be differentiated from another type of acute joint pain that may develop during a flight or under water. With reduction of barometric pressure, nitrogen dissolved in the body fluid and fat compartments evolves as gas bubbles. These bubbles may produce pain, especially around the joints. These pains are generally referred to as the "bends", one of the clinical manifestations of decompression disease. In pilots the bends usually occur at altitudes above 7000 metres (barometric pressure, 380 mm Hg), but scuba diving in the previous 24 hours may lower this threshold to 2400 metres (barometric pressure, 565 mm Hg). Exercise, obesity, old age and decrease in environmental temperature may lower this threshold even further. An increased awareness among physicians is needed to identify underlying hemoglobinopathies in individuals with acute joint pain at excessive altitudes or depths. BERNARD A. KATS, MD Associate professor of medicine Michigan State University East Lansing, Ml
References 1. KATS BA: The black pilot and sickle cell disease. Flying Physician 17: 1, 1974 2. Idem: Risk in sickle cell trait. Ann intern Med 79: 289, 1973 3. SCHUMACHER HR, ANDREWS R, MCLAUGHLIN
G: Arthropathy in sickle cell disease. Ann intern Med 78: 203, 1973 4. KATS BA: Arthropathy in sickle cell disease. Air I Med Sci 5: 179, 1976
Metabolism of ethanol in different racial groups To tke editor: During the last few years there have been several reports on the rates of metabolism of ethanol, and in some instances acetaldehyde, in different racial groups.1'2 Two such reports have appeared in the Journal; that of Fenna and associates (one of whom was myself) in 1971 (Can Med Assoc J 105: 472) and that of Reed and colleagues in 1976 (Can Med Assoc J 115: 851). Fenna and associates reported that northern woodland Indians metabolized ethanol significantly more slowly than controls - male Caucasian hospital personnel and students. Bennion and Li' reported no difference in the rates of ethanol metabolism in a group of Indians from the Phoenix area of Arizona and a control group of Caucasian subjects. Reed and colleagues reported that their group of Ojibwa metabolized ethanol more rapidly than did their Caucasian and Chinese groups, though they did note that the Ojibwa were much heavier drinkers. Strict comparison of these studies is not possible but several aspects are worth noting: 1. Route of ethanol administration. Oral administration produces certain ir-
regularities in absorption and had to be considered by Reed and colleagues. The study of Fenna and associates is the only one in which the ethanol was given intravenously at a controlled rate. 2. Interval for ethanol equilibrium. The study of Fenna and associates is the only one in which a specific time was allowed for the establishment of ethanol equilibrium in the various body compartments prior to testing. This is important when the subjects differ in body leanness. As Reed and colleagues pointed out, ethanol distribution is confined essentially to body water; thus, when ethanol is administered on a weight basis, obese subjects have a decreased fraction of weight that is relevant to ethanol metabolism. This may at least partially account for the relatively rapid metabolic rate of ethanol in their lean Chinese group. 3. Differences in habitual consumption of alcohol. Greater attention should be paid to this factor. The Amerind group studied by Reed and colleagues is known for its heavy consumption of alcohol. Even excluding the data of their heavy drinkers as unreliable, the consumption of alcohol in their Ojibwa subjects exceeded that of their other racial groups by 50 to 300% - and double that if no questionable data were omitted. Fenna and associates found habitual consumption of alcohol to be important in their study, reporting a significant difference in the rate of ethanol metabolism among their groups of Indians classed as light and heavy drinkers. 4. Apparent discrepancy in rates of ethanol metabolism in various groups. This too requires closer study. Compared with the rate in control groups, the metabolic rate in Amerinds was found to be slower by Fenna and associates, the same by Bennion and Li' and more rapid by Reed and colleagues. As Reed and colleagues pointed out, Amerinds are not a homogeneous group but a nation made up of many subgroups and cultures. The northern woodland Indians studied by Fenna and associates traditionally have been almost exclusively carnivorous, while the Indians studied by Bennion and Li' have a high carbohydrate intake, are obese and have a high prevalence of diabetes mellitus, a condition rare among northern woodland Indians. In conclusion, studies comparing the metabolic rates and organic effects of alcohol in various racial groups are relatively new. They have important political and social as well as biologic implications. To. date they have not been comparable and are fragmentary and preliminary. Better organized studies of larger scale are required. This country, with its heterogeneous racial background, would be ideal for a high-
476 CMA JOURNAL/MARCH 5, 1977/VOL. 116
iy sophisticated multicentre of this most important issue. J.A.L. GILBERT, MD Royal Alexandra Hospital Edmonton, Alta. 0. SCHAEFER, MD Charles Camseil Hospital Edmonton, Alta.
To the editor: We agree with Drs. Gilbert and Schaefer about the desirability of further, careful studies on alcohol metabolism and response in different racial groups. We also agree that all published studies on rates of ethanol metabolism, including ours and that of Fenna and associates, have had various problems in methodology; we discussed some of these at length in our paper. What is important is that these problems are being identified and that, when they cannot be avoided, one can sometimes estimate and correct for their effects. The effect of habitual consumption of alcohol on the rate of ethanol metabolism is an example of a problem that cannot be avoided but whose consequences can usefully be corrected for. Dr. Gilbert and his colleagues in their 1971 study reported that the rate of ethanol metabolism among their Indian subjects was 36% higher in heavy drinkers than in light drinkers. In our 1976 paper we calculated, with data on the Arizona Indians studied by Bennion and Li,a that heavy drinkers metabolize ethanol 19 ± 7% (mean ± standard error) more rapidly than light drinkers. Since the Ojibwa subjects in our study metabolized ethanol 76 ± 16% more rapidly than the Caucasian subjects (and correcting for proportion of body fat would increase this difference), we believe that we can claim a real difference in rate, notwithstanding the greater habitual consumption of alcohol by the Ojibwa. We invite interested readers to read the papers referred to. Comparison of alcohol response, metabolic and physiologic, in different races is attracting increasing attention. An additional published study, on Tarahumara Indians in Mexico, has shown that Indians appear to metabolize alcohol faster than Caucasians,5 and there are a number of unpublished studies. In a few years we may begin to have the comparative data we all would like to see. T.E. REr.n, PH D HAROLD KALANT, MD, PH D Departments of zoology and pharmacology University of Toronto Toronto, Ont.
References 1. EwING JA, RousE BA, PELLIZZARI ED: Alcohol sensitivity and ethnic background. din J Psychiatry 131: 206, 1974 2. BENNION IJ, Li T-K: Alcohol metabolism in American Indians and whites. N Engi I Med 294: 9, 1976 3. zEINER AR, PARaDES A, COWDEN L: Physiologic responses to ethanol among the Tarahumara Indians. Ann NY Acad Sci 273: 151, 1976
References 1. KATS BA: The black pilot and sickle cell disease. Flying Physician 17: 1, 1974 2. Idem: Risk in sickle cell trait. Ann intern Med 79: 289, 1973 3. SCHUMACHER HR, ANDREWS R, MCLAUGHLIN
G: Arthropathy in sickle cell disease. Ann intern Med 78: 203, 1973 4. KATS BA: Arthropathy in sickle cell disease. Air I Med Sci 5: 179, 1976
Metabolism of ethanol in different racial groups To tke editor: During the last few years there have been several reports on the rates of metabolism of ethanol, and in some instances acetaldehyde, in different racial groups.1'2 Two such reports have appeared in the Journal; that of Fenna and associates (one of whom was myself) in 1971 (Can Med Assoc J 105: 472) and that of Reed and colleagues in 1976 (Can Med Assoc J 115: 851). Fenna and associates reported that northern woodland Indians metabolized ethanol significantly more slowly than controls - male Caucasian hospital personnel and students. Bennion and Li' reported no difference in the rates of ethanol metabolism in a group of Indians from the Phoenix area of Arizona and a control group of Caucasian subjects. Reed and colleagues reported that their group of Ojibwa metabolized ethanol more rapidly than did their Caucasian and Chinese groups, though they did note that the Ojibwa were much heavier drinkers. Strict comparison of these studies is not possible but several aspects are worth noting: 1. Route of ethanol administration. Oral administration produces certain ir-
regularities in absorption and had to be considered by Reed and colleagues. The study of Fenna and associates is the only one in which the ethanol was given intravenously at a controlled rate. 2. Interval for ethanol equilibrium. The study of Fenna and associates is the only one in which a specific time was allowed for the establishment of ethanol equilibrium in the various body compartments prior to testing. This is important when the subjects differ in body leanness. As Reed and colleagues pointed out, ethanol distribution is confined essentially to body water; thus, when ethanol is administered on a weight basis, obese subjects have a decreased fraction of weight that is relevant to ethanol metabolism. This may at least partially account for the relatively rapid metabolic rate of ethanol in their lean Chinese group. 3. Differences in habitual consumption of alcohol. Greater attention should be paid to this factor. The Amerind group studied by Reed and colleagues is known for its heavy consumption of alcohol. Even excluding the data of their heavy drinkers as unreliable, the consumption of alcohol in their Ojibwa subjects exceeded that of their other racial groups by 50 to 300% - and double that if no questionable data were omitted. Fenna and associates found habitual consumption of alcohol to be important in their study, reporting a significant difference in the rate of ethanol metabolism among their groups of Indians classed as light and heavy drinkers. 4. Apparent discrepancy in rates of ethanol metabolism in various groups. This too requires closer study. Compared with the rate in control groups, the metabolic rate in Amerinds was found to be slower by Fenna and associates, the same by Bennion and Li' and more rapid by Reed and colleagues. As Reed and colleagues pointed out, Amerinds are not a homogeneous group but a nation made up of many subgroups and cultures. The northern woodland Indians studied by Fenna and associates traditionally have been almost exclusively carnivorous, while the Indians studied by Bennion and Li' have a high carbohydrate intake, are obese and have a high prevalence of diabetes mellitus, a condition rare among northern woodland Indians. In conclusion, studies comparing the metabolic rates and organic effects of alcohol in various racial groups are relatively new. They have important political and social as well as biologic implications. To. date they have not been comparable and are fragmentary and preliminary. Better organized studies of larger scale are required. This country, with its heterogeneous racial background, would be ideal for a high-
476 CMA JOURNAL/MARCH 5, 1977/VOL. 116
iy sophisticated multicentre of this most important issue. J.A.L. GILBERT, MD Royal Alexandra Hospital Edmonton, Alta. 0. SCHAEFER, MD Charles Camseil Hospital Edmonton, Alta.
To the editor: We agree with Drs. Gilbert and Schaefer about the desirability of further, careful studies on alcohol metabolism and response in different racial groups. We also agree that all published studies on rates of ethanol metabolism, including ours and that of Fenna and associates, have had various problems in methodology; we discussed some of these at length in our paper. What is important is that these problems are being identified and that, when they cannot be avoided, one can sometimes estimate and correct for their effects. The effect of habitual consumption of alcohol on the rate of ethanol metabolism is an example of a problem that cannot be avoided but whose consequences can usefully be corrected for. Dr. Gilbert and his colleagues in their 1971 study reported that the rate of ethanol metabolism among their Indian subjects was 36% higher in heavy drinkers than in light drinkers. In our 1976 paper we calculated, with data on the Arizona Indians studied by Bennion and Li,a that heavy drinkers metabolize ethanol 19 ± 7% (mean ± standard error) more rapidly than light drinkers. Since the Ojibwa subjects in our study metabolized ethanol 76 ± 16% more rapidly than the Caucasian subjects (and correcting for proportion of body fat would increase this difference), we believe that we can claim a real difference in rate, notwithstanding the greater habitual consumption of alcohol by the Ojibwa. We invite interested readers to read the papers referred to. Comparison of alcohol response, metabolic and physiologic, in different races is attracting increasing attention. An additional published study, on Tarahumara Indians in Mexico, has shown that Indians appear to metabolize alcohol faster than Caucasians,5 and there are a number of unpublished studies. In a few years we may begin to have the comparative data we all would like to see. T.E. REr.n, PH D HAROLD KALANT, MD, PH D Departments of zoology and pharmacology University of Toronto Toronto, Ont.
References 1. EwING JA, RousE BA, PELLIZZARI ED: Alcohol sensitivity and ethnic background. din J Psychiatry 131: 206, 1974 2. BENNION IJ, Li T-K: Alcohol metabolism in American Indians and whites. N Engi I Med 294: 9, 1976 3. zEINER AR, PARaDES A, COWDEN L: Physiologic responses to ethanol among the Tarahumara Indians. Ann NY Acad Sci 273: 151, 1976
