Janice Hansen

Vitamin A and cancer prevention II: Comparison of the effects of retinol and β-carotene

Former blue asbestos workers known to be at high risk of asbestos‐related diseases, particularly malignant mesothelioma and lung cancer, were enrolled in a chemo‐prevention program using vitamin A. Our aims were to compare rates of disease and death in subjects randomly assigned to β‐carotene or retinol. Subjects were assigned randomly to take 30 mg/day β‐carotene (512 subjects) or 25,000 IU/day retinol (512 subjects) and followed up through death and cancer registries from the start of the study in June 1990 till May 1995. Comparison between groups was by Cox regression in both intention‐to‐treat analyses and efficacy analyses based on treatment actually taken. Median follow‐up time was 232 weeks. Four cases of lung cancer and 3 cases of mesothelioma were observed in subjects randomised to retinol and 6 cases of lung cancer and 12 cases of mesothelioma in subjects randomised to β‐carotene. The relative rate of mesothelioma (the most common single cause of death in our study) for those on retinol compared with those on β‐carotene was 0.24 (95% CI 0.07–0.86). In the retinol group, there was also a significantly lower rate for death from all causes but a higher rate of ischaemic heart disease mortality. Similar results were found with efficacy analyses. Our results confirm other findings of a lack of any benefit from administration of large doses of synthetic β‐carotene. The finding of significantly lower rates of mesothelioma among subjects assigned to retinol requires further investigation. Int. J. Cancer 75:362–367, 1998.

Vitamin A and cancer prevention I: Observations in workers previously exposed to asbestos at Wittenoom, Western Australia

Our aim was to describe a vitamin A‐based cancer prevention program for former asbestos workers and to check for possible harmful effects by comparing rates of disease and death in study subjects with subjects who chose not to join. All subjects had been occupationally exposed to crocidolite at Wittenoom Gorge between 1943 and 1966; 1,677 subjects indicated interest in the program and 1,203 joined between June 1990 and May 1995. Comparison subjects consisted of 996 former workers known to be alive in Western Australia in 1990 who did not join the program. Program subjects were provided with annual supplies of vitamin A (either synthetic β‐carotene or retinol), help in quitting smoking and dietary advice. The comparison group received only mail contact. Both groups were followed up to December 1994 for vital status and cancer information, and rates of cancer and death from various causes were compared. Mortality in both groups was higher than expected (standardised mortality ratio 1.23 in program subjects and 1.67 in comparison subjects). After adjustment for age, smoking and asbestos exposure, the relative rates in participants compared with non‐participants was below 1 for all examined cancers and causes of death. For mesothelioma and lung cancer, group differences increased with time from entry, whereas other differences dissipated with time. No significant side effects were reported. In conclusion, program participants had significantly lower mortality than non‐participants, but the rates of the 2 groups converged with time. Int. J. Cancer 75:355–361, 1998.

Individual exposure levels in people environmentally exposed to crocidolite

Abstract The objective of this article is to assign individual airborne crocidolite exposure levels to former residents of the town of Wittenoom, Western Australia. All environmental monitoring programs carried out in the town since 1966 were reviewed and assessed for their suitability for use in estimating individual exposure to crocidolite. These programs measured respirable fibers greater than 5 μm in length. Duration of residence was determined from questionnaires, work history sheets of the Australian Blue Asbestos Company, and the various sources used to assemble a cohort of previous residents. All exposure measurements were calculated assuming continuous exposure over 24 hours per day, 7 days per week. Intensity of exposure and cumulative exposure were estimated for each person in the cohort. All environmental monitoring surveys carried out at Wittenoom have detected some crocidolite fibers. The levels of fibers have shown a continuing decrease since the mining operations ceased in 1966. Most of th...

The Western Australian register of childhood multiples: Effects of questionnaire design and follow-up protocol on response rates and representativeness

Twin registers have been established worldwide to study the roles of genes and the environment in health and behaviour. While questionnaire surveys are thought to be the most cost-effective way of collecting large amounts of data, low response rates can result in response bias. Many different strategies have been proposed to maximise response rates. A register of all multiple births occurring in Western Australia (WA) from 1980 onwards has been established using probabilistic record linkage techniques. Families who had not experienced the death of one or more of their multiples were invited to participate in the Western Australian Twin Child Health (WATCH) study, which studied the genetic and environmental determinants of childhood asthma and atopy. Several questionnaire designs and follow-up methods were assessed. We have shown that it was feasible to use a population-based register of multiple births to contact families for a questionnaire study. Questionnaire length, mode of follow-up, the number of responses required and the of participants all seemed to affect response.

Functional haplotypes in the PTGDR gene fail to associate with asthma in two Australian populations

Background and objective:  Haplotypes in the promoter region of the prostanoid DP receptor (PTGDR) gene have been shown to functionally influence gene transcription and to be associated with asthma in two previous case–control studies in Caucasians. This study tested the association of PTGDR haplotypes with asthma phenotypes in two large Caucasian‐Australian populations. These results were incorporated in a meta‐analysis with previously published data to determine the overall role for these haplotypes in the risk of asthma.

The Western Australian Register of Childhood Multiples

Twin registers have been established worldwide to study the roles of genes and the environment in health and behaviour. While questionnaire surveys are thought to be the most cost-effective way of collecting large amounts of data, low response rates can result in response bias. Many different strategies have been proposed to maximise response rates. A register of all multiple births occurring in Western Australia (WA) from 1980 onwards has been established using probabilistic record linkage techniques. Families who had not experienced the death of one or more of their multiples were invited to participate in the Western Australian Twin Child Health (WATCH) study, which studied the genetic and environmental determinants of childhood asthma and atopy. Several questionnaire designs and follow-up methods were assessed. We have shown that it was feasible to use a population-based register of multiple births to contact families for a questionnaire study. Questionnaire length, mode of follow-up, the number of responses required and the of participants all seemed to affect response.

The Western Australian Register of Childhood Multiples: Effects of Questionnaire Design and Follow-up Protocol on Response Rates and Representativeness

Twin registers have been established worldwide to study the roles of genes and the environment in health and behaviour. While questionnaire surveys are thought to be the most cost-effective way of collecting large amounts of data, low response rates can result in response bias. Many different strategies have been proposed to maximise response rates. A register of all multiple births occurring in Western Australia (WA) from 1980 onwards has been established using probabilistic record linkage techniques. Families who had not experienced the death of one or more of their multiples were invited to participate in the Western Australian Twin Child Health (WATCH) study, which studied the genetic and environmental determinants of childhood asthma and atopy. Several questionnaire designs and follow-up methods were assessed. We have shown that it was feasible to use a population-based register of multiple births to contact families for a questionnaire study. Questionnaire length, mode of follow-up, the number of responses required and the of participants all seemed to affect response.