Computers and Health
COMPUTERS AND HEALTH
INDIVIDUAL AND lNSTITUTIONAL
PROTECTIVE MEASURES
CARPAL TUNNEL SYNDROME
Created
by
Andrey Tarassov
Tallinn 1999
ithin the past two years,
substantial media attention has been directed at potential adverse
health effects of long-term computer use. Renewed concerns about radiation, combined
with reports of newly-recognized "repetitive stress injuries" such as
carpal tunnel syndrome, have led some to call for regulation in the workplace
and others to rearrange their offices and computer labs. There is
little evidence that computer use is on the decline, however. On the contrary,
more people are spending more time doing more tasks with computers -- and
faculty, students and staff at colleges and universities have some of the most
computer-intensive work styles in the world.
If, as is widely suspected,
health effects are cumulative, then many of us are at risk in our offices,
labs, dormitories, and homes. Unfortunately, many years will be required before
epidemiological studies can provide definitive guidelines for computer users,
managers, furniture suppliers, and office designers. In the interim,
individuals and institutions must educate themselves about these issues and
protective measures.
One set of issues concerns
workstation design, setup, and illumination, together with users' work habits.
The City of San Francisco, which recently enacted worker safety legislation,
cited research by the National Institute of Occupational Safety and Health
(NIOSH) into VDT operator complaints of eyestrain, headaches, general malaise,
and other visual and musculoskeletal problems as the
rationale for imposing workplace standards, to be phased in over the next four
years.
A second set of issues
relates to suspected radiation hazards, including miscarriage and cancer. A
special concern with radiation is that nearby colleagues could be affected as
well, since radiation is emitted from the backs and sides of some terminals.
The most recent NIOSH study is reassuring, but some caution still seems
prudent.
Ergonomics and work habits
Most people can ride any
bicycle on flat ground for a short distance with no problems. On a fifty mile
ride over hilly terrain, however, minor adjustments in seat height, handlebar
angle, and the like can mean the difference between top performance and severe
pain. Similarly, occasional computer users may notice no ill effects from
poorly designed or badly adjusted workstations, whereas those who spend several
hours a day for many years should pay careful attention to ergonomics, the
study
of man-machine interfaces.
The key to most workstation
comfort guidelines is adjustability--to accommodate different body dimensions,
personal workstyle preferences, and the need to change positions to avoid
fatigue. A recommended working posture shows the body directly facing the
keyboard and terminal, back straight, feet flat on the floor, eyes aligned at
or slightly below the top of the screen, and thighs, forearms, wrists, and
hands roughly parallel to the floor. Achieving this posture may require:
·
A chair with a seat pan that
adjusts both vertically and fore-and-aft, an adjustable height backrest, and
adjustable tilting tension
·
An adjustable height work surface
or separate keyboard/mouse tray (note that many keyboard trays are too narrow
to accommodate a mouse pad, leaving the mouse at an awkward height or reach on
the desktop)
·
A height adjustment for the video
display (a good use for those manuals you'll never read!)
·
An adjustable document holder to
minimize head movement and eyestrain
·
Adjustable foot rests, arms rests,
and/or wrist rests.
with colleagues. A posture
cushion, which maintains the natural curvature of the spine and pelvis while
supporting the lumbar region, may also prove helpful. It should be noted that
any adjustment may feel uncomfortable for a week or so while your body
readjusts itself.
(Some people have been
advised by their physicians to use a backless "Balans" chair, which
minimizes compression of the spine and shifts the body weight forward with the
aid of a shin rest. This posture may be uncomfortable, however, since it
requires stronger abdominal and leg muscles than conventional sitting
positions. The Balans chair is not recommended for overweight or exceptionally
tall persons)
Light and glare
Eyestrain, headaches, and
impaired vision are often a product of improper illumination resulting in
glare, which is light within the field of vision that is brighter than other
objects to which the eyes are adapted. Both direct glare from sunlight and
lighting fixtures directed at the user's eyes and indirect glare due to
reflections from
video screens or glossy
surfaces are common problems for VDT users.
Many offices are too bright
for computer use, which may be a carryover from the days when paperwork
required such brightness or the result of many office workers' preferences for
sunlight and open windows. A NIOSH study recommends 200-500 lux for general
office work; other sources suggest 500-700 lux for light characters on dark
monitors and somewhat more for dark-on-light. If documents are not sufficiently
illuminated, desk lights are recommended in preference to ceiling lights, which
increase reflections from
video screens. Reducing overhead lighting could also result in substantial
energy savings.
VDT workstation placement is
also important. Terminal screens should be positioned at right angles to
windows, so sunlight is neither directly behind the monitor nor behind the
operator, where it will reflect off the screen. If this is infeasible, blinds
or drapes should be installed. Screens should also be positioned between rows
of overhead fixtures, which can be fitted with baffles or parabolic louvers to
project light downward rather than horizontally into the eyes or terminal
screens.
Some users have found filters
placed in front of the screen to be effective in reducing reflections, however
some dimming or blurring of the display may result. Experts 1advise
trial and error, since the best solution appears to depend upon specific
conditions and user preferences. Finally, if you wear glasses or contact
lenses, be sure your physician is aware of the amount of terminal work you do;
special lenses are sometimes necessary. Bifocals, in particular, are not
recommended for extensive terminal work, since the unnatural neck position
compresses the cervical vertebrae..
Breaks and exercises
Working in the same position
for too long causes tension buildup and is thought to increase the risk of repetitive
motion injuries, such as carpal tunnel syndrome. Remedies include changing
postures frequently, performing other work interspersed with computing (some
studies recommend a 10-15 minute break from the keyboard every hour), and doing
exercises such as tightening and releasing fists and rotating arms and hands to
increase circulation. Be aware, also, that the extra stress created by deadline
pressure exacerbates the effects of long hours at the computer.
Radiation hazards
For at least a decade, concerns
have been raised about possible effects of radiation from video display
terminals, including cancer and miscarriages. Earlier fears about ionizing
radiation, such as X rays,
have been laid to rest, since
these rays are blocked by modern glass screens. Also well below exposure
standards are ultraviolet, infrared, and ultrasound radiation.
More recent controversy
surrounds very low frequency (VLF) and extremely low frequency (ELF)
electromagnetic radiation produced by video displays' horizontal and vertical
deflection circuits, respectively. Researchers have reported a number of ways
that electromagnetic fields can affect biological functions, including changes
in hormone levels, alterations in binding of ions to cell membranes, and
modification of
biochemical processes inside
the cell. It is not clear, however, whether these biological effects translate
into health effects.
Several epidemiological
studies have found a correlation between VDT use and adverse pregnancy
outcomes, whereas other studies found no effect. The most recent analysis,
published this year by NIOSH, found no increased risk of spontaneous abortions
associated with VDT use and exposure to electromagnetic fields in a survey of
2,430 telephone operators. This study, which measured actual electromagnetic
field strength rather than relying on retrospective estimates, seems the most
trustworthy to date. The authors note, however, that they surveyed only women
between 18 and 33 years of age and did not address physical or psychological stress
factors.
A 1990 Macworld article by
noted industry critic, Paul Brodeur, proposed that users maintain the following
distances to minimize VLF and ELF exposure:
·
28 inches or more from the video
screen
·
48 inches or more from the sides
and backs of any VDTs.
Although these guidelines seem overly cautious, a
fundamental principle is that magnetic field strength diminishes rapidly with
distance. Users could, for example, select fonts with larger point sizes to
permit working farther from the screen. Remember that magnetic fields penetrate
walls.
Over-reaction to ELF and VLF radiation can also compromise
ergonomics. In a campus computer lab, for example, all displays and keyboards
were angled thirty degrees from the front of desktops to reduce the radiation
exposure of students behind the machines. The risks of poor working posture in
this case appear to be greater than the radiation risks.
A final form of radiation,
static electric, can cause discomfort by bombarding the user with ions that
attract dust particles, leading to eye and skin irritations. Anti-static pads,
increasing humidity, and grounded glare screens are effective remedies for
these symptoms.
To monitor
research and develop institutional guidelines, the University of Pennsylvania
has created a Task Force on Computing in the Workplace, with representatives
from the Offices of Environmental Health and Safety, Fire and Occupational
Safety, Information Systems and Computing, Radiation Safety, Purchasing,
University Life as well as staff and faculty from the Wharton School and
Schools of Engineering, Medicine and Nursing. Interested readers are welcome to
contact the authors for information on the Task Force and its work.
Until more
conclusive research becomes available, individuals, departments, and
institutions will have to weigh the evidence and make their own decisions about
protective measures to minimize the risks of computing. And, in our opinion,
the information technology managers and their vendor partners who provided the
leadership to computerize our campuses, now owe it to their colleagues to work
with epidemiology and ergonomics experts to create computer-intensive
environments that are both productive and healthful.
Avoiding carpal tunnel syndrome:
A guide for computer keyboard users
Carpal tunnel syndrome (CTS) is a
painful, debilitating condition. It involves the median nerve and the flexor
tendons that extend from the forearm into the hand through a "tunnel"
made up of the wrist bones, or carpals, and the transverse carpal ligament. As
you move your hand and fingers, the flexor tendons rub against the sides of the
tunnel. This rubbing can cause irritation of the tendons, causing them to
swell. When the tendons swell they apply pressure to the median nerve. The
result can be tingling, numbness, and eventually debilitating pain.
CTS affects
workers in many fields. It is common among draftsmen, meatcutters, secretaries,
musicians, assembly-line workers, computer users, automotive repair workers,
and many others. CTS can be treated with steroids, anti-inflammatories, or
physical therapy, or with surgery to loosen the transverse carpal ligament.
Recovery of wrist and hand function is often, but not always, complete.
Causes
Like many skeletomuscular disorders, CTS
has a variety of causes. It is most often the result of a combination of
factors. Among these are:
Genetic
predisposition. Certain people are more likely than others to get CTS. The
amount of natural lubrication of the flexor tendons varies from person to
person. The less lubrication, the more likely is CTS. One study has related the
cross-sectional shape of the wrist, and the associated geometry of the carpal
tunnel, to CTS. Certain tunnel geometries are more susceptible to tendon
irritation.
Health and
lifestyle. People with diabetes, gout, and rheumatoid arthritis are more prone
than others to develop CTS, as are those experiencing the hormonal changes
related to pregnancy, menopause, and the use of birth control pills. Job stress
has also been linked to an increased likelihood of CTS. And CTS seems to be
more frequent among alcoholics.
Repetitive motion.
The most common cause of CTS that's been attributed to the workplace is
repetitive motion. When you flex your hand or fingers the flexor tendons rub
against the walls of the carpal tunnel. If you allow your hand time to recover,
this rubbing is not likely to lead to irritation. The amount of recovery time
you need varies from fractions of a second to minutes, depending on many
circumstances, including the genetic and health factors mentioned above, as
well as the intensity of the flexing, the weight of any objects in your hand,
and the extent to which you bend your wrist during flexing.
Trauma. A blow to
the wrist or forearm can make the tendons swell and cause or encourage the
onset of CTS.
Prevention
Computer keyboard
users can take several steps to lower their chances of developing CTS. Some of
these center around the configuration of the workplace, or
"ergonomics." Others have to do with human factors.
Ergonomics. Proper
seating is crucial to good ergonomics. The height of your seat and the position
of your backrest should be adjustable. The chair should be on wheels so you can
move it easily. Arm rests on the chair, though optional, are often helpful.
Table height. To
adjust the chair properly, look first at the height of the table or desk
surface on which your keyboard rests. On the average, a height of 27-29 inches
above the floor is recommended. Taller people will prefer slightly higher
tables than do shorter people. If you can adjust your table, set your waist
angle at 90 degree, then adjust your table so that your elbow makes a 90 degree
angle when your hands are on the keyboard.
Wrist angle. If
your keyboard is positioned properly your wrists should be able to rest
comfortably on the table in front of it. Some keyboards are so
"thick" that they require you to bend your hands uncomfortably upward
to reach the keys. If so, it will help to place a raised wrist rest on the
table in front of the keyboard. A keyboard that requires you to bend your
wrists is a common cause of CTS among computer users.
Elbow angle. With
your hands resting comfortably at the keyboard and your upper arms vertical,
measure the angle between your forearm and your upper arm (the elbow angle). If
it is less than 90 degree, raise the seat of your chair. If the angle is
greater than 90 degree, lower the seat. Try to hold your elbows close to your
sides to help minimize "ulnar displacement" - the sideways bending of
the wrist (as when reaching for the "Z" key).
Waist angle. With
your elbow angle at 90 degree, measure the angle between your upper legs and
your spine (the waist angle). This too should be about 90 degree. If it is less
than 90 degree, your chair may be too low (and your knees too high). Otherwise,
you may need to alter the position of the backrest or adjust your own posture
(nothing provides better support than sitting up straight). (Note: If making
your waist angle 90 degree changes your elbow angle, you may need to readjust
the height of your chair or table.)
Feet. With your
elbows and waist at 90 degree angles, your feet should rest comfortably flat on
the floor. If they don't, adjust your chair and table height and repeat the
steps above. If your table isn't adjustable and your feet don't comfortably
reach the floor, a
raised footrest can help. Otherwise, you may need a different table.
Work routine
You need very
little recovery time between keystrokes to cool and lubricate the flexor
tendons. If you type constantly, however, the need for recovery builds.
Further, working with your hands bent upward at the wrists or frequently
bending your wrists sideways heightens the friction within the carpal tunnel.
It takes longer to recover from these motions. Working under stress (deadline
pressure, anger, or other anxiety) can make matters even worse.
Many studies
recommend a 10-15 minute break each hour to give yourself the recovery time you
need. This needn't be a break from productive activities - just a break from
your keyboard. Exercises can help, too. Try the following:
a) Make tight
fists, hold for one second, then stretch your fingers out wide and hold for
five seconds. Repeat several times.
Variety is the
key. CTS occurs most frequently in workers whose motions are not only
repetitious but are kept up for hours at a time. If you use a keyboard,
structure your workdays to include a mix of activities each hour. For example,
instead of typing all morning and filing all afternoon, mix typing and filing
throughout the day.
Early detection
The most painful
cases of CTS are those that have gone undetected or untreated over a long time.
CTS can be caught easily in its early stages, however, and much of the pain and
all of the disability avoided.
Early symptoms
include a tingling in the fingers, often beginning several hours after work
activity has stopped. Because of this delay in the appearance of symptoms, many
CTS sufferers don't make the connection between their work activities and the
pain they feel until it's too late. The tingling can lead, over time, to
stiffness and numbness in the fingers and hand, and then to severe wrist and
hand pain.
For many
individuals the early symptoms of CTS go unnoticed. Employers and co-workers
can help one another identify the onset of CTS by watching for and pointing out
any unconscious shaking of the hands, rubbing of the wrists, or unusual
postures or hand positions at the keyboard.
At the first sign
of CTS, you should be examined by a doctor who specializes in hand and wrist
disorders. The doctor can perform a number of simple tests to detect CTS, and
can prescribe specific steps for avoiding the problem.
Summary
Carpal tunnel
syndrome is common among computer keyboard users. It can strike anyone, and its
consequences are serious. Awareness of the problem and its causes is crucial to
preventing CTS. With proper ergonomics and attention to the work routine you
can prevent CTS; with early detection and treatment it need never become
debilitating. The employer's attention to stress levels, proper ergonomics, and
the early warning signs of CTS are important in keeping the ailment at bay in
the workplace.
Summary
We hear a lot
about hazards associated with working with computers, and learn from experience
that long hours at the keyboard can bring on eyestrain and various aches and
pains. These concerns, and the steps we can take to make computer work safer
and more
comfortable are the subject of many books and articles.
The good news is that problems can be
avoided through well-designed offices, properly set-up workstations, and
sensible work habits. Checklists and guidelines for setting up and using
computers abound. The bad news: there is substantial variation in opinion as to
what constitutes proper workstation set-up, quick and easy solutions to
ergonomic problems are not always possible, and checklists don't capture the
complexities of the possible combinations of people, task, equipment, and
workspace. Fortunately, there are measures that really do work. A few quick and
universally agreed upon precautions:
·
Use the minimum force necessary to press the
keys.
·
Vary your tasks during the day to avoid sitting
in one position for several hours or performing the same hand motions without
interruption.
·
Take periodic breaks.
·
Keep your wrists in a natural, unforced,
straight position.
Bibliography of
computer and health materials
·
Ross, Randy. "VDTs: Are They Safe?"
PC/Computing . March, 1989, pp. 146-7.
·
Sheehan, Mark. "Avoiding carpal tunnel
syndrome: A guide for computer keyboard users," University Computing Times
(Indiana University, Bloomington). July-August 1990, pp. 17-19.
·
Updegrove, Kimberly H., Daniel A. Updegrove.
"Computers and Health - Issues and Protective Measures." Penn
Printout. February, 1991.