People who live in the colored areas on the map above have an unusually high chance of getting endemic goitre. Doctors can now pinpoint many other diseases geographically. This is a report on what science knows about these variations, and why some doctors are convinced that environment may be the key to most disease
PERHAPS the world's first “epidemiologist” was a physician named John Snow who practised in London, England, in the middle of the last century. In 1848 Snow discovered that most of the people suffering from a new and serious outbreak of cholera got their drinking water from one pump on Broad Street. Although he knew nothing about bacteria, Snow reasoned that contaminated water must in some way be responsible. Without consulting anyone, he went down to Broad Street one dark night and took away the pump handle. Soon, the outbreak subsided.
Epidemiology has moved slowly forward ever since, until now. in the age of computers and whole galaxies of statistics, it is one of the most exciting fields of knowledge in medicine. Many doctors are now convinced that where people live, and what kind of life they lead, are responsible for afflictions as widely varied as cancer and bad teeth. “Social and economic environment.” says Dr. W. H. le Riche, head of the department of epidemiology at the University of Toronto, “is far more important than medical environment in the incidence and control of disease.”
Epidemiology is not, now, the study of epidemics alone. It is a kind of medical research that probes into the hows, whys and — particularly — wheres of all disease. Much of the news that seeps out from the epidemiologists’ labs concerns new facts they have discerned. But perhaps more important are the new questions that epidemiology is teaching doctors to ask. Why, for instance, do women in Quebec show an incidence of cancer of the breast and cervix twice as high as women in Saskatchewan? Why docs tuberculosis strike students in Ontario more frequently than any other occupation group? Why do babies born in Saskatchewan and Alberta have a higher rate of respiratory troubles than those born in the east? Why does Newfoundland have twice as high a rate of stomach cancer as the rest of the country? Why do some malignancies seem to have a relation to altitude?
And so on. The breakthrough to these inklings of new knowledge has come with the age of cybernetics. The advent of the computer has given medical researchers a
chance to examine what is in effect a vast body of new clues to what causes disease — and it is obvious already that these new clues will lead to some new solutions.
Leukemia, for instance, has increased mysteriously during the past thirty years. In England, mortality from leukemia has risen from seventeen in every million people in 1931 to fifty in every million in 1956; in Canada it has gone up from thirty-one per million in 1940 to fifty-one in 1954. In a recent compilation of all known leukemia studies to date F. G. J. Hayhoe of Cambridge University noted that the disease seems to be associated with social groups that get a high degree of medical care. Leukemia also apparently strikes more often among the well-to-do than among the poor; in Britain, twice as often among the upper income classes. Hayhoe reasons that both these facts may indicate that the larger amounts of clinical X-ray and of some drugs that are given to people who are well served by doctors may have something to do with leukemia — and it is this sort of clue that epidemiology holds out for many diseases.
At Roswell Park Memorial Institute, the
continued on page 42
continued from page 24
Could leukemia be linked to a family’s size, where it lives or the kind of pets it keeps?
famous cancer research hospital in Buffalo, N.Y., an IBM 1620 calculator is being used in the detective work involved in tracing the causes of leukemia. One fact that has recently conic to light is that the disease has a tendency to cluster in geographic areas. The state of Michigan recently reported an outbreak of twenty-two cases in one relatively small part of the state. The Roswell Park researchers have found one square mile in the Buffalo district that has an unusual proportion of leukemia cases. This raises two possibilities: one, that a virus may be involved — a theory that laboratory researchers are working on — or, two, that natural radiation in the environment may be a factor. Roswell Park doctors have found some interesting information about the relationship between the amount of natural radiation absorbed by parents and the chances of a child having leukemia. But — as in most epidemiological studies — the researchers arc seeking other links as well. Patients or their next of kin (a tragic aspect of the leukemia study was that only twenty percent of the reported patients were still alive when the Roswell Park survey was finished) have been asked about previous infections, inoculations, the number of places they’d lived, what pets they'd kept and the size of their families, among many other questions. The computer will try to extract some meaningful conclusions from the replies.
There is now great interest among doctors in the effects of natural radiation. A few years ago the health officer of Washington County, Maryland, looked over the cancer death records of the county back to 1898. He noticed a disproportionate number of deaths in certain areas. Thus began a research project, in co-operation with the field studies section of the U. S. National Cancer Institute, to look for any environmental differences which might yield a due as to why the number of cancer deaths had been consistently two to five times higher in some electoral districts than others. Researchers could find no telling differences in cither occupations or background of the people in the various districts. But geological maps showed great variety in rock and soil formation. The county is ribbed with outcrops of vertical folded rock, about two billion years old, and seismic readings showed a tenfold difference in the gamma radiation background of various rock and soil strata. A preliminary survey related the high number of cancer deaths to the high radiation readings. Since then the research group has had the U. S. Geological Survey make an aerial radiation survey of the county, pinpointing the peaks and valleys of radiation background. In Hagerstown, the county seat, a five - year project is now in progress, analyzing soil, rock, water and air samples from
all districts for trace elements as well as radioactive material, to match with cancer-mortality figures.
Somewhat similar surveys are in progress in England, Sweden, The Netherlands, India and Denmark. They suggest that an epidemiological breakthrough can come from any science. Geology or agriculture, rather than medicine, may hold the key to the mysteries of disease occurrence. And significant findings can easily start with insignificant local observations.
Sometimes a geographic tie to disease is obvious and easily explained. The map of North America printed with this report shows the incidence of endemic goitre: high along the western mountain regions, the south shores of the Great Lakes, through New England and south through the Appalachians, but low through much of northeastern Canada and the U.S. southwest. Epidemiologists have noted that goitre invariably occurs on glaciated or flooded soils, sometimes the result of geological movements a million or more years old, which have left them deficient in iodine. The most goitre-prone regions in the world are alpine valleys including those of the Canadian Rockies. Fifty years ago, settlers in the Pemberton Valley, about sixty miles inland from Vancouver, found themselves and their stock suffering so severely from goitre that they were on the verge of packing up and leaving the region. Today, with iodized food and water, the valley and its inhabitants are thriving.
The deadly dangers of sunshine
Cancer still holds the widest interest for epidemiologists. Skin cancer, for instance, seems to vary directly with the amount of sunshine absorbed by the body — among whites, at any rate. With large amounts of sunlight and a nearly all-white population, Australia has the highest skin-cancer rate in the world. A survey of ten U. S. cities showed the incidence of skin cancer grows higher as one moves south on a map.
But not many findings of the epidemiologists arc so easily explained. If Quebec’s higher incidence of cancer of the cervix, quoted earlier, results from women in Quebec bearing larger families than women in Saskatchewan, why is cancer of the breast — usually more prevalent in single women — also found more often in Quebec? Or if the high degree of tuberculosis among students is partly the result, as some doctors believe, of a psychosomatic reaction to the confusion of their lives, why is the morbidity rate from TB higher among unskilled workers in Ontario than it is among people in the professional ranks?
Even diabetes, once thought mainly hereditary, may prove to have some environmental base. Diabetes varies in different countries, and environment seems to affect the age of onset. The Canadian Diabetic Association is now questioning as many of the one hundred and eighty thousand known Canadian diabetics as it can find about such things as the kind of life they lead and what factors appear to have brought on their condition. The CDA hopes to find out, among other things, whether or not diabetes is re-
lated to emotional stress, and whether environment can affect one’s chances of becoming diabetic.
Another ripe field for epidemiological research is the relation of soil constituents — notably nitrates — to respiratory diseases in babies. This may be the explanation for the difference in incidence in the east and west that I referred to earlier. The soils in the west are high in concentration of nitrates, which are known to affect the blood, but, of course, the exact link between soil condition and babies' lungs is something only further research can determine.
Soil conditions may have an affect on dental health too. A recent survey of Oregon school children showed that those who live in areas where there is a concentration of selenium, a natural element in some soils, have worse teeth than those living where there is little or no selenium. And epidemiologists have also noted that some elements in water, notably calcium carbonate, appear to have a greater effect in promoting tooth decay than fluorides have in preventing it.
A detailed survey of Royal Australian Air Force personnel a few years ago showed another interesting variation: recruits from west and
south Australia, where the air is dry and the sun shines an average of more than seven hours a day, had significantly better teeth than those from Tasmania and Victoria, where the climate is damp, with only about two thirds the sunshine of the south. This is not taken to mean that sun determines tooth health, per se. Rather, researchers suggest, climate dictates eating habits, and people usually eat more decay - producing carbohydrates in damp, cool climates. Inland waters are generally harder and contain more carbohydrates than water near the sea. The effect diet can have on tooth health was shown dramatically in studies of European children during and after the Second World War. In Scandinavia, Britain, France and Germany, children’s teeth were in far better condition after years of war rations than they had been previously.
Epidemiologists are also probing the field of mental health—where the effects of environment are sometimes even more obvious than in physical afflictions. As just one example from hundreds that interest doctors involved in the field: researchers in Nova Scotia have found serious psychiatric disorders almost twice as prevalent in communities that are loosely knit and isolated as in those described as “close-knit and integrated.’’ Behind all facts of this sort, of course, are the whys, and the answers will not be easy to find. The important thing now is that the facts and figures from which the questions can be asked
are coming ever more quickly to light.
One of the future problems of epidemiology, particularly now that computers can sift a multitude of data with lightning speed, may be where to draw the line in determining what relationships to study. In its patient questionnaires, which form the bulk of its study data, Roswell Park Hospital asks patients not only what they eat but how often, and how the food is prepared; if they have ever used hormone creams; the jobs they have
had; all the places they and their parents have lived; detailed smoking and drinking habits (Do you puff more at the beginning or the end of a cigarette? How much beer did you drink last month?); and other, often apparently irrelevant, details in a list of ninety-nine questions.
One doctor in Toronto, talking of epidemiology gone wild, told me people have come to the National Cancer Institute of Canada with "perfectly plausible," documented argu-
ments to show lung cancer growth is directly proportionate to the growth of hydro electric power over the last twenty years. Yet when I mentioned this to a doctor at Roswell Park, as an example of ridiculous research in the name of epidemiology, he answered half-seriously, “Don't be too sure,” and went on to remind me how outlandish people used to think was the idea of shipboard rats having any connection with the sailors' bubonic plague. ★
The story you want is part of the Maclean’s Archives. To access it, log in here or sign up for your free 30-day trial.
Experience anything and everything Maclean's has ever published — over 3,500 issues and 150,000 articles, images and advertisements — since 1905. Browse on your own, or explore our curated collections and timely recommendations.WATCH THIS VIDEO for highlights of everything the Maclean's Archives has to offer.