Makoto Futatsuka

Effect of Cigarette Smoking on Prevalence of Summer-type Hypersensitivity Pneumonitis Caused by Trichosporon Cutaneum

We investigated the effect of cigarette smoking on the prevalence of summer-type hypersensitivity pneumonitis (SHP) caused by Trichosporon cutaneum. In the adult family members of SHP patients, we found that 27 of 41 (65.9%) nonsmokers were SHP patients, compared with 3 of 11 (27.3%) smokers (p less than .05). Also, the prevalence of anti-T. cutaneum antibody was significantly lower in the smokers (p less than .05). A questionnaire provided to 209 SHP patients revealed that the smoking rates of male and female SHP patients were significantly lower (p less than .01) than rates in the normal Japanese population. However, no difference was found in serum anti-T. cutaneum antibody activities or the bronchoalveolar lavage lymphocyte phenotypes for smoking and nonsmoking SHP patients. It was concluded that cigarette smoking had a suppressive effect on the outbreak of SHP, but smoking caused no further suppression after the disease was established.

Causes of death in Minamata disease: analysis of death certificates

SummaryThe causes of death in Minamata disease were analyzed and compared with those of control subjects. Of the 1422 Minamata disease patients in the Kumamoto Prefecture, 378 had died by the end of 1980. Of these 378, the first death occurred in 1954 with a peak incidence in 1956 when Minamata disease was officially reported for the first time. The number of deaths increased rapidly after 1972 with a second peak in 1976. The male: female ratio was 1.8: 1 and the mean age-at-death was 67.2 years (SD = ± 18.65). The mean age-at-death was younger in the cases of the initial outbreak than in those recently. There were, on the average, 2.8 causes of death per person. Of these cases, 157 (41.5%) had Minamata disease indicated on the death certificate, though 64 (16.9%) had Minamata disease coded as the underlying cause. Minamata disease and the noninflammatory diseases of the central nervous system (CNS) were the main underlying causes of death between 1954 and 1969, while, in the multiple cause data, pneumonia and non-ischemic heart disease were the most prevalent. Cerebrovascular diseases (18.0%) were the main underlying causes of death followed by malignant neoplasms (14.7%), cardiovascular diseases (14.1%) and Minamata disease (14.1%) in 1970 or later, while cardiovascular diseases (18.6%), Minamata disease (14.5%), cerebrovascular diseases (10.4%) and malignant neoplasms (7.1%) were the major multiple causes of death. As compared with the control, the proportions of deaths due to noninflammatory diseases of CNS and pneumonia were higher in the initial outbreak. Although the difference in the causes of death was less apparent recently, malignant neoplasms and hypertensive diseases tended to be lower. These results suggest that there is a need for a long-term follow-up of Minamata disease patients. The data also show the potential value of multiple causes of death coding in analyses of mortality.

Hand Arm Vibration Syndrome among Quarry Workers in Vietnam

Hand Arm Vibration Syndrome among Quarry Workers in Vietnam: Makoto Futatsuka, et al. Department of Public Health, Graduate School of Medical Sciences, Kumamoto University—Few studies have focused on the health effects of vibrating tools on workers in the tropical area. Work conditions and health effects related to rock drill operation were studied in 102 quarry workers, including 73 rock drill operators in Vietnam. We aimed to clarify (1) risk of vibration exposure, (2) occurrence of vibration‐induced white finger (VWF), and (3) characteristics of handarm vibration syndrome (HAVS). Total weighted r.m.s. acceleration of the Chinese ‐or Russian‐made rock drills, was 45–55 m/s2. According to work observation studies, daily exposure time to vibration was 160–210 min. ISO5349 predicted that this exposure level would be associated with a high risk of HAVS in workers. We found no clear evidence of VWF. There may be several reasons why no worker exhibited VWF: (1) warmer work conditions, (2) younger and less experienced workers, (3) seasonal changes in work operations, and (4) healthy worker effect. On the other hand, 5–10% of rock drill operators might be suffering from moderate HAVS which was sensori‐neural type dominant. There may be some characteristic features of HAVS among quarry workers in the tropical area.

Exploring the influence of depressive symptoms on physical disability: A cohort study of elderly in Beijing, China

Objectives: This study examined the influence of depressive symptoms on the prevalence of physical disability in a cohort study of Beijing elderly (1992–2000) and analyses the role of some confounding variables in this relationship. Methods: A cohort of 1828 elderly aged 55 and older who were initially free of any physical disability was followed up for 8 years. Baseline depression was assessed by the Center for Epidemiological Studies Depression Scale. Disability on activities of daily living (BADL and IADL) was measured in 1994, 1997, and 2000 respectively. Results: The cumulative percentages of persons who developed BADL disability and IADL disability during each follow-up interview was significantly greater among depressed than non-depressed individuals. Compare with the 1525 non-depressed individuals, the 303 depressed individuals had a relative risk (95% confidence interval) of 2.52 (2.02, 4.82) for BADL disability and 4.98 (2.46, 10.09) for IADL disability, respectively. Although adjustment for confounding factors reduced the risk to 2.20 (1.33, 3.62) and 4.29 (2.08, 8.86), the detrimental effect of depression on disability remained significant. The items of IADL which connected physical activity had higher impairment among depressed individuals. Conclusions: Depression in elderly persons may increase the risk for prevalent disability. It is very important for elders to prevent and reduce depression for improving the quality of their life and physical function.

Methylmercury exposure and mortality in southern Japan: a close look at causes of death.

This study examines mortality patterns by cause of death to investigate the effect of exposure to methylmercury in a small area of Minamata City (Kumamoto Prefecture, Japan), which has the highest concentration of patients with Minamata disease. Standardised mortality ratios (SMRs) are computed by cause of death for the study area, using the age specific rates of the entire city as a standard. The SMRs for liver cancer and chronic liver disease in the study area are significantly higher than unity and are consistent with the mortality patterns of registered Minamata disease patients. While an excess mortality is observed for cerebral haemorrhage, mortality from cerebral infarction and other cerebrovascular diseases is considerably lower in the study area. The multiple risk factors of liver related diseases and a possible explanation for the cerebrovascular mortality patterns are discussed to suggest further investigation.

Preliminary evaluation of dose-effect relationships for vibration induced white finger in Japan

SummaryHabitual use of many vibrating tools has been found to be connected with the appearance of various disorders affecting the blood vessels, nerves, bones, joints, muscles or connective tissues of the hand and forearm. The vibration exposures required to cause these diseases are not known exactly, either with respect to vibration intensity and the vibration frequency spectrum, or with respect to daily exposure time and total exposure period. The purpose of this study is to investigate available data on the physical conditions in Japan that have caused vibration induced white finger (VWF) and attempt to establish approximate relationships between vibration conditions and prevalence of VWF. The vibration conditions were evaluated using the method of vibration assessment recommended by the International Standardized Organization, which uses the weighted vibration level of the frequency weighted, dominant, single axis component of vibration directed into the hand. A clear correlation between level, prevalence of VWF and exposure period can be found. The results also suggest the relationship between the weighted levels and latent intervals. These dose-effect relationships enable the prediction of the average latent interval for a population group and the range of progression of the disorders—all from a measurement of the vibration entering the hands. In Japanese cases, 4, 8, and 15% of VWF prevalence correspond with 10, 20, and 40% of VWF prevalence in the Draft International Standard ISO/DIS 5349 (1982) within the weighted vibration level range of 2 to 50m · s¨.

Occupational dermatoses among fibreglass-reinforced plastics factory workers

Fibreglass‐reinforced plastics (FRP) factory workers are at high risk of developing occupational dermatoses because of their exposure to many chemicals used in the manufacture of plastics as well as to glass fibre or dust. Patch tests were carried out on 29 workers involved in FRP manufacturing processes where unsaturated polyester (UP) resin was used, to investigate the causes of their skin problems. Of the 22 workers who reported experiencing skin problems, 16 showed positive results to at least 1 chemical, including 6 cases of multiple sensitivity. 2 showed positive reactions to UP base resin, 6 to cobalt chloride, 5 to benzoyl peroxide (BPO), 4 to methyl ethyl ketone peroxide (MEKPO), 2 to para‐tertiary butyl catechol (PTBC), 1 to styrene and 1 to formaldehyde. After taking into account their exposures and reported causes by questionnaires and their patch test results, 7 cases were diagnosed as allergic contact dermatitis (ACD) due to chemicals, 3 as irritant contact dermatitis (ICD) due to chemicals, and 3 as dermatitis due to mechanical irritation (MI) from glass fibre or dust, as well as 9 as ACD and/or MI. 18 of the total of 29 subjects (62.1%), including 2 workers without a history of skin problems, were sensitized to at least 1 chemical. Cobalt, peroxides, PTBC and UP base resin were the common causes of ACD.

An epidemiological study with risk analysis of liver diseases in the general population living in a methyl mercury polluted area.

STUDY OBJECTIVE--The aim was to determine the actual prevalence of liver disease and to investigate the contribution of various risk factors to liver disease among the population in a methyl mercury polluted area. DESIGN--The study was a population based cross sectional mass screening survey. A case-control study was designed to estimate the role of various risk factors for liver diseases. SETTING--The study was confined to a small rural town 10 km north of Minamata City. SUBJECTS--1406 persons aged 50 to 69 years were examined (78.3% of the total population of this age in the locality). MEASUREMENTS AND MAIN RESULTS--Measurements of liver disease were made on the basis of haematological, physical, and ultrasonographic examinations. Data on liver risk factors were collected by questionnaire, and by measurement of body height, weight (obesity), and hepatitis B surface antigen (HBsAg). The prevalence rate of liver tumour was 0.5% in males, liver cirrhosis was found in 0.5% of males and 0.1% of females, and hepatitis was seen in 5.4% of males and 1.0% of females. Frequency rates of risk factors for liver disease among subjects with obesity were significantly higher in the female patient group, and the frequency rate among subjects with alcoholic drinking habits was significantly higher in the male patient group. The odds ratio of past history of blood transfusion showed the highest value among other related factors (7.73) and the attributable risk for this was very high (87.1%); HBsAg was next in rank (odds ratio 3.04; attributable risk 67.1%). CONCLUSIONS--The prevalence of liver disease in this methyl mercury polluted area was not increased, contrary to what was expected based on the standard mortality ratios. The main risk factors for liver disease in this area appear to be alcoholic drinking habits and a history of blood transfusion.

Cohort study of vibration-induced white finger among Japanese forest workers over 30 years

SummaryA retrospective longitudinal study was undertaken to evaluate the changes in the prevalence of vibration-induced white finger (VWF) during the period from 1955 to 1988 among a population of Japanese state forestry workers. Since the late 1970s, technical improvements in the engine and the introduction of devices to dampen vibration have reduced the acceleration of chain saw handles from 20 ms−2 rms to less than 3 ms−2 rms. During the study period, the peak prevalence rate was 30.9% in 1973 and 17.2% in 1988. The peak prevalence rate was 54.8%, found in the exposure cohort beginning in 1959–1960 and the peak incidence rate was 5.65 per 100 person year in 1965–1966. Beginning with the 1969–1970 exposure cohort, both the prevalence and the incidence rate decreased significantly. During the study period, prevalence rates were approximately 10, 20, 30 and 35% after 4, 6, 10 and 12 years of exposure, respectively. The latent interval for the development of VWF was 6.2 ± 3.9 years on average, and the duration of VWF was 13.1 ± 7.5 years on average through the 1988 observation period. The 1950 cohort group had a long latent interval and a long prevalent period. On the other hand, the late 1960 cohort group had a short latent interval and a short prevalent period. Of 535 study subjects with VWF during the 20 observation years (prevalence rate: 41.0%), the recovery rate was 38.9% on average from the time of cessation of exposure.

Relationship between Questionnaire Survey Results of Vibration Complaints of Wheelchair Users and Vibration Transmissibility of Manual Wheelchair

ObjectiveClarify the relation between the complaints of wheelchair users and the vibration characteristics of the wheelchair, to improve wheelchair comfort and design.MethodsThe question naires were distributed to 33 wheelchair users directly by the experimenter in order to identify the causes of complaints from wheelchair vibrations that they experienced. The vibration transmissibility of wheelchairs of ten subjects was measured to clarify the causes of complaints of wheelchair vibration according to the ISO 10326-1 standard in the laboratory using a broadband random vibration spectrum with a frequency-weighted vibration magnitude of 0.1 ms−2 r.m.s. over the frequency range from 0.2 to 100 Hz. Each vibration exposure lasted 60 seconds.ResultsThe following findings were clear from the questionnaire results; (i) the vibration rom the wheelchair affected psychological comfort; (ii) the effects of different riding surfaces were important engineering issues affecting wheelchair ride comfort; (iii) the wheelchair users felt the vibration during wheelchair usage at locations on the neck, lower back and buttocks; (iv) vertical vibration was the most noticeable vibration from the wheelchair to each participant’s body. The following findings were clear from the results of the transmissibility measurement of the wheelchair; (i) the resonance frequency-ranges of the transmissibility of the wheelchair showed significant differences between the subjects; (ii) intra-subject variability from three repeated transmissibility measurements was small; (iii) the first resonant frequency occurred approximately 5 to 7 Hz and the second resonant frequency occurred at around 8 Hz and the third resonant frequency occurred approximately 13 to 15 Hz; (iv) the magnitude of the peak transmissibility varied from 1.3 to 2.6.ConclusionFrom the comparison of the results of questionnaires and the transmissibility measurement of the wheelchair, the resonance frequency-ranges of the maximum vibration transmissibility of the manual wheelchairs were consistent with the frequency-ranges of the body parts of the causes of the complaints of wheelchair users. In addition, from these experimental results, it was suggested that the main point for improving a wheelchair user’s comfort was to reduce the wheelchair seat vibration transmissibility at around 8 Hz and also to design wheelchair stiffness and damping characteristics to minimize vibration transmission at specific frequencies at body locations that caused the discomfort reported by wheelchair users.