syndrome can participate in the same activities as typically developing children (NICH, 2014), but they first must overcome their most common health conditions:

  • Spine issues: Will determine what kind of physical activity the child can participate in when they get older (for example, invasive team games are most likely contraindicative) (Bull, 2011).
  • Vision Problems: Will have to be corrected with glasses, contacts or laser eye surgery for optimal visual ability (Bull, 2011).
  • Hearing Loss: Will have to be corrected as much as possible with a hearing aide or cochlear implants (WHO, 2015).
  • Obesity: Children diagnosed with Down syndrome are more likely to become obese as they age and this will have an impact on what physical activity they are capable of performing (Whitt-Glover, O'Neill, & Stettler, 2006).

Participation in Physical Activity

Although only the most common of the additional health conditions seen in Down syndrome are listed here, every heath condition listed in the Sign & Symptoms section of this Wiki Page could negatively affect a child that has Down syndrome and their movement experiences throughout their lifespan (NICH, 2014). These problems will result in negative affects on a child’s movement acquisition and physical activity levels as they age (Whitt-Glover et al., 2006). Strength, agility, postural stability, speed, coordination, and reaction time are the basic skills one needs to be above to develop skills such as throwing, catching, and kicking. With these skills such as throwing one can then proceed to playing sports (Jobling, 1994). It is common for children with Down syndrome to like all kinds of games and enjoy their experience even if they are not successful in terms of scoring goals and winning (Down syndrome Ireland, 2012). It is important for children with Down syndrome to have fun with physical activity as well as develop their skills. Motor skills can be improved in those with Down syndrome when they are given the opportunity to practice (Frith & Frith, 1974). With the slower rate of motor skill development and the common deficits seen in those children with Down syndrome, it is extremely important to create a tailored physical education program suited to their specific needs (Jobling, 1994).

Benefits

Physical activity and movement education helps keep individuals healthy. With the increase in potential physical problems for those with Down syndrome it is even more important that they receive physical education. Body movements that are distorted and/or unnatural place social limitations and can cause pain or injuries for individuals (Barham, 1993). This can cause barriers to integration within the community and prevent efforts by those with Down syndrome to be active participants in the work force, leisure, and recreational settings. Social contacts and networks that are developed from regular participation in physical activities bring social benefits and friendships to those with Down syndrome that can be just as important as the health benefits (Jobling, 1994).

Recommendations for physical activity

Physical education programs for children with Down syndrome should include opportunities to learn about the movement sequences of skills and how these feel. As well, it is important for them to learn the etiquette, strategies, tactics, and rules of sports. A back-to-the-basics approach is beneficial for those with Down syndrome. In most physical education programs the lesson plans are tailored to the individual’s age. However, for those with Down syndrome, this approach does not work since they are delayed in motor development. For children with Down syndrome it is much more effective to identify the basic skills the child needs to work on for a specific skill and work on these components (Jobling, 1994). It is important to give a child with Down syndrome extra time and opportunities to rehearse a given skill so they are able to internalize it (DSI, 2012). When showing a new skill to a child with Down syndrome it helps to present it in a variety of ways, using concrete, practical, and visual materials when possible (DSI, 2012). It is important to teach a child with Down syndrome to apply new skills to many situations, so they can transfer them, for example from the gym to the playground. As well, it is valuable to continue to teach skills so as to preserve them and not let them be overrun by new input (DSI 2012). The opportunities for children to participate in regular physical activity outside school needs to be realistic to the lifestyle of the families and the individuals own independent way of life (Jobling, 1994). The level of involvement can be along a continuum from competitive to recreational or from segregated to integrated (Jobling, 1994).

Strategies to encourage participation in physical education

  • One-on-one support during the course of a game or activity will help a child feel like they are succeeding (DSI, 2012).
  • In situations where children are hesitant to engage in an activity, offer small group alternative activities (DSI, 2012).
  • Advise other children in the class to be patient and to encourage the student with Down syndrome all the time (DSI, 2012).
  • In the lesson use visuals to demonstrate or model the actions and skills required (DSI, 2012).

Inclusive Education

The Individuals with Disabilities Act (IDEA) makes it a right for individuals with disabilities to get free educational services to help them learn as much as they can in an inclusive (non-segregated) environment (Jobling, 1991). Studies show the students with disabilities perform better across their lifespan in inclusive classroom environments (Jobling, 1994). Specifically for those with Down syndrome, the experience in the ‘real’ world helps them to adapt socially and be functionally independent (Jobing, 1991). For health and education practitioners this is an important piece of legislation to be familiar with. Especially in terms of teachers, they need to be knowledgeable of the different types of disabilities they will likely encounter in their students, and be ready to make modifications to their teaching style to accommodate the students with the disabilities (Jobling, 1991).

Treatment

Currently, there is no cure for Down syndrome. However through science and technology, many therapies have been developed to assist individuals with Down syndrome develop as ‘normally’ as possible. That means that there is not a standard treatment for Down syndrome, and an individuals physical and intellectual strengths and limitations need to be determined and accommodated for. According to the National Institute of Child Health, “A child with Down syndrome likely will receive care from a team of health professionals, including, but not limited to, physicians, special educators, speech therapists, occupational therapists, physical therapists, and social workers” (NICH, 2014).

Therapies

Many early intervention therapies have been created to promote the greatest possible development, independence, and productivity for those with Down syndrome. The earlier the intervention, the better the outcome (quality of life) for the individual (NICH, 2014). The abundance of options for treatments and therapies available to those with the disorder, include:

  • Physical Therapy
  • Speech - Language Therapy
  • Occupational Therapy
  • Emotional and Behavioural Therapy

As well, many individuals with Down syndrome see a Dietician and seek out extra Special Education to ‘keep up’ with their peers in school (NICH, 2014).

Statistics

  • In Canada Down syndrome occurs generally in one in every 800 births (CDSS, 2015)
  • In more than 90% of cases, the extra copy of chromosome 21 comes from the mother in the egg (NICH, 2014)
  • In about 4% of the cases, the father provides the extra copy of chromosome 21 through the sperm (NICH, 2014)
  • Trisomy 21 is the cause of about 95% of all Down syndrome cases (NICH, 2014)
  • Mosaicism is the cause of about 1% of all Down syndrome cases (NICH, 2014)
  • Translocation is the cause of about 4% of all Down syndrome cases (NICH, 2014)

Supporting Organizations Promoting Physical Activity

References

  • Barham, P. (1993). Development of skills through adolescence and early adult life. In Down Syndrome (pp. 151-167). Springer US.
  • Brunamonti, E., Pani, P., Papazachariadis, O., Onorati, P., Albertini, G., & Ferraina, S. (2011). Cognitive control of movement in down syndrome. Research in developmental disabilities, 32(5), 1792-1797.
  • Bull, M. J., & the Committee on Genetics. (2011). Health supervision for children with Down syndrome. Pediatrics, 128, 393–406.
  • Charlton, J. L., Ihsen, E., & Oxley, J. (1996). Kinematic characteristics of reaching in children with Down syndrome. Human Movement Science, 15(5), 727-743.
  • de Campos, A. C., Francisco, K. R., Savelsbergh, G. J., & Rocha, N. A. C. F. (2011). How do object size and rigidity affect reaching and grasping in infants with Down syndrome?. Research in developmental disabilities, 32(1), 246-252.
  • de Campos, A. C., Rocha, N. A. C. F., & Savelsbergh, G. J. (2010). Development of reaching and grasping skills in infants with Down syndrome. Research in developmental disabilities, 31(1), 70-80.
  • Down Syndrome Ireland. (2012). Including children with Down Syndrome in your school. Retrieved from http://downsyndrome.ie/wp-content/uploads/2012/08/primary-book.pdf
  • Filkins, K., & Koos, B. J. (2005). Ultrasound and fetal diagnosis. Current Opinion in Obstetrics and Gynecology, 17(2), 185-195.
  • Frith, U., & Frith, C. D. (1974). Specific motor disabilities in Downs syndrome.Journal of Child Psychology and Psychiatry, 15(4), 293-301.
  • Gunn, P. (1993). Characteristics of Down syndrome. In Down Syndrome (pp. 1-17). Springer US.
  • Jobling, A. (1994). Physical education for the person with Down syndrome: More than playing games?. Down Syndrome Research and Practice, 2(1), 31-35.
  • Mansfield, C., Hopfer, S., & Marteau, T. M. (1999). Termination rates after prenatal diagnosis of Down syndrome, spina bifida, anencephaly, and Turner and Klinefelter syndromes: a systematic literature review. Prenatal diagnosis, 19(9), 808-812.
  • Mayo Clinic. (2014). Risk Factors. Diseases and Conditions: Down Syndrome. Retrieved February 27th, 2015, from http://www.mayoclinic.org/diseases-conditions/down-syndrome/basics/risk-factors/con-20020948
  • National Down Syndrome Society. (1979). What Is Down Syndrome? Retrieved February 28, 2015, from http://www.ndss.org/Down-Syndrome/What-Is-Down-Syndrome/
  • National Institute of Child Health. (2014). Down Syndrome: Other FAQs. Retrieved February 28, 2015, from http://www.nichd.nih.gov/health/topics/down/conditioninfo/Pages/faqs.aspx#adults
  • National Institute of Child Health. (2014). What conditions or disorders are commonly associated with Down syndrome? Retrieved February 28, 2015, from http://www.nichd.nih.gov/health/topics/down/conditioninfo/Pages/associated.aspx
  • National Institute of Child Health. (2014). What are common symptoms of Down syndrome? Retrieved February 28, 2015, from http://www.nichd.nih.gov/health/topics/down/conditioninfo/Pages/symptoms.aspx
  • Tudella, E., Pereira, K., Basso, R. P., & Savelsbergh, G. J. (2011). Description of the motor development of 3–12 month old infants with Down syndrome: The influence of the postural body position. Research in Developmental Disabilities, 32(5), 1514-1520.
  • Rigoldi, C., Galli, M., & Albertini, G. (2011). Gait development during lifespan in subjects with Down syndrome. Research in developmental disabilities, 32(1), 158-163.
  • Rigoldi, C., Galli, M., Mainardi, L., Crivellini, M., & Albertini, G. (2011). Postural control in children, teenagers and adults with Down syndrome. Research in Developmental Disabilities, 32(1), 170-175.
  • Rimmer, J. H., Heller, T., Wang, E., & Valerio, I. (2004). Improvements in physical fitness in adults with Down syndrome. Journal Information, 109(2).
  • Roizen, N. J. (2005). Complementary and alternative therapies for Down syndrome. Mental retardation and developmental disabilities research reviews, 11(2), 149-155.
  • Whitt-Glover, M. C., O'Neill, K. L., & Stettler, N. (2006). Physical activity patterns in children with and without Down syndrome. Developmental Neurorehabilitation, 9(2), 158-164.
  • World Health Organization. (2015). Genes and human disease. Retrieved March 1, 2015, from http://www.who.int/genomics/public/geneticdiseases/en/index1.html