J Clh l+Idaakl
0895-4356/91 S3.00 + 0.00 Copyright 0 1991 Pergamon Press pk
Vol. 44, No. 11, pp. 1255-1261, 1991
Printedin GreatBritain. All rights reserved
PHYSICAL ACTIVITY, DIETARY HABITS AND ADENOMATOUS POLYPS OF THE SIGMOID COLON: A STUDY OF SELF-DEFENSE OFFICIALS IN JAPAN SUMINORI KoNo,‘*
KOICHI SHINCHI,~ NARIAKIIKEDA,’ FCJMIOYANAI~
and KOJI IMANISHI~ ‘Department of Public Health, National Defense Medical College, Tokorozawa, Saitama 359, Japan and %Af-Defense Forces Fukuoka Hospital, Kasuga-sbi, Fukuoka 816, Japan (Received in revisedform 27 February 1991)
Abstract-Physical activity and dietary habits were compared between 80 men with adenomatous polyps of the sigmoid colon and 1148 men with normal colonoscopy among male retiring self-defense officials. Physical activity as expressed in terms of time spent doing strenuous activities during leisure time was inversely related to the risk of adenomatous polyps. Controlling for rank, smoking, alcohol and body mass index (BMI), odds ratios for the categories of 0, l-59, 60-l 19 and 2 120 minutes per week were 1.0, 0.88, 0.70 and 0.44, respectively (trend p = 0.015). Among a limited range of foods and beverages, the consumption of rice, green tea and instant coffee tended to be associated with a decreased risk of adenomatous polyps. Although the associations observed with dietary habits still need to be substantiated, the findings on physical activity lend further evidence to the hypothesis that physical activity may be protective in the development of colon cancer. Colon polyps
Physical activity
Diet
INTRODUCTION
Colon cancer is one of the most common cancers in western countries, and mortality from this cancer in Japan has rapidly increased over the past decades, following the westernization of this country [I, 21. Diet has been a main focus in epidemiology of colon cancer, and it has been suggested that diets high in animal fat and low in fiber increase the risk of colon cancer although epidemiological evidence is not congruent [3]. Recently, the role of exercise in the etiology of colon cancer has drawn considerable interest. Several epidemiological studies have reported that low physical activity is associated with an increased risk of colon cancer [4-lo], *All correspondence should be addressed to: Suminori Kono, M.D., Department of Public Health, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359, Japan. CE U/II--I
Japanese men
while other studies failed to find such an association [II, 121. Adenomatous polyps are a well-established precursor lesion of adenocarcinoma of the large bowel [13, 141. In epidemiological aspects, the use of this precursor lesion as an end-point preceding the occurrence of colon cancer has methodological virtues due to the reduction in the time period between exposure and outcome. Surprisingly, however, there have been only a few epidemiological studies of colon polyps regarding diet and physical activity. To our knowledge, two case-control studies [15, 161 and one autopsy study [17] have so far directly examined the relation between diet and adenomatous polyps of the large bowel. The latter study was based on prospective data in a cohort of Japanese men in Hawaii [lo], and this study examined the relationship with physical activity but observed no association [17]. In a
1255
KONOet al. SUMINOR~
1256
population of middle-aged Japanese men, we examined the risk of adenomatous polyps of the sigmoid colon in relation to physical activity and dietary habits. MATERIALS
AND MJZTHODS
Subjects were male self-defense officials who received, between October 1986 and December 1988, a retirement health examination at the Self-Defense Forces (SDF) Fukuoka Hospital, which is part of a nationwide program offering free comprehensive medical examinations for those retiring from the SDF. The age at retirement is mostly early 5Os, and the health examination is done within the year before retirement. In October 1986, we included a lifestyle survey in the SDF Fukuoka Hospital program and started systematic collection of individuals’ medical data. The health examination was done during a 5-day admission and included colonoscopy among others. The following information was extracted from the medical records for data processing; height, body weight, systolic and diastolic blood pressures, blood group, serum biochemical data, results of 75 g oral glucose tolerance test, colonoscopy and ultrasonography of the biliary tract, current medication for selected diseases and past medical history. Details on the procedure and results of colonoscopy have been described elsewhere [ 181. In brief, routine colonoscopy was to examine the rectum and sigmoid colon, and more proximal sites were explored if the subjects tolerated physical discomfort. Colonoscopy with intubation of less than 40 cm was regarded as unsatisfactory, and polyps located at 1l-60 cm from the anus were arbitrarily defined as polyps of the sigmoid colon. In the series of 1460 men, 1348 men underwent satisfactory colonoscopy. With the exception of 6 men who had a history of colectomy or polypectomy of the large bowel, 154 men were found to have at least one polyp, and 1188 were free of pathological lesions; 88 men had histologically confirmed adenomatous polyps of the sigmoid colon. The present study excluded those having conditions which may iniIuence physical activity and dietary habits (chronic bowel disease, post-surgery or newly diagnosed cancer, history of apoplexy, history of myocardial infarction, other coronary heart disease on medication and known diabetes mellitus). Two cases of colon polyposis were also excluded, and the study subjects consisted of 80 cases of
adenomatous polyps of the sigmoid colon and 1148 controls with normal colonoscopy. Self-administered questionnaires were distributed on the first day of admission and collected on the second day with a supplementary interview for unaswered questions. The questionnaire queried smoking and drinking habits, physical activity, dietary habits and medical history. Assessment of smoking and drinking habits and their relation to adenomatous polyps have been published previously [18]. Assessment of physical activity Besides recreational activities, questions on physical activity asked about the average amount of time per day spent asleep, different ways of transport (walking, cycling and running), 5 different levels of activity at work (sedentary, standing, walking, light manual work and heavy manual work), housework and stair-climbing. Regarding recreational activities, frequency (closed-ended question) and duration (open-ended question) were queried for 21 listed activities, if any of them had been performed at least once per month throughout the past year. Any unlisted regular recreational activites were also inquired for. Individuals were further asked whether they had currently refrained from physical exercise due to health problems, and, if so, the period of refraining and health problems were specified. In order to choose an appropriate variable of physical activity in examining the relation with the risk of adenomatous polyps, various indices as to energy expenditure and the amount of time spent for selected activities were validated against serum HDL-cholesterol level, because physical activity is well known to increase it [19]. In accordance with the method used in the Five-City Project [20], activities were classified into 4 levels of intensity by referring to MET values (ratio of working metabolic rate/resting metabolic rate) in the published literature [20,21]. Examples of the intensity classification are given in Table 1. Sleep was coded as 1 MET, and the residual hours per day obtained by subtraction (24 hours minus those spent for reported activities) were regarded as being spent for light activities. Energy expenditure (kcal/kg/day) for selected activities was estimated on the basis of 1 MET = 1 k&/kg/day by summing the products of hours spent for each category of intensity and the corresponding MET score (light = 1.5, moderate = 4, hard = 6 and very hard = 10).
Physical Activity, Diet and Colon Polyps
1257
Table 1. Classification of the intensity of physical activities Example of activities METS value
Occupational
Recreational
Light
1.0-2.9
Desk work, janitorial work
Walking for pleasure, bowling, fishing
Moderate
3&5.0
Walking, housework
Cycling, dance, golf, pingpong, tennis (doubles)
Hard
5.1-6.9
Light manual work (carpentry, painting)
Jogging, tennis (singles), karate
Very hard
7.g
Heavy manual work (digging, carrying heavy load)
Running, football, swimming, body-buiklina. iudo
Intensity
Results shown in Table 2 were based on the analysis of 1316 men excluding those having the following conditions: hypertension on medication, known diabetes mellitus, post myocardial infarction, other coronary heart diseases on medication, thyroid disease, nephrosis/nephritis and any diseases under steroid therapy [19]. The amount of time spent for hard and very hard recreational activities was most strongly associated with serum HDL-cholesterol, and this simple index was used as a variable of physical activity in examining the association with adenomatous polyps. After adjustment for smoking, drinking and body mass index (BMI, body wt (kg)/height (m*)), mean concentrations of HDL-cholesterol for the categories of 0, l-59, 60-l 19 and 2 120 minutes per week were 51.5, 53.3, 54.2 and 56.9mg/dl, respectively.
raw vegetables, fruits, raw fish, soy saucecooked fish, broiled fish and meats, as an average over the past year. Preceded answers were used for consumption frequency, and the quantity was answered in terms of a conventional serving unit. The consumption of foods and beverages was categorized into three levels as shown in Table 3. Men drinking black tea were too few to justify the analysis. Reproducibility of dietary assessment was tested on 49 men who received the health examination in January 1989 with an interval of l-2 months, using a modified questionnaire which contained essentially the same dietary questions. Reproducibility as expressed by the intraclass correlation coefficient was generally good except for meat consumption.
Assessment of dietary habits
Logistic regression analysis was used to control for possible confounding effects of rank, smoking and alcohol consumption. Because obesity has been suggested as a potential confounder in the association between physical activity and colon cancer [22], BMI was also considered in the analysis on physical activity.
Dietary questions included frequency of consumption and amount consumed for five nonalcoholic beverages (brewed coffee, instant coffee, black tea, green tea and milk), rice and soy paste soup, and also the frequency of consumption regarding bread for breakfast, pickles,
Table 2. The associations
between serum HDL-cholesterol variables (n = 1316)
Activities taken into account source
Statistical analysis
Intensity
Energy expenditure (kcal/kg/day) Recreational M+H+V H+V Recreational and M+H+V occupational H+V Total? Amount of time spent (&z/week) Recreational M+H+V H+V
and various physical activity
Pearson’s correlation coefficient
Analysis of covariance*
0.118 0.134 0.100 0.076 0.097
15.96(0.0001) 24.27(0.0001) 9.71(0.002) 5.73(0.02) 9.52(0.002)
0.088 0.135
8.19(0.004) 26.OO(O.OOOi)
F-value (p-value)
Intensity: M = moderate, H = hard, V = very hard. *Independent variables were smoking (never, past and current: ~20 or 220 cigarettes/day), alcohol consumption (never, past and current: -z 30, 30-59 or 2 60 ml of alcohol/day), BMI (kg/m*) and a variable for physical activity. tIncluding sleep, all reported activities, and the residual activities obtained by subtraction.
SUM~NORI KONO et
1258
al.
Table 3. Consumption category of foods and beverages, and renroducibihtv of dietarv assessment Consumption category Food or beverage
Low
Intermediate
High
Intraclass correlation coefficient*
Rice Soy paste soup Bread for breakfast Pickles Raw vegetables Fruits Fish, combinedt Meats Brewed coffee Instant coffee Green tea Milk
< 3 bowls/day c 1 bowl/day
0895-4356/91 S3.00 + 0.00 Copyright 0 1991 Pergamon Press pk
Vol. 44, No. 11, pp. 1255-1261, 1991
Printedin GreatBritain. All rights reserved
PHYSICAL ACTIVITY, DIETARY HABITS AND ADENOMATOUS POLYPS OF THE SIGMOID COLON: A STUDY OF SELF-DEFENSE OFFICIALS IN JAPAN SUMINORI KoNo,‘*
KOICHI SHINCHI,~ NARIAKIIKEDA,’ FCJMIOYANAI~
and KOJI IMANISHI~ ‘Department of Public Health, National Defense Medical College, Tokorozawa, Saitama 359, Japan and %Af-Defense Forces Fukuoka Hospital, Kasuga-sbi, Fukuoka 816, Japan (Received in revisedform 27 February 1991)
Abstract-Physical activity and dietary habits were compared between 80 men with adenomatous polyps of the sigmoid colon and 1148 men with normal colonoscopy among male retiring self-defense officials. Physical activity as expressed in terms of time spent doing strenuous activities during leisure time was inversely related to the risk of adenomatous polyps. Controlling for rank, smoking, alcohol and body mass index (BMI), odds ratios for the categories of 0, l-59, 60-l 19 and 2 120 minutes per week were 1.0, 0.88, 0.70 and 0.44, respectively (trend p = 0.015). Among a limited range of foods and beverages, the consumption of rice, green tea and instant coffee tended to be associated with a decreased risk of adenomatous polyps. Although the associations observed with dietary habits still need to be substantiated, the findings on physical activity lend further evidence to the hypothesis that physical activity may be protective in the development of colon cancer. Colon polyps
Physical activity
Diet
INTRODUCTION
Colon cancer is one of the most common cancers in western countries, and mortality from this cancer in Japan has rapidly increased over the past decades, following the westernization of this country [I, 21. Diet has been a main focus in epidemiology of colon cancer, and it has been suggested that diets high in animal fat and low in fiber increase the risk of colon cancer although epidemiological evidence is not congruent [3]. Recently, the role of exercise in the etiology of colon cancer has drawn considerable interest. Several epidemiological studies have reported that low physical activity is associated with an increased risk of colon cancer [4-lo], *All correspondence should be addressed to: Suminori Kono, M.D., Department of Public Health, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359, Japan. CE U/II--I
Japanese men
while other studies failed to find such an association [II, 121. Adenomatous polyps are a well-established precursor lesion of adenocarcinoma of the large bowel [13, 141. In epidemiological aspects, the use of this precursor lesion as an end-point preceding the occurrence of colon cancer has methodological virtues due to the reduction in the time period between exposure and outcome. Surprisingly, however, there have been only a few epidemiological studies of colon polyps regarding diet and physical activity. To our knowledge, two case-control studies [15, 161 and one autopsy study [17] have so far directly examined the relation between diet and adenomatous polyps of the large bowel. The latter study was based on prospective data in a cohort of Japanese men in Hawaii [lo], and this study examined the relationship with physical activity but observed no association [17]. In a
1255
KONOet al. SUMINOR~
1256
population of middle-aged Japanese men, we examined the risk of adenomatous polyps of the sigmoid colon in relation to physical activity and dietary habits. MATERIALS
AND MJZTHODS
Subjects were male self-defense officials who received, between October 1986 and December 1988, a retirement health examination at the Self-Defense Forces (SDF) Fukuoka Hospital, which is part of a nationwide program offering free comprehensive medical examinations for those retiring from the SDF. The age at retirement is mostly early 5Os, and the health examination is done within the year before retirement. In October 1986, we included a lifestyle survey in the SDF Fukuoka Hospital program and started systematic collection of individuals’ medical data. The health examination was done during a 5-day admission and included colonoscopy among others. The following information was extracted from the medical records for data processing; height, body weight, systolic and diastolic blood pressures, blood group, serum biochemical data, results of 75 g oral glucose tolerance test, colonoscopy and ultrasonography of the biliary tract, current medication for selected diseases and past medical history. Details on the procedure and results of colonoscopy have been described elsewhere [ 181. In brief, routine colonoscopy was to examine the rectum and sigmoid colon, and more proximal sites were explored if the subjects tolerated physical discomfort. Colonoscopy with intubation of less than 40 cm was regarded as unsatisfactory, and polyps located at 1l-60 cm from the anus were arbitrarily defined as polyps of the sigmoid colon. In the series of 1460 men, 1348 men underwent satisfactory colonoscopy. With the exception of 6 men who had a history of colectomy or polypectomy of the large bowel, 154 men were found to have at least one polyp, and 1188 were free of pathological lesions; 88 men had histologically confirmed adenomatous polyps of the sigmoid colon. The present study excluded those having conditions which may iniIuence physical activity and dietary habits (chronic bowel disease, post-surgery or newly diagnosed cancer, history of apoplexy, history of myocardial infarction, other coronary heart disease on medication and known diabetes mellitus). Two cases of colon polyposis were also excluded, and the study subjects consisted of 80 cases of
adenomatous polyps of the sigmoid colon and 1148 controls with normal colonoscopy. Self-administered questionnaires were distributed on the first day of admission and collected on the second day with a supplementary interview for unaswered questions. The questionnaire queried smoking and drinking habits, physical activity, dietary habits and medical history. Assessment of smoking and drinking habits and their relation to adenomatous polyps have been published previously [18]. Assessment of physical activity Besides recreational activities, questions on physical activity asked about the average amount of time per day spent asleep, different ways of transport (walking, cycling and running), 5 different levels of activity at work (sedentary, standing, walking, light manual work and heavy manual work), housework and stair-climbing. Regarding recreational activities, frequency (closed-ended question) and duration (open-ended question) were queried for 21 listed activities, if any of them had been performed at least once per month throughout the past year. Any unlisted regular recreational activites were also inquired for. Individuals were further asked whether they had currently refrained from physical exercise due to health problems, and, if so, the period of refraining and health problems were specified. In order to choose an appropriate variable of physical activity in examining the relation with the risk of adenomatous polyps, various indices as to energy expenditure and the amount of time spent for selected activities were validated against serum HDL-cholesterol level, because physical activity is well known to increase it [19]. In accordance with the method used in the Five-City Project [20], activities were classified into 4 levels of intensity by referring to MET values (ratio of working metabolic rate/resting metabolic rate) in the published literature [20,21]. Examples of the intensity classification are given in Table 1. Sleep was coded as 1 MET, and the residual hours per day obtained by subtraction (24 hours minus those spent for reported activities) were regarded as being spent for light activities. Energy expenditure (kcal/kg/day) for selected activities was estimated on the basis of 1 MET = 1 k&/kg/day by summing the products of hours spent for each category of intensity and the corresponding MET score (light = 1.5, moderate = 4, hard = 6 and very hard = 10).
Physical Activity, Diet and Colon Polyps
1257
Table 1. Classification of the intensity of physical activities Example of activities METS value
Occupational
Recreational
Light
1.0-2.9
Desk work, janitorial work
Walking for pleasure, bowling, fishing
Moderate
3&5.0
Walking, housework
Cycling, dance, golf, pingpong, tennis (doubles)
Hard
5.1-6.9
Light manual work (carpentry, painting)
Jogging, tennis (singles), karate
Very hard
7.g
Heavy manual work (digging, carrying heavy load)
Running, football, swimming, body-buiklina. iudo
Intensity
Results shown in Table 2 were based on the analysis of 1316 men excluding those having the following conditions: hypertension on medication, known diabetes mellitus, post myocardial infarction, other coronary heart diseases on medication, thyroid disease, nephrosis/nephritis and any diseases under steroid therapy [19]. The amount of time spent for hard and very hard recreational activities was most strongly associated with serum HDL-cholesterol, and this simple index was used as a variable of physical activity in examining the association with adenomatous polyps. After adjustment for smoking, drinking and body mass index (BMI, body wt (kg)/height (m*)), mean concentrations of HDL-cholesterol for the categories of 0, l-59, 60-l 19 and 2 120 minutes per week were 51.5, 53.3, 54.2 and 56.9mg/dl, respectively.
raw vegetables, fruits, raw fish, soy saucecooked fish, broiled fish and meats, as an average over the past year. Preceded answers were used for consumption frequency, and the quantity was answered in terms of a conventional serving unit. The consumption of foods and beverages was categorized into three levels as shown in Table 3. Men drinking black tea were too few to justify the analysis. Reproducibility of dietary assessment was tested on 49 men who received the health examination in January 1989 with an interval of l-2 months, using a modified questionnaire which contained essentially the same dietary questions. Reproducibility as expressed by the intraclass correlation coefficient was generally good except for meat consumption.
Assessment of dietary habits
Logistic regression analysis was used to control for possible confounding effects of rank, smoking and alcohol consumption. Because obesity has been suggested as a potential confounder in the association between physical activity and colon cancer [22], BMI was also considered in the analysis on physical activity.
Dietary questions included frequency of consumption and amount consumed for five nonalcoholic beverages (brewed coffee, instant coffee, black tea, green tea and milk), rice and soy paste soup, and also the frequency of consumption regarding bread for breakfast, pickles,
Table 2. The associations
between serum HDL-cholesterol variables (n = 1316)
Activities taken into account source
Statistical analysis
Intensity
Energy expenditure (kcal/kg/day) Recreational M+H+V H+V Recreational and M+H+V occupational H+V Total? Amount of time spent (&z/week) Recreational M+H+V H+V
and various physical activity
Pearson’s correlation coefficient
Analysis of covariance*
0.118 0.134 0.100 0.076 0.097
15.96(0.0001) 24.27(0.0001) 9.71(0.002) 5.73(0.02) 9.52(0.002)
0.088 0.135
8.19(0.004) 26.OO(O.OOOi)
F-value (p-value)
Intensity: M = moderate, H = hard, V = very hard. *Independent variables were smoking (never, past and current: ~20 or 220 cigarettes/day), alcohol consumption (never, past and current: -z 30, 30-59 or 2 60 ml of alcohol/day), BMI (kg/m*) and a variable for physical activity. tIncluding sleep, all reported activities, and the residual activities obtained by subtraction.
SUM~NORI KONO et
1258
al.
Table 3. Consumption category of foods and beverages, and renroducibihtv of dietarv assessment Consumption category Food or beverage
Low
Intermediate
High
Intraclass correlation coefficient*
Rice Soy paste soup Bread for breakfast Pickles Raw vegetables Fruits Fish, combinedt Meats Brewed coffee Instant coffee Green tea Milk
< 3 bowls/day c 1 bowl/day
