Raymond Pearl on Alcohol and Longevity
Whenever a young research fellow would bring up a hot topical issue to Francisco Grande, that grand continental gentleman of the Minnesota Laboratory of Physiological Hygiene, the sage would remark, almost without fail, something of this order: “Oh yes, Claude Bernard found that in 1864,” or “So- and-so had that idea in 1752.” When one queried “Paco,” there was “nothing new under the sun.”
So, if one were to ask him what he thought of the J-shaped relation recently noted between alcohol consumption and mortality, in which those drinking modest amounts of alcohol had a lower death rate and greater life expectancy than that of abstainers, he would undoubtedly have raised the name of Raymond Pearl and the date, 1926, then thrown in an aphorism or two from Hippocrates on the healthful value of wine drinking in moderation!
Pearl, indeed, was the first to propose and confirm, at the height of the U.S. prohibition era, his a priori hypothesis that moderate alcohol drinking was not a threat to survival. He was the first to study it rigorously in large data sets and with appropriate consideration of confounders and other influences on causal inference. First, he provided a knowledgeable account of natural selection, concluding that “duration of life is the most simple and direct measure possible of the survival value of an individual. . .This attribute of the individual, his duration of life, is, then, clearly a character of fundamental biological significance”(7,8).
With this concept he explains how much of the research energy of his laboratory was devoted to the study of life expectancy, and how he designs and studies the factors that affect the duration of life, recognizing the infeasibility of most human experiments. “Rather one would construct life tables for different groups of individuals, each of which had received a diet throughout life different in some one item, or at most in a few particulars, from those given to the other groups”(9). For alcohol, he states: “the real interest is to find out what effect alcohol has upon life duration when taken in amounts much smaller than those acutely poisonous, and in fact, apparently harmless” (9).
At this early time he already asks the question only recently addressed in modern epidemiology about the influence of patterns of drinking: “In the wine and beer drinking countries of Europe alcohol is extensively used as a normal and useful part of the diet.” Thus, he considered alcohol a food by definition, because completely oxidized and available for useful work, “a food that can replace equivalent amounts of fats and carbohydrates and spare protein in the same way that fats and carbohydrates can” (10). He already recognized that millions of people in Europe actually obtained a larger proportion of their total energy from alcohol than they did from protein. In other words, is the pattern of drinking important in determining its health effects. In a whole series of references and personal experiments he establishes to his satisfaction that ethyl alcohol can be administered many living organisms in ways that do not harmfully affect their duration of life.
These findings were so different from the commonly held views in the 1920s about the negative biologic effects of alcohol as to excite curiosity to investigate the problem in humans, in which all might profit from Pearl’s humility in describing his epidemiologic studies: “It is the purpose of this book to set forth the results of the analysis of a mass of unique statistical data regarding the influence of alcohol upon longevity. While these records do not reach the highest ideal which one might theoretically set for material with which to investigate the problem, it is nevertheless true that they do give with sufficient accuracy certain important information which has hitherto been lacking” (29).
Because one must fall back on statistical approaches to study the issue rather than by experiment, he defines the conditions for such statistical study to include recording the place and date of birth of each individual and their socio-economic and racial status. He then recruited from the Family History Study at Johns Hopkins about characteristics of individuals developing tuberculosis, collecting detailed information on the pattern of drinking and smoking, the kind and amount of alcoholic beverage used, the frequency of use, the pattern of drinking with and separately from meals, and changes in alcohol use throughout life. Then he confirmed these responses by interviews with relatives.
His basic classification was into abstainers, moderate drinkers who did not get intoxicated, and those who drank to drunkenness regularly, all according to age social and ethnic status, after which subjects were followed to assign the date and cause of death. All data were collected in Baltimore prior to Prohibition. The total experience involved 5,248 individuals, 1800 of which were abstainers, 1400 moderate drinkers, and 700 heavy drinkers. [ed. He described his select population with the same sorts of descriptors, “normal active people,” as Ancel Keys used about the select business and professional cohort he recruited in the 1940s.]
In the end, Pearl concluded that heavy drinking had a deleterious effect on mortality and longevity, but, with “an equivalent precision,” he claimed there was no such effect of moderate drinking. “Instead the mortality among moderate drinkers is generally the same as among total abstainers, or less, and the average longevity is greater” (141). “The expectation of life of the moderate drinkers, whether male or female, is higher at all ages than the expectation of life of abstainers. Certainly [there is] no evidence that the expectation of life from age 30 on is in any degree impaired by the moderate consumption of alcoholic beverages, as defined in this book” (115).
Though heavy-drinking men had a life expectancy much less than others, there were insufficient data on heavy-drinking women and there was very little association with mortality after age 70. Having demonstrated that in this group moderate drinking did not impair life expectancy or increase the mortality rate, Pearl examined categories of drinking habits, concluding that opinion derived from propaganda against alcohol presented no original observations and that early experience of life insurance companies confirmed the more modern data that heavy drinking is deleterious. His reviews of data from United Kingdom special insured groups concludes that insurance data provide no information on lifetime alcohol habits and are biased from the outset because insurance companies discriminate against alcoholism.
He comments on all such early evidence as follows: “The trouble with all this indirect evidence on alcohol and mortality is that from its inherent character it cannot possibly prove anything, no matter how much it may be multiplied in amount. It merely suggests or implies what may be so. But, in plain fact, it is only suggestive, not probative, and quite certainly in some cases suggests a wrong rather than a right conclusion” (143). And he finally dismisses the opinion of physicians: “The physicians’ estimates of the percentage of deaths due to alcohol, from any particular cause, or from all causes, are simply a rough measure of medical ignorance of the effects of alcohol upon the living organism” (149).
Addressing ecologic analyses of the consumption of alcohol per head of population with the death rate, he shows that in younger ages mortality is lower according to the amount of alcohol per capita but concludes: “probably all such studies as this can have but little scientific value in the elucidation of the problem of the influence of alcohol on mortality. They leave out of consideration so many important factors as to make their results of no more than suggestive value at best” (153).
In Chapter 7 on interpretation of the evidence he sums up social attitudes comparing teetotalers and drinkers: “On the one hand then, we have the combination of drink and the devil, and on the other hand of teetotalism and the crank, with the result that statistical measurement of the effect of alcohol upon mortality seems to be impossible” (172).
In his own search to dissect the truth from such statistical study, he turned to brothers and sisters exposed to different doses of alcohol that went back to a comparison of brother pairs, with data among male abstainers who had 113 moderate-drinking brothers with highly accurate records on their health and alcohol consumption. Though the findings are irregular because of the small sample size, “what evidence they do afford favors the view that the moderate drinking has not adversely affected duration of life” (176). Assuming that these pairs are more nearly alike in genetic constitution than random pairs, he feels that his small study “confirms the conclusion that moderate drinking does not sensibly shorten the duration of life” (176).
As to mechanisms, Pearl reviews the studies of acute effects of alcohol on blood pressure and heart rate and sums up the evidence as follows: “In the physiological, general biological and clinical studies which have been made on alcohol, when the dosage is of the order of that involved in moderate drinking by human beings, there are extremely few results recorded which can be regarded as biologically deleterious. There are many results, well established by critical experimentation and observation, that indicate that small amounts of alcohol are beneficial in some biological processes” (184).
Moral convictions and matters of taste
In the final chapter Pearl summarizes and concedes that the superiority of mortality in moderate drinkers is not highly significant statistically, “but it certainly gives no support to the almost universal belief that alcohol always shortens life, even in moderate quantities”(226). Anyone disagreeing with his conclusion must assume the burden of proof: “On the principle of Occam’s razor the most probable explanation seems to me to be the simple one that the moderate consumption of alcoholic beverages has no deleterious biological effects.” “..in the considerable sample of the working class population of Baltimore here studied, moderate drinkers did live, on the average, just as long as total abstainers, in truth a little longer” “These then are the results of this investigation” (228).
“Given this situation mankind divides itself promptly into two moieties, on the basis really of taste. Those in the one group feel it their most sacred duty to prevent the weak brother from getting the chance to liquidate his weakness in terms of the particular deleterious agent, at least. The other group feels that it is neither right nor decent to deprive the great bulk of normal humanity of a harmless source of pleasure in order that a small group of persons deficient in self control may theoretically be kept out of temptation. The difference between these two groups of honest and sincere human beings is, I repeat, at bottom a matter of taste, of general outlook on life”(228).
This then is the conclusion of Pearl’s book on alcohol and mortality, published in the face of and at the height of the moral and legal preponderance of the U.S. Prohibition Era (Henry Blackburn).
Pearl, Raymond. 1926 Alcohol and Longevity. New York: Alfred A. Knopf.