Biomedical subjects
Publications and source records attributed to J M Elwood.
A nationwide case-control study of childhood leukaemia in New Zealand included measurements of electric and magnetic fields in children's homes. There was no significant association between leukaemia and the time-weighted average of the 50 Hz magnetic or electric fields in the bedroom and living (or daytime) room combined.
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A nationwide case-control study was conducted in New Zealand, to test hypotheses about the role of infections in the aetiology of childhood leukaemia. Children aged 0-14 years with leukaemia were matched on age and sex to controls selected from birth records. Case ascertainment was virtually complete and 121 (92%) of 131 eligible case families took part. The participation rate among the 303 first-choice eligible controls was 69%. Home interviews and serological tests were conducted. Adjusted relative risks were estimated by logistic regression. There was an increased risk of leukaemia in relation to reported influenza infection of the child during the first year of life (adjusted odds ratio 6.8, 95% confidence interval 1.8-25.7). This could be a chance finding due to multiple comparisons, and it should be tested elsewhere. Some key variables relevant to Greaves' hypothesis were not associated with B-cell precursor acute lymphoblastic leukaemia (numbers of infections and vaccinations, firstborn status, attendance at preschool groups), although a small effect could not be ruled out with a study of this size. Leukaemia risk was higher among children in poorer social circumstances, and this was true for all eligible children as well as for the participants.
OBJECTIVES: To investigate the mortality of workers who had been exposed to asbestos, machining fluids and foundry work in a foundry and heavy engineering plant in the railway rolling stock manufacturing industry in New Zealand. METHODS: Historical cohort study design. RESULTS: For the total workforce of 3522 men employed between 1945 and 1991, follow up was 90% of person-years to 31 December 1991. Significantly increased standardised mortality ratios (SMRs) were found for all causes of death combined (SMR 1.07; 95% confidence interval (95% CI) 1.01 to 1.14), all malignancies (SMR 1.15; 95% CI 1.01 to 1.31), circulatory (SMR 1.16; 95% CI 1.07 to 1.27) and musculoskeletal diseases (SMR 3.06; 95% CI 1.39 to 5.84), all digestive cancers (SMR 1.29; 95% CI 1.04 to 1.59), all respiratory cancers (SMR 1.34; 95% CI 1.08 to 1.65), cancer of the oesophagus (SMR 1.97; 95% CI 1.01 to 3.45), and mesothelioma of the pleura (SMR 6.58; 95% CI 1.24 to 19.49). Three deaths from pleural mesothelioma were recorded, with latency times of 51, 53, and 57 years. There were no dose-response relations between exposure to asbestos, machining fluids or foundry work, or by duration of employment in the plant, and any cause of death. CONCLUSIONS: This study found small increases in risk for several causes of death among foundry and heavy engineering workers; however, these increases were small and the possible effects of smoking and other lifestyle factors could not be excluded. There was evidence of asbestos related disease in those involved in engineering work in the past.
This paper reviews studies that have assessed associations between likely exposure to radiofrequency (RF) transmissions and various types of human cancer. These studies include three cluster investigations and five studies relating to general populations; all of these studies consider place of residence at the time of cancer diagnosis in regard to proximity to radio or television transmitters. There are also five relevant occupational cohort studies and several case-control studies of particular types of cancer. These studies assessed a large number of possible associations. Several positive associations suggesting an increased risk of some types of cancer in those who may have had greater exposure to RF emissions have been reported. However, the results are inconsistent: there is no type of cancer that has been consistently associated with RF exposures. The epidemiologic evidence falls short of the strength and consistency of evidence that is required to come to a reasonable conclusion that RF emissions are a likely cause of one or more types of human cancer. The evidence is weak in regard to its inconsistency, the design of the studies, the lack of detail on actual exposures, and the limitations of the studies in their ability to deal with other likely relevant factors. In some studies there may be biases in the data used
The risks (penetrance) of breast and ovarian cancer in carriers of the BRCA1 or BRCA2 genes are high, but it is likely that estimates based on selected large multicase families are inflated by selection bias. Estimates based on a population survey of Ashkenazi Jews are lower, but other population-based estimates are still not available. The proportion of breast or ovarian cancers related to the genes is similarly lower in population-based samples than in referred selected families, and, even for subjects with cancer onset at young ages or with a family history, it is quite small. Other genes with lower prevalence are also important, and there is evidence of some gene environmental interactions. The management of female BRCA gene carriers includes intensive surveillance, prophylactic surgery and the use of tamoxifen. Apart from screening justified by randomized trials in the general community, such as mammography, recommendations for surveillance and prophylactic surgery are based only on expert opinion, and there has been little consideration of risk-benefit or cost-benefit comparisons. Tamoxifen reduced breast cancer incidence in one trial of high-risk women, but not in two other smaller trials, and the effect on mortality has not been determined. The limitations of genetic testing, and particularly of intervention strategies, deserve close scrutiny.
Criteria set by clinical services for referral for counselling and genetic testing are variable and often arbitrary. Empirical data and computer models are available to estimate the probability of being a mutation carrier, based on family and personal history. Surveys show that high proportions of women at risk of cancer and of women in the general population are interested in being tested, but this may be based on inflated perceptions of personal risk and limitations in understanding of the tests used and their implications. A high proportion of women with a positive family history have a greatly overestimated perception of their own risk, and even expert counselling has little impact on this. This risk perception may produce psychological distress and may reduce participation in screening programs. Counselling, while improving understanding, may also have little impact on prior interest in being tested. Interest in being tested relates to a wish to assess the risk for children, and hazards include potential health insurance discrimination. Testing may result in a reduction of psychological disturbance in those shown to be non-carriers, with little change in those shown to be carriers, but unwillingness to be tested may be related to psychological distress. The impact of publicity concerning genetic testing on perceptions of risk and on psychological disturbance, and the subsequent impact of counselling and intervention, require further assessment.
Centres offering expert counselling and genetic testing are already experiencing high levels of demand, and yet the potential demand is much greater. There have been few attempts to estimate the potential demand created by particular guidelines for referral or testing. A model of need and demand for genetic services is presented, and research questions are identified that should assist in better prediction of future requirements for genetic counselling and testing. The value of integrated routine data on referral criteria, demand and clinical service load is considerable. Attention needs to be paid to referral at primary care and general specialist levels as well as to expert centres.
A study of all newly incident melanoma patients in British Columbia in 1991-1992 was undertaken to test the hypothesis raised by an earlier study, which showed that in younger patients the incidence rate of melanoma per unit area of skin was higher on intermittently exposed skin areas than on continuously exposed areas. Using 1,033 patients and a more detailed body site categorisation than was previously possible, our results confirmed that in both men and women under age 50 the highest melanoma density was on the back. At ages over 50, the greatest density occurred on fully exposed sites, such as the face, though the dorsum of the hand and forearm, likely also to have high exposure, show very low melanoma densities. Differences between males and females correlate well with differences in likely exposure patterns. These results were seen for all invasive cutaneous melanomas combined; the patterns were similar for subtypes and for both invasive and in situ melanoma, with the exception of lentigo maligna melanoma (LMM), which occurs almost exclusively on the face, even at younger ages. Comparison with the earlier study (1976-1979) shows that the age-standardised rates for melanoma excluding LMM have increased by 60%, with the greatest proportional increase being at younger ages; in the recent data, the age-standardised rate for intermittently exposed sites exceeds that for usually exposed sites. Our results confirm that intermittent sun exposure has a greater potential for producing melanoma than continuous exposure at ages below about 50, though at older ages melanoma is more common on body sites with continuous sun exposure.
AIM: To document the clinical outcome of the Otago-Southland Breast Cancer Screening Programme through its first two rounds of screening, from 1991-1996. METHODS: Review and analysis of clinical and pathological records. RESULTS: In the first round of screening, 13,876 women were screened, giving 75% uptake; 12.2% were referred for assessment and 126 cancers detected, 9.1 per thousand women screened. For the 9946 incidence screens in the second round, 3.9% of women screened were referred to assessment and 50 cancers detected, 5.0 per thousand women screened. The uptake and cancer detection rates exceed the targets and exceed other published results; the size distribution of the cancers detected was comparable to the Swedish two-counties study, showing that the results should produce an ultimate mortality reduction. The referral rate to assessment was higher than expected in the first round of screening, but within the targeted range in the second round. The benign to malignant ratio for all biopsies was 1.4:1 for the prevalence screen of the first round and 1.2:1 for the incidence screens in the second round, both exceeding the targets set. CONCLUSIONS: The results show that the uptake and clinical results of the programme exceed expectations and that a large number of small invasive tumours have been successfully detected. These results are comparable to the best of overseas studies, and give confidence that mortality reductions will ultimately occur.
OBJECTIVES: To assess childhood cancer risks for electromagnetic field (EMF) exposures. METHODS: A case-control study was conducted in New Zealand. Cases (aged from zero to 14 years) were ascertained from national databases including the New Zealand Cancer Registry; 303 took part (participation rate, 88 percent). The 303 age- and gender-matched controls were selected randomly from birth records (participation, 69 percent). Mothers were interviewed about appliance exposures (all cases and controls), and 24-hour residential measurements of EMFs were made (leukemia cases and matched controls). RESULTS: For the various appliance exposures, there were some odds ratios (OR) above 1.0 and others below 1.0. For electric blanket use by the child before diagnosis, the adjusted ORs were: leukemia, 2.2 (95 percent confidence interval [CI] = 0.7-6.4); central nervous system cancers, ORs = 1.6 (CI = 0.4-7.1); and other solid cancers, OR = 2.4 (CI = 1.0-6.1). Leukemia risk was increased for the highest category of the mean measured bedroom magnetic field (> or = 0.2microT cf < 0.1 microT), with an adjusted OR of 15.5 (CI = 1.1-224). A gradient in OR with exposure was not shown (middle category: OR 1.4, CI = 0.3-7.6), and there was no association with exposure categorized into thirds based on controls' exposure. The adjusted OR for leukemia in relation to the measured daytime room magnetic field (> or = 0.2 microT cf < 0.1 microT) was 5.2 (CI = 0.9-30.8). CONCLUSIONS: This was a small study and multiple comparisons were made. The positive findings thus should be interpreted cautiously.
To assess the association between the incidence of cutaneous melanoma; intermittent, occupational and total sun exposure; and history of sunburn at different ages, we conducted a systematic review using results of all published case-control studies which have assessed incident melanoma, sun exposure and sunburn. Twenty-nine studies contributed data on sun exposure and 21 on sunburn. Overall, there was a significant positive association (odds ratio [OR] = 1.71) for intermittent exposure, a significantly reduced risk for heavy occupational exposure (OR = 0.86) and a small, marginally significant excess risk for total exposure (OR = 1.18). There was a significantly increased risk with sunburn at all ages or in adult life (OR = 1.91) and similarly elevated relative risks for sunburn in adolescence (OR = 1.73) and in childhood (OR = 1.95). There was significant heterogeneity with all of these estimates except that of all ages or adult sunburn. These results show the specificity of the positive association between melanoma risk and intermittent sun exposure, in contrast to a reduced risk with high levels of occupational exposure. The association with sunburn also is likely to reflect intermittent exposure; the results do not suggest any strong relationship to age at sunburn. These associations are similar to those reported for basal cell skin cancer but different from those reported for squamous cell cancer. The mechanisms by which intermittent exposure increases risk, while other patterns of exposure do not, remain to be elucidated.
A comparison of the site distribution of cutaneous malignant melanoma in New Zealand and Canada was performed. This series deals with 41,331 incident cases registered between 1968 and 1990 and is the largest to date to evaluate the influence of age and gender on the site distribution of melanoma. Site-specific, age-standardized rates per unit surface area and relative tumour density were assessed by gender and country and differences compared with statistical techniques adapted to this context. The age-standardized rates for all sites were higher in New Zealand than in Canada, the ratio being 3.2 for men and 3.8 for women. Occurrence of melanoma was denser for chronically than intermittently exposed sites in both New Zealand and Canada. The highest incidence rate per unit area was for the ears in men which was more than 5 times the rate for the entire body in each country. For each gender, melanomas were relatively commoner on the trunk and the face in Canada, and on the lower limbs in New Zealand. The variations in the site distribution were similar in each country and consistent with the effect of differential patterns of sun exposure between genders. Our results show that the levels of risk of melanoma between phenotypically comparable populations exposed to different amount of UV radiation vary in a site-specific manner, especially for intermittently exposed sites. This suggests that both environmental conditions and lifestyle factors influence the site distribution of melanoma in these two populations.
AIMS: To explore how patients with early breast cancer are managed surgically in New Zealand. METHODS: A questionnaire was mailed to 195 surgeons registered as general surgeons. RESULTS: Replies were received from 112 of the 186 currently working surgeons (60%), of whom 76 indicated that they treated patients with breast disease. Six per cent indicated that they treated > 50 newly diagnosed breast cancer patients in 1994. A minority, 29%, had formal protocols documented for the surgical management of breast cancer patients in their unit. One-third would make the decision about treatment themselves, two-thirds would involve other specialties. Almost all would offer the patient a choice of treatment when this was appropriate. Only 9% would recommend mastectomy for a T1/2NO tumour located in the upper outer breast quadrant. There were no significant differences between surgeons when divided by regional health authority, type of hospital and numbers of patients treated annually. CONCLUSIONS: There appears to be agreement amongst surgeons regarding the preferred form of surgical treatment of patients with stage I or II disease. The results indicate that the surgical treatment of early stage disease is consistent with published guidelines.
Contrasting conclusions on the efficacy of routine breast cancer screening in younger women, under age 50, have been produced by expert and influential groups, particularly in the United States. In an international workshop in 1993, and again at a consensus development conference in 1997, the National Institutes of Health and the National Cancer Institute concluded that evidence for efficacy was uncertain, and routine screening could not be recommended. The 1997 conference concluded that the individual decision had to be made by each woman and her health care provider. In contrast, the American Cancer Society has advocated routine screening, despite accepting that the randomized trial evidence does not clearly support it. The decision of the 1997 NCI consensus conference has been rejected by the director of the NCI, and a similar controversy occurred in 1993. On two occasions, US Senate subcommittees have affirmed support for screening and criticized the conclusions of expert groups. In this paper, the arguments raised in these discussions, and the differing ways in which scientific evidence has been assessed, are discussed.
AIMS: To assess factors influencing attendance or nonattendance at the first round of a population based mammography screening programme, in New Zealand. METHOD: Representative samples of women who responded to an invitation to attend screening, and women who did not respond, were interviewed by telephone, by an interviewer independent of the screening programme. The response rates in those identified were 98% for attenders and 86% for nonattenders, giving final samples of 191 and 174 respectively. However, more nonattenders could not be contacted or had no known phone number. RESULTS: Reasons given for attendance were primarily the need for reassurance, to detect breast cancer early, and the fact that the programme was free, a pilot programme, or recommended by their family doctor. Seventeen percent of attenders had been influenced by positive reports from other women. Of the nonattenders, 7% were ineligible for mammography, 20% did not attend because of practical difficulties and convenience, and 20% expressed concern or fear of the procedure or were influenced by negative reports from other women. Attenders and nonattenders did not differ in regard to age, education, income, socioeconomic status, degree of worry when the invitation was received, or physical distance from their home to the screening centre, although nonattenders estimated the travel would take considerably longer than did attenders. Ninety percent of attenders intend to come to the second round of screening. Forty three percent of nonattenders intend to participate at future rounds of screening, this figure being 80% in those who did not attend because of logistic or convenience reasons, and 27% for those who did not attend because of fear or negative reports. CONCLUSIONS: The main reasons given for nonattendance are approximately equally divided between practical difficulty, and negative attitude towards the process. Most of those who did not attend for reasons of convenience intend to participate at future rounds, so that overall almost half of nonattenders intend to participate at future rounds. Therefore we recommend that invitations for future screening rounds should be sent to women who do not participate in the first round of population based screening.
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Explore the source record for details and available documents.