|Version 4.0 July 9, 2001|
An understanding of
accessible design begins with an understanding of disability. In the first module of
this course, we will provide an introduction to common impairments that cause disability,
the concept of individual differences, design issues related to disability. We will also
identify management issues related to disability and trends that will affect the
disablement process in the near future.
Spinal cord injuries (SCI): These impairments result from damage to the spinal cord usually caused by an accident although violence can also be a factor. SCI has a higher prevalence among those who are high risk takers, specifically adolescent and young adult males. The higher the injury on the spinal cord, the greater range of functional loss in the body. An individual with a high level SCI in the cervical region may lose all function except the use of their head and neck. Even breathing may be impaired.
At the lower levels, an individual may still be able to walk although they may need braces or other assistive devices. In the mid-region, the loss of function may be restricted to below the waist, which is called paraplegia. Loss of some or all function in all four limbs due to a high level injury is called quadriplegia. If the injury only affects three limbls, it is called tetraplegia.
People with spinal cord injuries that are severe enough to cause inability to walk use wheelchairs for mobility. If limitations affect the upper body enough to make using a manual wheelchair difficult, they will need assistance to move the chair or use a power wheelchair. People with quadriplegia and tetraplegia have limitations in use of their arms and hands as well as their legs. They may have greatly restricted reaching and grasping abilities. The higher the injury, the more difficulty people with SCI will have balancing while reaching from a wheelchair or seated position.
Paralysis: Paralysis of muscles can be caused by many diseases and conditions. However, the most common cause is polio during childhood. Since the advent of polio vaccines in the late 1950's, polio has been practically eradicated in the U.S. However, there are many survivors of polio who are now in their '50's and older. Moreover, there are many survivors of polio in other countries who may immigrate into the U.S. A common result of polio is paraplegia and the need to use a wheelchair and braces.
Because survivors of polio have spent many years adjusting to their disability, they often have very good upper body strength. But, for most individuals, aging with polio results in additional complications, particularly loss of respiratory function. In addition, aging is associated with other disabling conditions that affect the upper body like arthritis. Older people who had polio and were able to walk using crutches and braces often find that they need to use a wheelchair or scooter when they get older.
Neuromuscular diseases. These diseases cause loss of function in the nervous system and muscles. Their onset can be early in life or later. Multiple Sclerosis, for example, has its onset in middle age. These diseases are progressive. At first, the individual may not even appear to have a disability. Later they may have significant visible loss of energy and strength and eventually they will need to use a wheelchair. Motor control such as using hands can be limited significantly. MS has periods of remission when the condition of the individual even improves. These periods should not be mistaken as complete recovery.
Cerebral Palsy. CP is a brain-related disease believed to be caused by a pre-natal condition. CP affects individuals in many different ways, depending on the part of the brain affected. Some individuals with CP have severe mental retardation and/or speech impediments while others have none at all. Some of those with mental retardation have no physical limitations while others have significant physical impairment as well as retardation.
CP is a stable condition and does not change with age. People with CP can have mild or significant limitations in reaching and grasping, walking and other body movements. They often have good strength but those who have spasticity (high muscle tone) may experience uncontrolled movement and rigidity of the muscles and those with flacidity (low muscle tone) can have difficulty exerting force with their extremities. Those individuals with significant upper body limitations will need to use power wheelchairs. CP also causes vision, hearing and speech limitations. Thus, an individual with CP may have a variety of functional limitations.
Traumatic Brain Injury. TBI is caused by a blow to the head, usually in an accident or through violence. As with CP, TBI results in a wide variety of limitations. These limitations are associated with the side of the brain affected. People who have a severe injury can sometimes recover significant function but it may take a long period of rehabilitation, 2-5 years. TBI often occurs in adolescence and young adulthood. Like SCI, it is associated with risk taking behavior. Unlike CP or SCI, TBI is not a stable condition for a few years after the incident. As time goes on, however, further recovery is less likely. Some individuals with TBI may lose the ability to talk and have to converse with a communications board or computer. There may be some significant limitations to intellectual function like memory or decision making. Like CP, TBI can cause sensory limitations as well as physical, mental and communications problems. Balance can also be affected.
Stroke. A cerebral vascular attack or stroke is caused by a blood clot that blocks a blood vessel or artery in the brain, or when a blood vessel in the brain breaks. Like CP and TBI, the specific abilities lost or affected depend on where in the brain the stroke occurs and on the size of the stroke. For example, someone who has a small stroke many experience only minor effects. On the other hand, someone who has a larger stroke may be left paralyzed on one side. Paralysis on one side, or hemiplegia, results in difficulty walking. although usually an individual will be able to stand to a degree. A stroke can affect the speech centers of the brain which results in limitations in communication. It can also affect memory and other mental functions. Although strokes are not uncommon among the adult population in general, there is a strong association with old age.
Heart disease and other cardio-respiratory diseases. Heart disease is one of the most common disabling conditions. There are many causes of heart disease. Heart attacks are most common in the '50's and older. Temporary or permanent damage to heart function due to heart attacks has the most direct impact on function. People who are recovering form a heart attack or who have significant loss of heart function have low stamina and may need to rest often. In addition to heart disease, asthma, emphasema and other cardio-respiratory diseases have a significant impact on functional independence. These diseases limit stamina to the point where individuals may need to use wheelchairs to move about. Although they may be able to stand and walk without assistance, they use these assistive devices to reduce energy expenditure and overcome problems with stamina. Moreover, they may not be able to walk stairs or long distances at all; or, completing these tasks may put them at risk of further damage. People with these conditions have particular difficulty where significant biomechanic effort is required to gain access to buildings like at entry doors and at ramps. Often individuals with these conditions are not easily identifiable.
Arthritis and connective tissue diseases. These diseases affect the joints and surrounding tissue. The prevalence of arthritis in a population is directly associated with age. These diseases can cause pain whenever the joint is stressed (e.g. weight bearing activity, movement). They also can cause swelling that restricts the range of movement in a joint. People with these diseases affecting the lower body may have difficulty walking and, if the conditions is severe enough, they may have to use a wheelchair. Walking stairs may be particularly difficult. Bending to reach low items can also be difficult or impossible. Those for whom the upper body is affected can have difficulty reaching and using controls and hardware, especially if these devices require twisting or a large force to activate.
Blindness. There are many diseases and conditions that cause partial or complete loss of sight including glaucoma, stroke, TBI, retinitis pigmentosa and macular degeneration. Those who have partial losses will have difficulty reading small print, print that does not have good contrast with its background or fonts that are complex and unusual. Those who have complete loss of sight will not be able to read visual signs and instructions at all. Both groups may have difficulty noticing hazards in the path of travel or finding their way on a site or in a building.
People who have vision impairments from early ages develop coping skills such as use of the long cane or reading Braille. However, the frequency of visual impairments is closely associated with age. Older people are not always able to develop such skills to the same degree as other groups. Moreover, the high prevalence of other disabilities among the older population means that older people can often have both sensory and motor impairments.
Hearing impairment. There are many causes of hearing disabilities, including congenital defects, effects of diseases like stroke, accidents, long term exposure to noise and age related losses. Hearing impairments differ in severity from mild high tone losses to complete losses. High tone losses are considered normal to the aging process. Most people over 75 have some high tone hearing loss. Hearing impairments cause difficulty or inability to hear alarms and signals. They can also lead to difficulty hearing speech in public assemblies or classes. Finally, they affect use of telephones and media that rely on sound to communicate information.
It should be noted that there are many other causes of functional impairment that are not on the list above. These represent the most frequently encountered impairments but there are many that have lower incidence but that can have just as serious implications for building use.