Epidemiology and Biostatistics Division

18. Epidemiology and Biostatistics Division

　The Epidemiology and Biostatistics Division has planned and conducted independent and collaborative studies on cancer etiology and prevention, with a special focus on dietary factors. Several epidemiological projects are currently in progress, including cross-sectional, case-control, cohort and intervention studies. In addition, collaborative studies in the fields of clinical and basic sciences are being supported by providing statistical design, analysis and data processing support.
Etiological Roles of Foods and Nutrients in Cancer

　Foods and nutrients have been implicated as etiological factors in cancer occurrence and as contributing to the unique patterns of cancer incidence in Japan. However, epidemiological evidence regarding this issue remains limited. The division has therefore initiated a population-based prospective study on diet and cancer (JPHC Study), in collaboration with the Cancer Information and Epidemiology Division and the National Cardiovascular Center, in which approximately 140,000 individuals will be followed-up for 10 years or more. Among 55,000 population cohort members from 4 areas with an 8-year follow-up, 1,808 deaths and 1,821 incident cancers including 422 (23%) stomach and 377 (21%) colorectal cancers had been documented as of December 31, 1997. The validity of semi quantitative food frequency questionnaire and self-reported diseases such as cancer, cardiovascular diseases, diabetes and cataract have been examined.
　Several analyses were conducted in a cross-sectional study of randomly selected men and their wives in five JPHC study areas. Four food frequency categories of fruit intake accounted for 19% of the variation in plasma ascorbic acid after adjustment for study area and alcohol. This predictability was superior to calculated vitamin C or fruit intake by a detailed 3-day dietary record.⁽²²⁹⁾ The interpopulation and intrapopulation variability of intake of 17 nutrients were analyzed using a 3-day dietary record. The percentage contribution of interpopulation to total variance was notable (8-17%) for total energy, carbohydrates, phosphorus and sodium, but was negligible (<4%) for micronutrients.⁽²³⁰⁾ The factors associated with blood pressure were examined in relation to dietary pattern ⁽²³¹⁾ and occupation.⁽²³²⁾
　The serum lipid concentrations in Japanese children were reviewed and discussed in relation to recent dietary changes.⁽²³³⁾ Dietary and occupational risk factors were investigated for cervical⁽²³⁴⁾ and lung ⁽²³⁵⁾ cancer using a case-control design.
Environmental and Genetic Interaction in the Etiology of Human Cancer

　The ethnic differences in cancer occurrence suggest an interaction between environmental and genetic factors. The division has been conducting several epidemiological studies in Brazil, a multi-ethnic nation with 1.2 million people of Japanese ancestry, and reported some evidence of environmental and genetic interaction in lung carcinogenesis. The Ile/Val (Exon 7) polymorphism of cytochrome P450IA1 was further investigated in Japanese (Okinawa, Iwate and Tokyo), Chinese and an Australian Caucasian group. In a case-control study in Okinawa, the genotype encoding Val/Val was associated with a significantly higher risk of lung cancer. The Val-encoding allele was less frequent in the Chinese and rare in Caucasians.⁽²³⁶⁾
An Epidemiological Evaluation of Cancer Prevention Methods

　Practical prevention strategies are generally based on total evidence obtained from observational epidemiological studies, experimental animal studies and mechanistic interpretation. An evaluation based on intervention studies is, however, essential before recommending a strategy to the general public. The available evidence suggests that the risk of stomach cancer is increased in individuals with chronic atrophic gastritis and is decreased in those with a high consumption of fruit and vegetables (probably vitamin C and/or carotene) and a low consumption of salted foods. A randomized controlled trial to assess the effectiveness of vitamin C supplementation on stomach carcinogenesis has progressed to the fourth year for individuals with chronic atrophic gastritis. Another randomized controlled trial to assess the effectiveness of dietary modification (less salt and more vitamin C and carotene) has been launched after a small pilot study with reasonable results.
　The validity of a self-administered diet history questionnaire used in this trial was assessed by a 3-day dietary record⁽²³⁷⁾ and by 24-hour urinary excretion.⁽²³⁸⁾
Epidemiological and Biostastical Support for Basic and Clinical Research

　Epidemiological and biostastical support have been provided for the prognostic analysis of cancer of breast ^(18,20,204) and tongue.⁽²⁰⁸⁾




	18. Epidemiology and Biostatistics Division



		The Epidemiology and Biostatistics Division has planned and conducted independent and collaborative studies on cancer etiology and prevention, with a special focus on dietary factors. Several epidemiological projects are currently in progress, including cross-sectional, case-control, cohort and intervention studies. In addition, collaborative studies in the fields of clinical and basic sciences are being supported by providing statistical design, analysis and data processing support. Etiological Roles of Foods and Nutrients in Cancer 　Foods and nutrients have been implicated as etiological factors in cancer occurrence and as contributing to the unique patterns of cancer incidence in Japan. However, epidemiological evidence regarding this issue remains limited. The division has therefore initiated a population-based prospective study on diet and cancer (JPHC Study), in collaboration with the Cancer Information and Epidemiology Division and the National Cardiovascular Center, in which approximately 140,000 individuals will be followed-up for 10 years or more. Among 55,000 population cohort members from 4 areas with an 8-year follow-up, 1,808 deaths and 1,821 incident cancers including 422 (23%) stomach and 377 (21%) colorectal cancers had been documented as of December 31, 1997. The validity of semi quantitative food frequency questionnaire and self-reported diseases such as cancer, cardiovascular diseases, diabetes and cataract have been examined. 　Several analyses were conducted in a cross-sectional study of randomly selected men and their wives in five JPHC study areas. Four food frequency categories of fruit intake accounted for 19% of the variation in plasma ascorbic acid after adjustment for study area and alcohol. This predictability was superior to calculated vitamin C or fruit intake by a detailed 3-day dietary record.⁽²²⁹⁾ The interpopulation and intrapopulation variability of intake of 17 nutrients were analyzed using a 3-day dietary record. The percentage contribution of interpopulation to total variance was notable (8-17%) for total energy, carbohydrates, phosphorus and sodium, but was negligible (<4%) for micronutrients.⁽²³⁰⁾ The factors associated with blood pressure were examined in relation to dietary pattern ⁽²³¹⁾ and occupation.⁽²³²⁾ 　The serum lipid concentrations in Japanese children were reviewed and discussed in relation to recent dietary changes.⁽²³³⁾ Dietary and occupational risk factors were investigated for cervical⁽²³⁴⁾ and lung ⁽²³⁵⁾ cancer using a case-control design. Environmental and Genetic Interaction in the Etiology of Human Cancer 　The ethnic differences in cancer occurrence suggest an interaction between environmental and genetic factors. The division has been conducting several epidemiological studies in Brazil, a multi-ethnic nation with 1.2 million people of Japanese ancestry, and reported some evidence of environmental and genetic interaction in lung carcinogenesis. The Ile/Val (Exon 7) polymorphism of cytochrome P450IA1 was further investigated in Japanese (Okinawa, Iwate and Tokyo), Chinese and an Australian Caucasian group. In a case-control study in Okinawa, the genotype encoding Val/Val was associated with a significantly higher risk of lung cancer. The Val-encoding allele was less frequent in the Chinese and rare in Caucasians.⁽²³⁶⁾ An Epidemiological Evaluation of Cancer Prevention Methods 　Practical prevention strategies are generally based on total evidence obtained from observational epidemiological studies, experimental animal studies and mechanistic interpretation. An evaluation based on intervention studies is, however, essential before recommending a strategy to the general public. The available evidence suggests that the risk of stomach cancer is increased in individuals with chronic atrophic gastritis and is decreased in those with a high consumption of fruit and vegetables (probably vitamin C and/or carotene) and a low consumption of salted foods. A randomized controlled trial to assess the effectiveness of vitamin C supplementation on stomach carcinogenesis has progressed to the fourth year for individuals with chronic atrophic gastritis. Another randomized controlled trial to assess the effectiveness of dietary modification (less salt and more vitamin C and carotene) has been launched after a small pilot study with reasonable results. 　The validity of a self-administered diet history questionnaire used in this trial was assessed by a 3-day dietary record⁽²³⁷⁾ and by 24-hour urinary excretion.⁽²³⁸⁾ Epidemiological and Biostastical Support for Basic and Clinical Research 　Epidemiological and biostastical support have been provided for the prognostic analysis of cancer of breast ^(18,20,204) and tongue.⁽²⁰⁸⁾