Lefties Don’t Die Young After All, Study Reports

A UCLA study due out next month is likely to help answer the question of whether left-handed people die earlier than their right-handed counterparts.

Contrary to the highly publicized claims that a statistical shortage of elderly left-handers in the population means that left-handers die earlier, the UCLA study suggests that there is no significant difference in the death rates of the two groups. The researchers found that many older persons who are classified as right-handers were born lefties, but that their parents and teachers forced them to convert at an early age.

The issue reached new levels of contention two years ago when psychologists Stanley Coren of the University of British Columbia and Diane Halpern of Cal State San Bernardino reported that left-handers in San Bernardino and Riverside counties die an average of about nine years earlier than right-handers. Their report was met with a hail of criticism and was followed closely by a flurry of scientific publications that supported or rebutted their findings.

None of that evidence has swayed believers on either side of the issue, but the new report may have more credibility because it directly addresses the issue that is at the center of the controversy:

Why are there so few left-handers among the elderly in the population?

Coren, Halpern and others argue that some left-handers are more susceptible to disease and that all left-handers are susceptible to the risks of using tools, cars and other implements of a society designed for right-handers. “Left-handers are being eaten by our environment,” Coren said. “They simply don’t live as long.”

The bulk of scientists, however, have long argued that this apparent lack of old left-handers reflects social pressures earlier in this century that caused parents and teachers to force left-handed children to write and eat with their right hands. But there was no proof for this contention--until now.

UCLA psychologist Paul Satz and his colleagues at UCLA and the University of Bergen in Norway took what Satz termed the “rather simple-minded” approach of asking 2,787 people not only which hand they use for a variety of tasks, but also whether they had been made to switch the hand they favored when they were young.

Their results, to be reported in the May issue of the journal Neuropsychologia, show that many people, particularly those who are older than 60, say they were forced to switch as children and that this increased proportion in the older groups largely offsets the decline in incidence of left-handers.

A typical written comment from one of the respondents, an 86-year-old man, noted: “Went to school in the days when they whacked your duke if left-handed, so ended up a pseudo right-hander.” Another woman, age 82, wrote: “I was born left-handed, in those days they switched everybody to right.”

“The left-handers are still present in older populations,” Satz concluded. “They simply show up on most surveys as right-handers.”

“This is a very important paper,” said psychologist Loren Harris of Michigan State University. “I don’t think it will put an end to the controversy, but it should.”

Coren, shown the UCLA report, argues that hand-switching does not account for all the loss of left-handers with increasing age. Satz’s figures still show a small trend toward fewer left-handers in older populations, but it now seems clear, other experts said, that the risk to left-handers is substantially smaller than Coren and Halpern have argued.

The extent of that risk is of more than academic interest. If Coren and others are right, insurance companies might set higher rates for left-handers in the same way that they set higher rates for men because they die earlier than women. Factories and many hand tools might have to be redesigned to prevent product liability suits.

Perhaps most important, Satz said, parents might once more begin forcing their left-handed children to use their right hands. “This issue has terrified some parents,” he said. In light of his new results, however, the message is clear, he said: “Parents should let children develop naturally. . . . Biology is so important. Don’t tamper with it.”

In the population at large, about 9% of women and 13% of men are left-handed, but many studies have shown a peculiar age distribution. At the age of 10, 15% of the population is left-handed. At 20, 13% is left-handed. By age 50, the proportion drops to 5%, and beyond age 80, it is less than 1%.

Scientists are not sure why left-handedness develops. Perhaps as much as half the time, it is genetic--although no one has ever convincingly argued which genes are responsible.

But the other 50% of left-handedness, many researchers argue, is caused by trauma in the womb or at birth. Recent studies have shown that children of mothers who smoke, children who were resuscitated after birth, and children who were twins or triplets are all significantly more likely to be left-handed. Other studies have associated it with prolonged labor, breech birth, prematurity, low birth weight and Rh incompatibility between the mother and fetus.

Individuals with this pathological left-handedness are more prone to a variety of problems, including neuroticism, allergies, insomnia, learning disorders, migraines and immune disorders. And at least two recent studies show that there is a greater incidence of left-handedness among gays and lesbians.

Coren and Halpern argue that all of these conditions increase the likelihood left-handers will die at an early age. They say there is also the increased risk of death from accidents, which has been documented in several studies.

Because of this risk, Coren argues, left-handers die earlier, and he set out to prove it several years ago. An early study of baseball players he conducted showed that left-handers died about four years earlier than right-handers. His study with Halpern showed them dying seven years earlier. And a yet-to-be-published study of 3,165 cricket players by psychologist John Aggleton of the University of Durham in the United Kingdom shows that left-handers die about two years earlier, on average.

But epidemiologists, such as Dr. Jack M. Guralnik of the National Institute on Aging in Bethesda, Md., said that such studies show a “classic fallacy” in epidemiology by looking only at the age of death while not considering age-specific death rates and the percentage of left-handers in each age group.

“It’s like saying that riding a tricycle is more dangerous than sky-diving because the average age of toddlers killed in trike accidents is so much lower than that of sky-divers killed in accidents,” Satz said.

At least four recent studies have examined death rates for left-handers in large populations and found no increased risk of dying young. Researchers such as Guralnik have also recalculated Coren’s and Halpern’s data in an epidemiologically correct fashion and found that it too shows no risk of early death. Coren’s handling of the data has inspired resentment among researchers who study death rates.

“Let psychologists such as Drs. Halpern and Coren study the living and leave mortality analyses to actuaries,” said James J. Murphy, executive vice president of the American Academy of Actuaries.

But all of those analyses begged the question of why there are so few left-handers in the elderly population, leaving open the possibility that Coren is correct. At a news conference earlier this year, Coren said: “They are all presuming a socio-historical trend (such as switching from left- to right-handedness in childhood) that accounts for the disappearance of left-handers. If there was such a trend, their criticisms (of his work) would be correct. But there is no evidence for the trend.”

To determine whether there was a historical trend, Satz and his colleagues studied 2,992 subjects. About half the subjects were males between ages 21 and 58 who were enrolled in the Multicenter AIDS Cohort Study at UCLA. The other half were men and women from a Camarillo retirement community.

They found (see chart) that the proportion of people whose handedness had been switched by parents and teachers increased with age, largely countering the apparent disappearance of lefthanders from the elderly population.

Although the data seems to show a small decline in the prevalence of left-handedness among the elderly, Satz attributes it to an artifact of the study design. The young groups were entirely male, while the older groups were predominantly female.

As convincing as Satz’s data may be, the issue is unlikely to die, Harris said. “We can never prove the null hypothesis--that something isn’t there,” he said. “All we can do is test whether it isn’t there and draw inferences.” And that is often not going to persuade many people, he added. “Epidemiology is bloody complicated.”

A Leftward Drift?

Some researchers argue that left-handers are not as prevalent in older populations because parents and teachers early in this century responded to cultural pressures by forcing naturally left-handed children to become right-handed. A new UCLA study offers the first proof of this contention. The researchers found that the percentage of people who said they switched increases in older age groups, largely--but not totally--offsetting the apparent loss of left-handers in those groups.

AGE %LEFT-HANDED %SWITCHED 21-30 15.5 2.7 31-40 13.0 1.4 41-50 11.8 0.6 51-60 14.0 1.8 61-70 8.0 4.0 71-80 5.0 5.6 81-90 3.8 6.4 91+ 0.0 8.0

--Source: UCLA