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THE BOOMER EFFECT: ACCOMMODATING BOTH AGING-RELATED DISABILITIES AND COMPUTER-RELATED INJURIES

Jane Berliss-Vincent
Center for Accessible Technology
2547 8th St., Suite 12-A
Berkeley, CA 94710
jbvincent@cforat.org

Introduction

Aging baby boomers will represent a significant spike in national demographics. Along with this spike in population will almost inevitably be a spike in the overall number of people with disabilities attributable to the natural processes of aging. For example, there are projected to be more than 3.2 million people with severe visual impairment (functionally defined as the inability to read a newspaper) in 2000, and almost 6 million by 2030. For individuals with any level of vision impairment, the estimate is 4.9 million people in 2000 and over 9 million for 2030. (Crews, 1994) 

There is also a new cause of disability: prolonged and/or improper computer use. International studies show the prevalence of wrist/hand problems among computer users is generally 10-19%, and may reach 40%. (Bammer, 1990) The estimated incidence eyestrain or other visual problems attributable to computer use is between 70 and 88% (Wolff, 1997; Salibello and Nilsen, 1995). At least one professional reports some level of physical discomfort among 60% of his patients that use speech input. (McEvoy, 1999).

The “boomers” will be the first generation to risk dealing en masse with the effects of computer use before or simultaneously with dealing with the effects of aging. Therefore, a need exists to look at both accommodating the inevitable effects of age and preventing the avoidable effects of extensive or improper computer use.

The aging-related disabilities discussed in this paper are natural, predictable consequences of aging that affect vision, the wrists/hands, and the larynx. This paper does not cover the full range of normal aging-related disabilities, such as those related to hearing, nor does it cover common but not inevitable conditions. It also does not cover disabilities with causes besides aging or improper computer use. Finally, it does not cover critical factors such as computing environment (e.g., lighting and furniture) or healthy work practices; for details on these areas, the reader is referred to the author's more comprehensive work on the topic (Berliss-Vincent, 1999).

Vision

Aging-Related Disabilities
Around age 40, the lens becomes thicker and flatter and the pupil becomes less able to change diameter, reducing the amount of light that reaches the retina. The lens hardens, losing some of its ability to change focus between near and distant objects (accommodation) and requiring use of corrective lenses for reading (presbyopia). Sensitivity to glare appears to increase with age. Individuals may be less able to discriminate between certain colors, and sensitivity to contrast may be reduced. There is generally reduction in the size of the visual field. (Morgan, 1986; Werner et al., 1990) A reduction in eye lubrication is also associated with age, particularly for menopausal and post-menopausal women. (Roberts, 1991; Group Health Cooperative, 1996)

Computer Use Injuries
There appears to be a strong correlation between video display terminal (VDT) use and transient eye problems, such as pain or discomfort, light sensitivity, insufficient or excessive production of tears, and redness. (Bergqvist et al., 1990; Yagimura et al, 1990). Age also appears to play a role, with reported problems increasing among older individuals. (Meyer et al., 1990;Ong and Phoon, 1987)

The American Optometric Association (1997) identifies three main causes of computer eyestrain: frequent, long saccadic movements (the “jumps” the eye makes when reading text), continuous accommodation changes, and continuous changes in alignment (vergence). These movements stress the visual system, particularly the musculature.

Computer Design Considerations

Wrists/Hands

Aging-Related Disabilities
With age, muscle strength decreases; by the time an individual reaches 60, their strength has generally decreased 15-25% from peak strength at age 35. The muscles in the hand may be particularly affected. (Abrams et al., 1995; Grandjean, 1988) Nerve conduction velocity also tends to become slower with age. (Albert, date?)
Computer Use Injuries
Typing speed appears to play a role in occurrence of repetitive strain injuries (RSI). Guggenbuhl and Krueger (1990)found that more than 4 key presses per second put an extensive load on the fingers’ flexor muscles and increased the load on forearm muscles. Key activation pressure may also cause injury; Rempel et al. (1991) found that the force used to activate keys was often 300% greater than necessary. In addition,Ong and Phoon (1987) found that keystrokes per hour decreased with age, from 14K at age 25 to 10K at age 45.

Cursor control devices (mice, trackballs, etc.) may also be a cause of RSI. Injuries to the wrist are likely due to unnatural positioning; injuries to the fingers are likely due to stress on the tendons from clicking and/or dragging. (Hagberg, 1995)

Computer Design Considerations

Larynx

Aging-Related Disabilities
In the aging individual, the larynx tends to become less moist and the laryngeal cartilage becomes more rigid. The vocal cords themselves may “bow” due to atrophy of the inner muscles and loss of the exterior pad of fat, causing the vocal cords to close incompletely and resulting in a breathy vocal quality. There are also significant changes related to gender: older men’s vocal cords become thinner, resulting in higher-pitched voices, while women’s cords become thicker after menopause, resulting in lower pitches. The production of speech may also be affected by other losses in functional capability; for example, older individuals may strain their vocal cords in an effort to compensate for reductions in lung capacity. (Sinard and Hall, 1998; Abrams et al., 1995; Tanner, 1997)

Computer Use Injuries
There is significant anecdotal information suggesting that there may be deleterious effects on the voice caused by improper use of either type of speech input. (e.g., Fox, 1998) To date, however, there appear to be only one published study specifically on the effects of speech input on the vocal mechanism. (Singer, 1999; Postma, 1999) This study (Kambeyanda et al., 1996; Kambeyanda et al., 1997) indicated diagnoses of bowed vocal chords, vocal fatigue, chronic hoarseness, and vocal abuse among a small sample of speech input users, as well as anecdotal reports of problems from speech input users.

Computer Design Considerations

Conclusion

Like most computer modifications, modifications designed to meet the needs of older computer users will likely be greeted with acceptance and even enthusiasm by all users for the increased level of comfort they can provide. Flexibility and ease of modification are key to ongoing comfortable and safe computer use.

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