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Biomedical subjects

N Pearce

Publications and source records attributed to N Pearce.

At least 199 records · Page 11Linked to original sources
PubMed1988

Increased risks of soft tissue sarcoma, malignant lymphoma, and acute myeloid leukemia in abattoir workers.

This paper presents a review and further analysis of a series of New Zealand case-control studies which have found elevated risks for soft tissue sarcoma (STS), non-Hodgkin's lymphoma (NHL), and acute myeloid leukemia (AML) in abattoir workers. The first published study involved 82 cases of STS (ICD 171) and found a relative risk of 2.8 (90% confidence interval 1.3-6.3). Interviews with an additional 51 cases reported here revealed a relative risk of 1.6 (90% confidence interval 0.9-3.0). Two further studies involved interviews with 100 cases of the category of NHL involving lymphosarcoma and reticulosarcoma (ICD 200) and 83 cases of other NHL (ICD 202). Relative risk estimates were 1.8 (90% confidence interval 1.1-2.9) and 1.7 (90% confidence interval 1.0-2.8), respectively. A study of 150 cases of AML (ICD 205.0) found a relative risk of 2.5 for abattoir workers (90% confidence interval 1.3-4.7). Finally, a United States cohort study found a standardized mortality ratio of 2.4 (90% confidence interval 0.8-5.4) for Hodgkin's disease (ICD 201) and 2.2 (90% confidence interval 0.8-4.5) for cancer of other lymphatic tissue (ICD 202, 203, 208) among abattoir workers. Abattoir workers are potentially exposed to oncogenic viruses, including bovine leukemia virus. Some workers may also be exposed to the animal carcinogen 2,4,6-trichlorophenol when treating pelts.

Abattoirs↗
PubMed1988

Multistage modelling of lung cancer mortality in asbestos textile workers.

The Armitage-Doll multistage model of cancer is applied to data from a cohort study of lung cancer in 1261 white male workers from one asbestos textile manufacturing plant. Three approaches are used: induction time analysis; analysis of the relationship of the excess incidence rate to age at first exposure and time since first exposure; and direct fitting of the Armitage-Doll model. Poisson regression was used for all analyses. The induction time analysis was conducted using Rothman's 'window of exposure' method. This suggested that the increase in rate ratio was primarily due to exposures occurring 15-24 years previously, whereas there was little effect from exposures occurring 0-14 or 25+ years previously. The excess incidence rate increased both with age at first exposure and time since first exposure, suggesting that asbestos acted at a stage intermediate between the first and penultimate stages. Direct fitting of the Armitage-Doll model suggested that the best fit was obtained by assuming that asbestos acts at stage 3, 4 or 5 of a six-stage process. Most analyses of the type presented here are unable to determine at which stage a carcinogen acts, due to the small numbers of cancer deaths occurring in typical occupational cohorts. Furthermore, there is reason to doubt the validity of the Armitage-Doll model. However, such analyses can at least suggest whether a carcinogen appears to act at an early, intermediate or late stage, and the general statistical methods applied here will retain their usefulness as further models are developed and larger data sets become available.

Adult↗
PubMed1988

Radiation doses and cause-specific mortality among workers at a nuclear materials fabrication plant.

A historical cohort mortality study was conducted among 6,781 white male employees from a nuclear weapons materials fabrication plant for the years 1947-1979. Exposures of greatest concern are alpha and gamma radiation emanating primarily from insoluble uranium compounds. Among monitored workers, the mean cumulative alpha radiation dose to the lung was 8.21 rem, and the mean cumulative external whole body penetrating dose from gamma radiation was 0.96 rem. Relative to US white males, the cohort experienced mortality deficits from all causes combined, cardiovascular diseases, and from most site-specific cancers. Mortality excesses of lung and brain and central nervous system cancers were seen from comparisons with national and state rates. Dose-response trends were detected for lung cancer mortality with respect to cumulative alpha and gamma radiation, with the most pronounced trend occurring for gamma radiation among workers who received greater than or equal to 5 rem of alpha radiation. These trends diminished in magnitude when a 10-year latency assumption was applied. Under a zero-year latency assumption, the rate ratio for lung cancer mortality associated with joint exposure of greater than or equal to 5 versus less than 1 rem of both types of radiation is 4.60 (95% confidence limits (CL) 0.91, 23.35), while the corresponding result, assuming a 10-year latency, is 3.05 (95% CL 0.37, 24.83). While these rate ratios, which are based on three and one death, respectively, lack statistical precision, the observed dose-response trends indicate potential carcinogenic effects to the lung of relatively low-dose radiation. There are no dose-response trends for mortality from brain and central nervous system cancers.

Adolescent↗
PubMed1988

Case-control studies using other diseases as controls: problems of excluding exposure-related diseases.

Exclusion criteria are examined in case-control studies which include persons with other diseases in the control group. Theoretically, a sample of the study base should not exclude persons who develop exposure-related diseases before, during, or after the time period in which the case occurred. This principle also generally applies when controls are sampled from the subset of persons with other diseases generated by the same study base. In particular, if the incidence rates (assuming completeness of ascertainment) for all other disease combined are similar in the exposed and nonexposed populations, then controls should be sampled from all other diseases, regardless of their relation to exposure. On the other hand, if the composite incidence rate for other diseases is greater (or less) in the exposed population, then it may be necessary to exclude controls with diseases positively (or negatively) associated with exposure. Additionally, considerable care should be taken when sampling controls from persons with specific diseases which are apparently "unrelated" to exposure because confounding may be introduced by exposure-related determinants of the control disease(s). To remove such confounding, it is necessary to control for risk factors for both the study disease and the control disease(s).

Environmental Exposure↗
PubMed1988

Exponential models for analyses of time-related factors, illustrated with asbestos textile worker mortality data.

In any study based on an occupational cohort, it is important to consider the variation in risk factors over time. Cumulative exposure is the most important time-related factor for exposure-response analyses, whereas other time-related factors such as age at risk, year at risk, and length of follow-up may be confounders and effect modifiers. This paper examines the family of exponential models which can be used for time-related analyses of studies based on an occupational cohort. Analyses using Poisson regression, the proportional hazards model, and the logistic model are presented, and their interrelationships explored. These models are illustrated with data from a cohort study of lung cancer mortality among asbestos textile plant workers. All three approaches yielded similar effect estimates. In particular, Poisson regression and the proportional hazards model yielded very similar findings, but Poisson regression has some conceptual and computational advantages.

Adult↗
PubMed1987

Time trends and occupational differences in cancer of the testis in New Zealand.

The findings are reported from a New Zealand Cancer Registry-based case-control study involving 427 male patients with testicular cancer registered during the period 1979-1983 and aged 20 years or more at time of registration. Controls were also males chosen from the Cancer Registry with two controls per case, matched on age and year of registration. It was found that, as in other countries, persons in the upper social class groupings were at increased risk of testicular cancer. Persons in professional occupations were also at increased risk, but the odds ratio of 1.09 was much smaller than found in other studies. The previously reported excess risks for farmers, food and beverage workers, forestry workers, and pulp and paper workers were not supported by the New Zealand data. On the other hand, the previously reported excess risk for sales and service workers including members of the armed forces was supported, to some extent, by the New Zealand data with odds ratios of 1.38 (95% confidence limits 0.98-1.93) and 2.15 (95% confidence limits 0.80-5.79), respectively. Other groups with elevated risk include: physicians (odds ratio = 6.50, 95% confidence limits 1.29-32.6); production supervisors (odds ratio = 2.85,95% confidence limits 1.00-8.13); and motor vehicle mechanics (odds ratio = 2.02, 95% confidence limits 0.93-4.42). However, the New Zealand data generally does not suggest that occupational factors (or lifestyle factors associated with occupation) are of major direct importance in the etiology of testicular cancer. The incidence of testicular cancer has a bimodal age distribution in New Zealand and has risen markedly during the period 1948-1979. The New Zealand data differed from patterns observed in other countries in that the relative increase was approximately uniform across age groups rather than being stronger in the younger age groups.

Age Factors↗
PubMed1987

Very-low-dose hepatitis B vaccine in newborn infants: an economic option for control in endemic areas.

Three 1 microgram or 2 micrograms doses of Merck, Sharp and Dohme plasma vaccine were given to 119 infants of mothers negative for antibody to hepatitis B surface antigen (anti-HBs). Anti-HBs antibodies developed in 25/29 (86%) infants given 1 microgram and in 86/90 (96%) given 2 micrograms doses. Levels of anti-HBs achieved by three 2 micrograms doses were similar to those that have been reported for conventional 10 micrograms doses. Similar levels were recorded from infants of anti-HBs-positive mothers, which suggests that maternal antibody does not interfere with the infant's immune response to low doses of vaccine. Three 2 micrograms doses of vaccine in infancy produce satisfactory immunogenicity and make possible economic control of hepatitis B in endemic areas.

Carrier State↗
PubMed1987

Low-dose vaccination against hepatitis B in children: one-year follow-up.

Six hundred forty-three children, negative for markers of hepatitis B virus (HBV) infections, were given three X 2-micrograms doses of Merck, Sharp and Dohme (MSD) plasma derived hepatitis B vaccine (H-B-Vax) at monthly intervals. Twelve months after the first dose of vaccine, antibody to hepatitis B surface antigen (anti-HBs) was detected in 89% of children by radioimmunoassay (RIA) and in 83% by enzyme immunoassay (EIA). Seroconversion rates and anti-HBs titres were significantly greater in 1-4-year-olds than in older children (p less than 0.01). Eighteen children with no anti-HBs or other markers of HBV at this time were given 10 micrograms of vaccine and tested one month later. Seventeen developed anti-HBs, 12 at levels consistent with an anamnestic response. Forty-nine HBV-marker-negative children seroconverted for antibody to hepatitis B core antigen (anti-HBc) in the 8-month period before or the 12-month period following vaccination. Forty-six of these children were positive for anti-HBs, and one has been confirmed as a chronic carrier of hepatitis B surface antigen (HBsAg). Three cases of clinical hepatitis B in children have been seen in the community since the vaccination programme began. Two of these were amongst the estimated 5% of children who were not vaccinated. The third was in a vaccinee and occurred 4 1/2 months after the last dose of vaccine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Immunogenicity of low doses of hepatitis B vaccine in children: a study in 650 New Zealand children.

Six hundred and fifty New Zealand children from 2-12 years of age were vaccinated three times with 2 mcg intramuscular (IM) doses of Merck Sharp and Dohme plasma-derived hepatitis B vaccine (H-B-Vax), at 0, 1, and 6 months, and tested 2-3 months later for antibody to hepatitis B surface antigen (anti-HBs) by radioimmunoassay (RIA). Overall, 96.5% of the children seroconverted for anti-HBs by RIA, having levels greater than 2.1 RIA S/N units, with 91.2% having values greater than 10 S/N units. Anti-HBs levels were also determined by enzyme immunoassay (EIA), by which method a significantly better response was demonstrated in 2-4-year-olds than in older children. This study demonstrated that a satisfactory anti-HBs response was obtained using one-fifth of the recommended doses of hepatitis B vaccine.

Child↗
PubMed1987

A simple computer program for generating person-time data in cohort studies involving time-related factors.

The use of grouped data methods, such as standardized rate ratios and Poisson regression, for the analysis of cohort studies has a number of attractive features. This approach, however, has not been widely used in the past because of the difficulty of generating person-time data required for the computation of rates, particularly when stratification on time-related factors is involved. This paper presents a simple Statistical Analysis System (SAS) program for the generation of such data in a form that can be read directly by GLIM and used in a Poisson regression analysis. In addition to its simplicity, the program has the advantage of considerable flexibility and involves no restrictions on the number of time-related factors or the number of levels of each factor. Furthermore, it can be modified easily for multiple disease outcomes and for analyses of the latency period, or empirical induction time.

Humans↗
PubMed1987

Is social class standardisation appropriate in occupational studies?

Social class standardisation has been proposed as a method for separating the effects of occupation and "social" or "lifestyle" factors in epidemiological studies, by comparing workers in a particular occupation with other workers in the same social class. The validity of this method rests upon two assumptions: (1) that social factors have the same effect in all occupational groups in the same social class, and (2) that other workers in the same social class as the workers being studied are free of occupational risk factors for the disease of interest. These assumptions will not always be satisfied. In particular, the effect of occupation will be underestimated when the comparison group also has job-related exposures which cause the disease under study. Thus, although adjustment for social class may minimise bias due to social factors, it may introduce bias due to unmeasured occupational factors. This difficulty may be magnified when occupational category is used as the measure of social class. Because of this potential bias, adjustment for social class should be done only after careful consideration of the exposures and disease involved and should be based on an appropriate definition of social class. Both crude and standardised results should be presented when such adjustments are made.

Data Collection↗
PubMed1986

Time-related factors as potential confounders and effect modifiers in studies based on an occupational cohort.

Time-related factors which are potential confounders and effect modifiers in studies based on an occupational cohort are reviewed. The most frequently considered ones include age at first exposure, duration of exposure, interval from exposure to disease recognition, and age at risk. These factors are related to the "healthy worker effect," which appears to be more pronounced among workers with the longest durations of employment and older ages, at date of hire, but weaker with longer length of follow-up and older age at risk. Hence, use of an internal comparison group may not eliminate bias since confounding will occur if the exposed and unexposed groups differ in their distributions across these factors. It is also shown, using the multistage model of carcinogenesis, that these factors may be important effect modifiers. Fortunately, generally straightforward methods of control exist both for stratified analyses and for the commonly used mathematical modeling approaches. Although no firm recommendations can be made, it would appear to be important to control for length of follow-up in the design or analysis of most studies based on an occupational cohort, and controlling for age at first exposure may also be desirable under many circumstances.

Adult↗
PubMed1985

Incidence of hepatocellular carcinoma in New Zealand, 1974-78: ethnic, sex and geographical differences.

The incidence of hepatocellular carcinoma in New Zealand is examined for the period 1974-78. There was a significant north-south gradient for both Maori and non-Maori incidence rates, with the rates in the northern half of the North Island being approximately double those in the South Island. Within each region, Maori rates were approximately three times those of non-Maoris and incidence rates of males were approximately three times those of females. Incidence was particularly high in the Bay of Plenty, Waiapu and Otago hospital board districts. These patterns are generally consistent with available information concerning the distribution of hepatitis B surface antigen (HBsAg) carriage in New Zealand and suggest that HBsAg carriage is likely to be a major risk factor for hepatocellular carcinoma in New Zealand, as it is in other countries.

Carcinoma, Hepatocellular↗
PubMed1985

Asthma mortality.

Explore the source record for details and available documents.

Adolescent↗
PubMed1985

Research in fire prevention.

This paper describes in broad terms, the fire testing programme we carried out on whole bed assemblies in 1984. It should be clear that the tests were carried out in a thoroughly rigorous scientific manner. As always there is more to be done. The immediate task of finding the so called 'safe' bed assembly is proceeding with the search this year for safer pillows. Softer barrier foams are now being produced and it may be that the NHS could use full depth foam mattresses rather than a barrier foam wrap. On the engineering side I have explained the false alarm problem, and I have reviewed some of the research we are doing to see that new technology is used to give us better systems in future. Life safety sprinkler systems give the possibility of truly active fire protection in patient areas. They will enhance fire safety but at the moment no trade-offs can be offered in other areas of fire protection--either active or passive. My final point is that although I have considered the Department's fire research by looking separately at specific projects, the fire safety of a hospital must always be considered as a total package. To be effective, individual components of fire safety must not be considered in isolation but as part of the overall fire safety system.

Beds↗