IS THE INCREASE OF CANCER REAL OR APPARENT?

Transcription

1 IS THE INCREASE OF CANCER REAL OR APPARENT? A STUDY BASED ON THE STATISTICS OF CANADA MADGE THURLOW MACKLIN, M.D. Medical School, University of We8tern Ontario, London, Canada The statement is frequently encountered that cancer is rapidly increasing throughout the world, the figures which are brought forward to support this statement being the death rates from this disease per 100,000 of population. The percentage of total deaths which is attributable to cancer may be higher than it was formerly, but that is not in itself evidence that cancer as such is on the increase. A higher percentage of cancer cases may be due to the decrease of other causes of death. The death rates per 100,000 of population, however, are more convincing. Thus in all Canada in 1901 the death rate from cancer per 100,000 of population was 46.8; in the next two decades it had risen to 75 per 100,000 of the population, an increase of 62 per cent. Is the Increase a Real One? This greater frequency has been said by some to be more apparent than real; by others it has been held to be an actual increase. Various arguments are put forward by those who do not admit a real increase. In the first place, they state that the age of death has been raised, so that more people now live to the cancer age than formerly. In this connection they point to the great saving in lives of infants by social and medical agencies, so that they may live to the age at which cancer will develop. Secondly, there is put forward the idea that diagnosis is much better today than it was twenty years ago, so that more cases of cancer are diagnosed than was possible at that time. In the third place, vital statistics are increasingly accurate, another factor which tends to increase the number of deaths attributed to cancer. A fourth argument, which is really a part of the two preceding ones, might be presented, namely, that many more persons are attended by physicians today than was the case in HlOl. With each year each of these factors operates in such a manner as to enhance still further the cancer death rate. Thus each year sees more infant welfare work undertaken, and a lowering of the death rate in the early years of life. Each year sees a progressively higher percentage of well trained personnel in the medical profession. Each year sees a 1193

2 1194 MADGE THURLOW MACKLIN spreading of medical attendance to a greater percentage of the population and to more and more outlying districts, with the result that statistics are becoming more and more reliable. For these reasons we should expect a steady increase of registered deaths from cancer, and from 1921, when the rate was 75, to 1929, the latest year for which Canadian statistics are available, this expectation has been fulfilled, for the rate has steadily risen until it was 90 per 100,000 for all Canada. If only the registration area of Canada as it was in 1921 be considered, the rate is 93.9 for There are observations, also, which lead us to the conclusion that the increase in cancer is more apparent than real. Thus, for example, in 1928 Prince Edward Island had a cancer rate of 114, while Saskatchewan had a rate of only 55, or less than half that of the former province. When, however, we consider the age of the population in the two provinces, we see that in the one with the high cancer rate, 31.5 per cent of the inhabitants were over forty as contrasted with 19.6 per cent in the province with the low cancer rate; also that 13.3 per cent were over sixty in the former as compared with 4 per cent over sixty in the latter. While these percentages are based upon the 1921 census, and do not actually represent the percentages in 1928, nevertheless they indicate the tendency for a population with a high percentage of old people to show a much higher cancer rate than a population made up largely of pioneer families, in which the average age is much lower. Method of Colculatiiu; Cancer Rates: It is because the writer felt that these differences in age composition of the population in different provinces explained the differences in the cancer rate to a large degree, that the statistics for Canada for the years 1901 and 1921 have been considered and the cancer rates for different age groups of the population determined. Although cancer statistics are available for as late as 1929, the proportion of the population in different age groups is estimated only in the census years; hence the latest data on hand giving both age grouping and cancer statistics, are those for The population was divided for statistical purposes into three groups: (a) those under forty, in which cancer is relatively unimportant; (b) those between forty and sixty, in which there becomes noticeable a sudden upward sweep of the percentage of cancer cases; (c) a third group including those of sixty and over, in which cancer is even more important as a cause of death than in the second group. The cancer rate was calculated separately for

3 IS INCREASE OF CANCER REAL OR APPARENT? 1195 these three groups on the basis of the number of cancer deaths in the group per 100,000 of population occurring in that group. This method should at once settle the argument as to whether there was an actual increase in the percentage of cancer cases within the cancer ages in the period studied, or whether it merely appeared that there was an increase because there were more people living to the cancer age. Thus, if there were 100,000 persons over sixty in Canada in 1901, and 500 of these had cancer, the rate for those over sixty would be 500 per 100,000 of population over sixty. If, due to the saving of numerous lives in infancy, there were 1,000,000 persons over 60 in 1921, and of these there were 5,000 with cancer, the cancer rate of those over sixty would be exactly the same, namely 500 per 100,000. The cancer rate for the entire population would have risen because the proportion of those over sixty would be higher in the later year. There would be no actual increase, however, in cancer in those over sixty, although there would be more cases. Age of Death from Cancer: One of the problems which arises is the following: Is it the fact that cancer is tending to occur at progressively younger ages that has led to the idea that it is increasing? To answer this the average age of death from cancer was computed from the census of 1901 and from the vital statistics of Since the age of death was not given except in age groups of from thirty-five to forty-four, forty-five to fifty-four, etc., in 1901, and forty to fifty and fifty to sixty in 1921, the averages are necessarily inaccurate. Thus for the 1901 census, half of the age group from thirty-five to forty-four, with an estimated average age of forty, and half of that from fifty-five to sixty-four, with an estimated average age of sixty, were added to the age group from forty-five to fifty-four, with an estimated average of fifty. The figure thus obtained was taken as the population between forty and sixty in In 1921 the grouping was from forty to forty-nine and from fifty to fifty-nine. The average age of these groups was taken as being at the midpoints, forty-five and fifty-five, again probably introducing a considerable error. Allowing for these errors, one could say that there was no apparent tendency for the age of death to be lower in 1921 than in As a matter of fact, it was 59 for 1901 and 61.7 for Thus the average age at which cancer claims its victims does not appear to be decreasing.

4 1196 MADGE THURLOW MACKLIN This might be true, however, and yet the percentage of cancer cases occurring at the earlier ages might be increasing, that is to say, the number of cases below sixty might be more numerous than formerly, without the average age shifting in the downward direction. For example, if there were in the population four persons with cancer dying at the ages of forty, sixty, eighty, and one-hundred, the average age of death would be seventy; and 25 per cent of the cancer population would be under sixty. Now if there were eight persons with cancer dying at the ages of 100, 100, 80, 80, 60, 50, 50 and 40, the average age of death would still be TABLE 1 Percentage of Cancer CB88B under Forty Percentage of Cancer C&IleIl between Forty and Sixty Percentage of Cancer CB8elI over Sixty Alberta Ll British Columbia Manitoba New Brunswick... "... " Nova Scotia Ontario Prince Edward Island Quebec 2, " Saakatohewan CANADA as a whole The figures Cor Alberta and Saskatchewan for 1901 were those of the Territories of which they were a part. 2 Quebec was not included in the registration area of 1921; hence vital statistics were not available for that province in that year. a The upper row of figures is based upon statistics from Canada plus Quebec; the lower row upon the registration area of 1921, hence directly comparable with the 1921 columns. seventy, but the percentage of cancer cases under sixty would have risen from 25 to Cancer would be actually increasing among the younger population, without any shift in the average age of death. This is seen not to be the case, however, as is shown in Table 1. Although the percentages for different provinces vary somewhat, it is evident that the percentage of total cancer deaths in the first group (below forty) is lower in every instance, with the exception of Alberta, in 1921 than it was in In the second group (forty to sixty), also, with the exception of British Columbia, there were fewer cases proportionately in 1921 than there were in When we come to the last group, we see that in every

5 IS INCREASE OF CANCER REAL OR APPARENT? 1197 instance there is a much increased percentage of cancer cases in those over sixty. This is in agreement with the probable rise in the average age of death from cancer, and the two combined point to the conclusion that, if cancer is increasing, it is not due to there being more cases in proportion among the younger population, and that on the average it is not claiming its victims at a relatively earlier age. Increase in Age of Population as a Factor: Table 2 shows the percentages of the population in the three age groups in 1901 and With only one exception, Quebec, was the percentage of the TABLE 2 Percentalle of P'1.ulatlOn un or Forty Percentage of Population between Forty and Sixty Percentage of Cancer Rate Population 'Pcr 100,000 over Sixty opulation Alberta , British Columbia Manitoba New Brunswick Nova Scotia Ontario Prince Edward Island Quebec not given Saskatchewan CANADA as a whole The cancer rates for Alberta. and Saskatchewan were those of the Territories in which they were included in the year Since the registration area of Canada for 1921 did not include Quebec, two sets of 1901 figures are given, the upper row for Canada including Quebec, the lower row for Canada minus Quebec. The latter figures are to be contrasted with those for population under forty higher in 1901 than in 1921, thus indicating that there is a shift of the population toward the higher age levels. This means either (a) that the birth rate is falling or (b) that those born are helped to live until they are past the age of forty at least, that being the upper level of the first group. The first is not true, for we find that the birth rate for Canada per 1000 of population was 12.7 in 1901 as contrasted with 21.9 in The death rate per 1,000 was 15 in 1901 and 10.6 in 1921, which means that we are constantly prolonging the lives of persons not only past infancy, but into the age levels at which they may develop cancer. But, as was asked earlier, is the actual percentage of this population over forty, and over sixty, which is developing cancer greater in 1921

6 1198 MADGE THURLOW MACKLIN than in While the cancer rate for the entire population is steadily increasing, is the cancer rate within the cancer ages increasing? For an answer to that question we must turn to Table 3, in which the cancer rates per 100,000 of the three different groups have been tabulated. By such a division into groups, we can determine whether the cancer rate increase has merely kept pace with the population increase in the higher age levels, or whether it has exceeded that increase. The first two columns show the number of cases of cancer in persons below forty, per 100,000 of the population TABLE 3 Cancer Rate of Popu- Cancer lation from Rate Forty of Popu- to Cancer Rate of Popu- lation under Forty, Sixty per 100,000 of lation over Sixty per per 100,000 of Those 100,000 of Those under Forty Those from Forty to Sixty over Sixty Alberta I... " British Columbia Manitoba... " Hi New Brunswick Nova. Scotia Ontario... '"... " Prince Edward Island '" Quebec Saskatchewan I CANADA as a whole I The figures for Alberta and Saskatchewan for 1901 were based on the cancer rates for the Territories of which they were a part. 2 Quebec was not included in the registration area of Canada in 1921, hence there are no cancer statistics available for this province in that year. 'The upper row of figures is based upon Canada plus Quebec; the lower upon the registration area. of 1921, which makes it comparable with the 1921 columns. under forty for 1901 and In some provinces there has been an increase, in some a decrease; the number of cases being so small in some instances as to make conclusions based upon the data unreliable. For the whole of Canada, however, the figures are little changed. There were in 1901, 287 persons dying of cancer under forty, or a rate of 7 per 100,000 of population under forty. In Canada, not including Quebec, the cancerrate under forty was 8 per 100,000. In 1921, there were 320 persons dying of cancer under forty, giving a rate of 6.8 per 100,000 of population under forty. (The 1921 figures are based upon the registration area of Canada for 1921; Alberta and Saskatchewan were assigned the cancer rates for 1901 of the Territories of which they were a part.)

7 IS INCREASE OF CANCER REAL OR APPARENT? 1199 In columns 3 and 4 and 5 and 6, however, we see a very different condition. In columns 3 and 4 we find in every instance, with the exception of Prince Edward Island, a great increase in the 1921 column as compared with Thus, in Saskatchewan the rate increased for that section of the population between the ages of forty and sixty from 56.8 to 114. For all Canada it rose from 90.8 to For the registration area of 1921 it rose from 115 to In the section of the population over sixty we find an even more striking rise in the cancer rate. In Alberta it climbed from 202 per 100,000 in 1901 to 528 in For all Canada the rate TABLE 4 Number of Deaths in 1921 to Every 100 Deaths from Cancer in 1901 Under Forty From Forty to Sixty Over Sixty Alberta I... " British Columbia Manitoba New Brunswick 'i Nova Scotia Ontario Prince Edward Island Saskatchewan CANADA ae a whole The figures for Alberta and Saskatchewan for 1901 were those of the Territories of which they were a part. 2 Quebec W:l.S not included in the registration area of 1921, hence there were no cancer statistics available for Quebec for that year. The upper row of figures includes Quebec, the lower row compares the same two areas in 1901 and rose from 323 (for the registration area of 1921, from 336) to 578. This answers the question as to whether the rate of cancer increase has merely kept pace with the advancing age of the population or whether it is accelerating at a faster pace. There can be no doubt that cancer is increasing at a rate that is far in excess of the average increase in the percentage of population which is reaching the cancer age. In Table 4 are set forth the proportionate values of the cancer rates for 1921 as contrasted with the cancer rates for Thus we see that in 1921 Saskatchewan had just twice as many in proportion die of cancer between the ages of forty and sixty as had died in In Alberta two and three fifths as many in proportion to the population over sixty died over the age of sixty in 1921 as died in Those provinces which had a relatively high percentage of persons under forty in 1901 were, of course, the ones showing the highest rates of cancer increase in 1921.

8 1200 MADGE THURLOW MACKLIN It is of interest that when the cancer rates are thus computed, not upon the entire population but upon the portion of the population that is liable to cancer, Prince Edward Island, which in 1921 had the third highest cancer rate of any of the provinces based upon the entire population, had next to the lowest cancer rate for both the group between forty and sixty and that over sixty. Thus, there are fewer old persons with cancer in Prince Edward Island in proportion to the total number of old people than anywhere else in Canada, with the exception of Saskatchewan; despite the fact that this little province has such a high cancer rate when based upon its entire population. Manitoba, which had the third lowest cancer rate of all the provinces in 1921, based upon the entire population (Table 2, column 8) had by far the highest cancer rate for both the group between forty and sixty and that over sixty, when the cancer rate was computed upon the sections of the population of those ages (Table 3, columns 4 and 6). Such a condition shows the value of computing the cancer rates, not upon the basis of 100,000 of the entire population, but upon the portion of the population in which the cancerous group falls. Diagnosis as a Factor: We have shown, then, that cancer is increasing, and that this increase cannot be explained away by the statement that more persons are living to the cancer age, although that accounts for some of the increase, when cancer rates are based, as they usually are, upon the entire population. Is better diagnosis at the basis of the apparent increase? Let us study cancer of the lip, which, because of its appearance on the surface of the body in a most conspicuous place, is far less apt to go undiagnosed than cancer of the stomach or liver. What are the facts concerning it? In 1901 the death rate from cancer of the lip was 0.9 per 100,000 of the population. This had risen to 2.5 in 1921, a value almost three times as high. Dividing these cases into the three groups which we have used for all cancer, we find that the deaths between the ages of forty and sixty were 1.9 per 100,000 of the population between those ages in This value had increased to 2.5 in In the age group over sixty, the death rate per 100,000 from cancer of the lip was 7 in 1901, and had risen to 22 in Better diagnosis, therefore, although it undoubtedly is a large factor in causing the cancer rate to appear higher as the years go by, cannot be the sole explanation, since a cancer that could scarcely go undiagnosed even by the laity has shown such a tremendous increase in incidence.

9 IS INCREASE OF CANCER REAL OR APPARENT? 1201 Moreover, if better diagnosis or more accurate vital statistics were responsible, either wholly or partially, for the increased cancer rate, even when computed for the separate age groups as has been done in Table 3, we should expect to find that the cancer rate in all three groups had been raised. If the physician is better able to diagnose cancer at sixty, or records it more accurately, then he is able, also, to recognize cancer under forty more easily, and to record it more accurately. Therefore, we should expect to find increases in the age group under forty proportionate to those in the age groups between forty and sixty and over sixty. A glance at Table 4 shows us that such was not the case. In column 1, it is seen that in the Prairie Provinces there was a very great increase in the cancer rate under forty, which can probably be attributed directly to increased medical facilities. The rate in British Columbia was slightly higher than in 1901, there having been 105 deaths from cancer in this age group to every 100 deaths in In all the eastern provinces, however, the rate is materially lower in 1921 than in 1901, with the exception of New Brunswick, in which it is exactly the same. In Nova Scotia, in the age group under forty, there were in 1921 only 54 deaths from cancer to every 100 in Taking the rates for all Canada, there were only 97 deaths in this group from cancer in 1921 to every 100 in 1901, and for the registration area of 1921, only 85 deaths in 1921to every 100 in Thus, better diagnosis and more accurate statistics, which would be very apt to affect equally the cancer rate in all three groups, did not uniformly raise the cancer rate in the group under forty. This affords us an index as to the part played by better diagnosis and more accurate statistics in the other two groups. It seems fair to state that they undoubtedly playa rele, but that it is not a major role, inasmuch as they did not increase the cancer rate in the third group of the population, which is under forty. What then is at the basis of the increased cancer rate within the cancer ages? Reason for Increase in Cancer: The reason that cancer is increasing at such an alarming pace, both actually and relatively, is quite obvious. If we go back to the records of 1901, and determine the death rate for the age group between forty and sixty, from all causes which we might expect to be altered with increasing medical knowledge, better sanitation, more surgical skill, etc., we see that there were 621 persons dying of infectious diseases, of appendicitis, as a result of hernia operations, of childbirth, of accidents, and of a 06

10 1202 MADGE THURLOW MACKLIN group of undiagnosed diseases and "senility." In 1921, due to improved sanitation, there was less typhoid; due to better health conditions, there was less tuberculosis; due to better surgical skill, fewer persons died as a result of operations, etc. Due to better diagnosis, many of the cases which might have been labelled as senility or due to no specific cause, were placed in more accurate classifications, some of them no doubt being diagnosed as cancer. Hence for this great group of causes there were in 1921 but 374 deaths per 100,000 of the population from forty to sixty, a saving of 247 per 100,000 of lives over In the age group over sixty, there were, in 1901, 3103 per 100,000 dying of these preventable causes, while in 1921 the figure was Thus there were saved 1280 lives for every 100,000 persons. Of the 247 saved from forty to sixty, some may have been saved to live over into the next higher age group, or they may have been spared dying of pneumonia or smallpox or childbirth, only to succumb, before they were sixty, to cancer. Of the 1280 saved in the group over sixty, some may have been spared to live longer, but all must ultimately be accounted for among the deaths in this group. Since they do not die of infectious diseases or accidents, they succumb to those diseases which we may term constitutional in nature. Not only does preventive medicine bring more people to the cancer age, but it keeps them from dying of preventable causes after they get there, so that it is inevitable that the death rate from some few diseases, not preventable at present, will mount. The cancer rate might justifiably be used as an index of the state of preventive medicine and sanitation in a country. Those with good public health organizations have a high cancer rate; those with a low cancerrate show poorpublic health facilities. Those diseases which are dependent upon some inherited defect, and which, therefore, will not be influenced by advanced surgical technic or better sanitation, or by the ordinary preventive methods employed, will naturally be the ones which show the increase. We would, therefore, expect diabetes and many types of heart disease to show an increased death rate. Diabetes, to be sure, is by no means so exclusively a disease of old age as is cancer, and many of the heart diseases which are dependent upon a constitutional fault, such as congenital heart defects, cause death before the age of forty. Nevertheless, we find that diabetes caused among the entire population 140 deaths in 1921 as compared with 100 in If we consider the two age groups of forty to sixty and over sixty,

11 IS INCREASE OF CANCER REAL OR APPARENT? 1203 as we did for cancer, we find that in the former group there were 134 deaths from diabetes in 1921 to every 100 deaths in 1901; in the group over sixty there were 148 deaths in 1921 to every 100 in Thus the prevention of death from infectious diseases has raised the death rate from diabetes. When we turn to heart lesions, it becomes somewhat harder to separate those due to an inherited basis from those due to previous infection, for in the vital statistics many of these conditions are listed under a general heading. Although deaths from heart conditions were fewer for the age group from forty to sixty in 1921 than they were in 1901, in the group over sixty there were 161 deaths in 1921 to every 100 in To present this matter in a different way: if the increase in cancer rate were dependent merely upon the saving of lives in infancy and youth so that they reached the cancer age, we could state exactly how many persons over sixty and between forty and sixty should have died in 1921 as contrasted with Exclusive of Quebec, there were 733 persons between forty and sixty dying of cancer in Canada in Had the same proportion died in 1921, the number would have been Actually it was There were 982 persons over sixty dying of cancer in If the same proportion had died in 1921, the number of deaths from cancer in this group would have been Actually the number was Were the increase in cancer rates due merely to prolongation of lives into the cancer ages, the cancer rate for the registration areain 1921 would have been 53.7 in place of 75. This is readily understood when we look at Table 2 and see that there was only one per cent more of the population in the groups over forty in 1921 than in 1901, the area being considered corresponding to the registration area of 1921 in both cases. Thus it has been the saving of lives after they have reached the cancer age that has been perhaps the greatest factor in the increase of deaths due to cancer, unless we postulate that those who were saved in childhood were more susceptible to cancer than the general population. We may visualize mankind as walking over a bridge which spans the river of death. Along its length and width are many trap-doors, through which the unwary traveler may drop into the dark-flowing stream beneath. As the trap-door of infant mortality opens far less frequently than it did before; as the trap-door of yellow fever is practically shut; as the trap-doors for malaria and typhoid and smallpox open but once where they formerly opened a

12 1204 MADGE THURLOW MACKLIN score of times, we find that the troop of people is not nearly so thinned out by the time the middle of the bridge is reached as in years gone by. Even in the last half of the bridge, the trap-doors that once sprang open with alacrity, now move rustily on their hinges, and the throng which formerly dropped from sight through their hungry mouths now moves over them almost unaware of their existence. But it is a law imposed upon all those who start upon that journey, that they shall never reach the far side. At some time they must leave the crowd and sink into the river. Some of them almost finish the span, and the further they go, the fewer are the trap-doors to betray their footsteps; but at the end, although they are few, they are wide and long, and those who avoided the pitfalls farther back, now drop from sight through fewer doors, that yawn more widely. Much has been done to lengthen the time which anyone may spend upon the bridge of life. In 1901 the average age of death in Canada was 31; in 1921 it was If we exclude all those dying under 5, the average age of death was 49.5 in 1901, and 53.2 in In 1901the death rate per 1,000 was 15; in 1921it was We must all die of something, and it is inevitable, as we eliminate one cause of death after another, that we increase the death rate from the causes that remain, for while we may increase the length of life, we do not decrease the certainty of death. SUMMARY Cancer is increasing, and it is increasing particularly in the age group over sixty. The reason for its increase is not that it is occurring at progressively younger ages, or attacking larger percentages of the younger population. Despite its increase, deaths are fewer from all causes now than they were. We have won more ground from the ravages of infectious disease than we have lost to those disorders which are dependent upon inherent qualities in the chemical and physical makeup of the individuals. Cancer is increasing because, by preventive methods, there has been created a larger population to grow old; and having grown old, they are kept from dying of those ills from which they formerly suffered. With each increase in the warfare against preventable diseases, there will be an increase in the ravages from cancer, for with each victory there is created a greater available population to die from that disease. These conclusions are based upon the statistics of Canada.

13 IS INCREASE OF CANCER REAL OR APPARENT? 1205 There is strong ground for believing that a similar analysis of the statistics of any other country would lead to the same conclusions. It is true that there may be racial differences in immunity to cancer, but the conclusion here reached will probably prove universal, namely that excellent public health measures and high cancer rates are inseparable, at least for the present. Those who point to the low cancer rates existing among primitive peoples, and who state that cancer is a disease of modern civilization, neglect to call attention to the fact that preventive medicine is itself a triumph of modern civilization.. NOTE: The sources upon which this paper is based are Census of Canada, vol. 4,1901; Sixth Census of Canada 1921, vol. 2; Vital Statistics for No data for the year 1911 are included, since vital statistics for that year were not published.