The purpose of this study is to establish the normal physiological values of glycosylated hemoglobin (HbA₁ and HbA_1C) among Japanese rural inhabitants and to evaluate its potential as a screening tool for diabetes mellitus. Six hundred and seventy-five people aged 35-64 years (210 males and 465 females) were examined. Oral glucose tolerance tests were perfomed on 135 inhabitants of them by giving a 50-gm.
Frequency distributions of HbA₁ and HbA_1C fitted approximately to the log-normal distribution.
Geometric means and standard deviations in bracket were 7.95 (1.11)% for HbA₁ in men, 8.13 (1.12)% for HbA₁ in women, 5.17 (1.10)% for HbA_1C in men and 5.16 (1.11)% for HbA_1C in women
Group average values of HbA₁ and HbA_1C tended to increase with age in both men and women except a male group aged 60 years and over. There were no significant differences between mean values of glycosylated hemoglobin in men and those in women. HbA₁ was positively correlated with age in women and negatively correlated with hemoglobin in both men and women. HbA_1C was positively correlated with age in men and women, body mass index, systolic blood pressure and serum cholesterol in women, and negatively correlated with hemoglobin in men.
In order to evaluate glycosylated hemoglobin as a screening tool for the identification of unknown persons with diabetes, we calculated the sensitivity (the extents to which the participants who were found to have a diabetic OGTT also had an abnormal glycosylated hemoglobin) and specificity (the extents to which the participants who were not diabetic had normal glycosylated hemoglobin). The sensitivities for the person aged 59 years or under using HbA₁ were 72.7-100% and the specificities 67.3-75.0 percent. Futhermore the sensitivities for the same aged person using HbA_1C were 81.8-100% and the specificities 78.8-81.3 percent. The validities for both HbA₁ and HbA_1C were higher than those for glucosuria or blood glucose. But glycosylated hemoglobin was not useful as a screening tool for the person aged 60 years and over because of the low specificity.

The purpose of this study is to investigate the prevalence of and to classify the types of silicosis patients who were working at that time as migrant workers in the eastern part of Toyama Prefecture. Migrant workers are known in Japanese as “dekasegi” This term refers to workers who migrate seasonally from their home towns to areas where work is more available.
Questionnaires were sent to all male inhabitants aged 30 or over in the selected five areas. Eighty-seven percent of the questionnaires were answered and returned. Based on the results, 482 inhabitants were selected as migrant workers with experience in jobs where they were exposed to large amount of dust. Chest roentgenography and subjective symptoms were examined in these subjects.
The results obtained were follows;
(1) Eight hundred and eighty-five of the respondents (41%) had worked as migrant workers.Of these, 580 men (66%) had worked in jobs with exposure to dust.
(2) Of the 482 migrant workers whose jobs exposed them to dust, 424 silicosis cases (88%) were found by chest roentgenographic examination. Silicosis is classified into four types according to the national Pneumoconiosis Law on the basis of chest roentgenographic findings. These patients included 195 cases of type 1, 123 cases of type 2, 59 cases of type 3 and 47 cases of type 4 silicosis.
(3) The prevalence of disease symptoms in the silicosis patients included ; cough 39%, phlegm 40%, shortness of breath 41%, palpitations 17% and wheezing in 20% of the cases. The silicosis patients showed a higher frequency of respiratory disease symptoms than those dust-exposed workers who did not evidence signs of silicosis.
(4) The silicosis patients were found in 98% of the migrant workers whose exposure to dust lasted a period of more than 20 years, 89% in men whose work was between 10 and 19 years and 76 % in men who had worked less than 10 years.
(5) The silicosis in 297 cases (70% of the total number of disease patients) was first detected during the examinations in the course of this research.