The use of family health services authority registers as a sampling frame in the UK: a review of theory and practice.
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Case-Control Studies↗
Biomedical subjects
L Rushton
Publications and source records attributed to L Rushton.
Use of multiple causes of death in the analysis of occupational cohorts--an example from the oil industry.
OBJECTIVES: To examine the efficacy of routine examination of multiple causes of death occurring on death certificates in cohort studies, with an example from the oil industry. METHODS: The underlying and multiple causes were coded for all notified deaths from a cohort of 35,000 men employed at eight oil refineries in the United Kingdom. Matrices of the frequencies of underlying causes by contributory causes were analysed for the total population and by subgroups defined by refinery, occupation, age, and calendar period of death. RESULTS: Over 75% of the 10,128 certificates had two or more causes but this varied by disease. Many ratios of mentions of total to underlying causes were similar to those of England and Wales. Ratios for cancer of the larynx and pneumonia were lower, indicating possible over-reporting of these diseases as the underlying cause. Investigation of an excess of pneumonia deaths at one refinery indicated possible miscoding of the underlying cause or the wrong position of pneumonia on some certificates, particularly in combination with malignancy and stroke. CONCLUSIONS: Routine analysis of multiple causes of death can provide useful additional information in cohort studies.
Age Factors↗
A 39-year follow-up of the U.K. oil refinery and distribution center studies: results for kidney cancer and leukemia.
This paper presents briefly some of the principal results of a mortality analysis of a cohort of workers employed for at least 1 year between 1950 and 1975 at eight oil refineries and approximately 750 distribution centers in the U.K., together with detailed results for kidney cancer and leukemia. Over 99% of the workers were successfully traced. Their mortality was compared with that of all males in the national population. The mortality from all causes of death is lower than that of the comparison population in both studies, and reduced mortality is also found for many of the major nonmalignant causes of death. In the refinery study, some increased mortality patterns are found for diseases of the arteries, and no healthy worker effect is found in the distribution center study for ischemic heart disease. Mortality from all neoplasms is lower than expected overall in both studies, largely due to a deficit of deaths from malignant neoplasm of the lung. Mortality from malignant neoplasm of the kidney is increased overall in the distribution center study, and in drivers in particular. The mortality from this disease increases with increased time since first exposure. The observed deaths from leukemia are slightly less than expected in the refinery study and slightly more than expected in the distribution center study. One refinery shows increased mortality due to in myeloid leukemia, and mortality is increased among refinery operators. Mortality is also raised in distribution center drivers, particularly for myeloid leukemias, including acute myeloid leukemia.
Cause of Death↗
Oral contraceptive use and breast cancer risk: a meta-analysis of variations with age at diagnosis, parity and total duration of oral contraceptive use.
OBJECTIVE: To review published reports of risk of breast cancer with oral contraceptive use. DESIGN: Meta-analysis of study results, using regression techniques to explore the inter-study heterogeneity. SETTING: Twenty-seven epidemiological studies of breast cancer risk and oral contraceptive use published 1980-1989. MAIN OUTCOME MEASURES: Relative risk of breast cancer with oral contraceptive use; variations by age at diagnosis, parity, and total duration of use, and with study design characteristics. RESULTS: The overall relative risk estimate was 1.16 (95% CI 1.07-1.25) for the less than 45 years group, 1.21 (95% CI 0.99-1.47) for the nulliparous subgroup, and 1.27 (95% CI 1.12-1.44) for durations of use of more than 8 years. Source of subjects, their marital status, the type of study, data collection methods, matching for geographical area, the number of adjustment factors used in the study analysis, the country of study and the calendar period in which the study ended were all important explanatory factors for inter-study variation, but a substantial proportion of inter-study variation remained unexplained. CONCLUSIONS: These meta-analyses suggest that risk of breast cancer may be raised by around 20% in younger, nulliparous and long use duration subgroups of oral contraceptive users. Risk estimates appear to be influenced by several study design factors, which should be considered carefully in designing and reviewing future studies.
Age Factors↗
Epidemiological survey of oil distribution centres in Britain.
A mortality study of workers employed for at least one year between 1 January 1950 and 31 December 1975 at oil distribution centres from three oil companies in Britain has been carried out. Ninety nine per cent of the population were successfully traced to determine their vital status at 31 December 1975. The mortality observed in the study population was compared with that which would be expected from the mortality rates for all the male population of England and Wales. The overall mortality observed was considerably lower than expected on this basis as was the mortality from stroke, hypertensive disease, bronchitis, and pneumonia. The observed number of deaths from all neoplasms was also much less than expected as were the observed deaths from lung cancer. The observed deaths from ischaemic heart disease approximately equalled those expected overall and in each of the companies, however, and there was no evidence of a "healthy worker effect" for this disease group. The ratio of observed over expected deaths from ischaemic heart disease tended to decrease with increasing age at death, and for most of the job groups overall, the observed and expected deaths were about the same. Raised mortality patterns from ischaemic heart disease were found in several subgroups of the population of one company. Mortality from myelofibrosis and diseases of the lymphatic and haematopoietic tissue was slightly raised overall. Only myelofibrosis showed an overall excess but raised mortality was found in subgroups of the population defined by company, job, and length of service in several of the other neoplasms making up this disease group. The numbers of deaths from these causes were all small, making it difficult to exclude chance effects. Further work would be required to ascertain whether these results are due to an occupational factor and if so to identify the physical or chemical nature of the risk.
Accidents, Traffic↗
Epidemiological survey of maintenance workers in London Transport Executive bus garages and Chiswick Works.
A mortality study of maintenance men employed for at least one year between 1 January 1967 and 31 December 1975 at 71 London Transport bus garages and Chiswick Works has been carried out. Over 97% of the population were successfully traced to determine their vital status at 31 December 1975. The mortality observed in the study population was compared with that which would be expected from the mortality rates for the all male population of England and Wales. The mortality of the study population from all causes was much lower than expected on this basis, as was the mortality from cerebrovascular disease, ischaemic heart disease, and bronchitis. Mortality from all neoplasms was slightly less than expected overall and especially in the younger age groups. The observed deaths from cancer of the lung were approximately the same as those expected on the basis of national rates. Nevertheless, a deficit of observed deaths from lung cancer was obtained after adjusting for the higher mortality from this disease in Greater London. Raised mortality was found in subgroups of the population for several malignant disease groups but these were almost all based on small numbers of deaths, making it difficult to exclude chance effects. Both the number of men and deaths in the study were limited and the follow up time was also short. Considerable extension of the study to include more men and increase the follow up time would be required for any definite mortality patterns to emerge.
Bronchitis↗
Length of follow-up in cohort studies.
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Follow-Up Studies↗
Simultaneous inference in epidemiological studies.
Some difficulties encountered in using and interpreting significance tests in both exploratory and hypothesis testing epidemiological studies are discussed. Special consideration is given to the problems of simultaneous statistical inference--how are inferences to be modified when many significance tests are performed on the same set of data? Although some partial solutions are available, greater emphasis on estimation methods and less use of and reliance on significance testing in epidemiological studies is more appropriate.
Epidemiology↗
Mortality patterns in eight U. K. oil refineries.
The patterns of mortality are described for 35,000 male employees, with a minimum of 1 year's continuous service, who worked at 8 refineries in the U. K. in the period 1 January 1950-31 December 1975. The trace rate of those involved was 99.8%. Overall the ratio of observed to expected deaths was 0.84 (O = 4406, E = 5259.9 P less than 0.00001). The numbers of deaths for many of the chronic degenerative diseases were lower than "expected." The number of observed deaths from all cancers were appreciably less than expected (O = 1147, E = 1286.4, O/E = 0.89, P = 0.00006). Lung cancer was particularly reduced (O = 416, E = 532.7, O/E = 0.78, P less than 0.00001); there was no excess of leukemia ( in workers including some exposed to benzene). Other comparable studies have suggested an excess of gastrointestinal cancer. In the present study deaths from esophageal, stomach, intestinal, and rectal cancer were slightly raised for all workers (O = 346, E = 328.6, O/E = 1.05, P less than 0.4); this was particularly true for those joining before 1950 with long service and increased latent interval. There were also excesses based on small numbers of deaths from nasal cancer (O = 7, E = 3.1, O/E = 2.24, P less than 0.05), and melanoma (O = 14, E = 6.5, O/E = 2.16, P less than 0.01). There was no evidence of an excess of brain tumors (O = 36, E =- 44.8, O/E = 0.80, P less than 0.2).
Brain Neoplasms↗
A case-control study to investigate the association between exposure to benzene and deaths from leukaemia in oil refinery workers.
All deaths with a mention of leukaemia on the death certificate, in men employed over a period of 25 years of 8 oil refineries in the U.K. were identified. The potential benzene exposure of these cases was compared with that of two sets of controls selected from the total refinery population. One set of controls was matched for refinery and year of birth, the other set was matched for refinery, year of birth nd length of service. No information was available on measurement of benzene in the work environment but a job history was obtained from refinery personnel records for all cases and controls. This was used to allocate each man to a benzene exposure level of "low", "medium", or "high". There was no overall excess of deaths from leukaemia when compared with the expectation from national rates. There was also no excess of cytological types of leukaemia which have been shown to be particularly associated with benzene exposure. However, the risk for those men with medium or high exposure relative to the risk for those with low benzene exposure approached a significance (P=0.05) when length of service was taken into account. If there were an increased risk of leukaemia due to benzene exposure, it could have only been one that affected a very small proportion of men within the refinery workforce.
Benzene↗
An epidemiological survey of eight oil refineries in Britain.
A mortality study of workers employed for at least one year between 1 January 1950 and 31 December 1975 at eight oil refineries in Britain has been carried out. Over 99% of the population were successfully traced to determine their vital status at 31 December 1975. The mortality observed in the study population was compared with that which would be expected from the mortality rates for the all male population of England and Wales, and Scotland, with adjustment for regional variation in mortality for the English and Welsh refineries. The overall mortality observed was considerably lower than that expected on this basis, as was the mortality from heart disease, stroke, bronchitis, and pneumonia. The observed number of deaths from all neoplasms was also very much less than expected, a result almost entirely due to a large deficit of observed deaths from lung cancer. Raised mortality patterns were found in several refineries for cancers of the oesophagus, stomach, intestines, and rectum, although no location was consistently high for all these causes of death. Different year-of-entry cohorts and job groups were also affected. In general, mortality from these causes increased as length of service and interval from starting work increased. There were also significantly more observed deaths than expected from cancer of the nasal cavities and sinus, and melanoma. Further work is required to ascertain whether these are due to an occupational factor and, if so, to identify the physical or chemical nature of the risk.
Aged↗
Late complications of sterilisation by laparoscopy and tubal ligation. A controlled study.
The frequency of late sequelae in 454 patients sterilised by laparoscopy and diathermy or by abdominal tubal ligation was compared with that in 154 controls whose husbands had had a vasectomy. Results showed an increase in menstrual loss and pain with menstruation in the sterilised groups, especially if this had been done by diathermy and division under laparoscopic control.
Adult↗