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Biomedical subjects

N Pearce

Publications and source records attributed to N Pearce.

At least 73 records · Page 4Linked to original sources
PubMed1989

Prescribed fenoterol and death from asthma in New Zealand, 1981-83: case-control study.

A case-control study was conducted to examine the hypothesis that fenoterol by metered dose inhaler (MDI) increases the risk of death in patients with asthma. The case group comprised 117 patients aged 5-45 who died of asthma between August, 1981, and July, 1983. For each case, 4 controls, matched for age and ethnic group, were selected from asthma admissions to hospitals to which the cases themselves would have been admitted, had they survived. The relative risk of asthma death in patients prescribed fenoterol by MDI was 1.55 (95% CI 1.04-2.33, p = 0.03). The possibility of confounding or effect modification by severity was assessed by consideration of subgroups defined by markers of asthma severity. The fenoterol MDI relative risk was 2.21 (95% CI 1.26-3.88, p = 0.01) in patients prescribed three or more categories of asthma drugs, 2.16 (95% CI 1.14-4.11, p = 0.02) in patients with a hospital admission for asthma during the previous 12 months, and 6.45 (95% CI 2.72-15.3, p less than 0.01) in patients prescribed oral corticosteroids at time of death or admission. In the group of patients with the most severe asthma (defined by a hospital admission during the previous year and prescription of oral corticosteroids) the fenoterol MDI relative risk was 13.29 (95% CI 3.45-51.2, p less than 0.01). After adjustment for severity, no other asthma treatment commonly used in New Zealand seemed to be associated with an increased risk of asthma death. Not all sources of bias can be definitely excluded; however, when considered together with other epidemiological and experimental evidence, these findings are consistent with the hypothesis that use of fenoterol by MDI increases the risk of death in severe asthma.

Acute Disease↗
PubMed1989

Soft-tissue sarcoma, non-Hodgkin's lymphoma and other cancers in New Zealand forestry workers.

Several studies have suggested that forestry workers are at increased risk for certain types of cancer including soft-tissue sarcoma (STS) and non-Hodgkin's lymphoma (NHL). We now report a series of national case-control studies based on the New Zealand Cancer Registry (NZCR). These involved 19,904 male patients with cancer for the period 1980-1984 who were aged 20 years or more at the time of registration. For each cancer site, the registrations for the remaining sites formed the control group. Current or most recent occupational titles were coded. There was an increased risk for STS (OR = 3.24) in forestry workers which was confined to men under 60 years of age at registration. An elevation in risk for NHL (OR = 1.84) was due to an increase in risk for lymphosarcoma and reticulosarcoma (ICD 200) (OR = 3.18). Acute myeloid leukemia was also associated with forestry work, although the estimate of risk was imprecise (OR = 2.24). Among other cancer sites, an increase in risk of neoplasia of the upper gastro-intestinal tract (ICD 150, 151, 152) was demonstrated. Odds ratios were elevated for cancer of the esophagus (OR = 1.77), stomach (OR = 2.22), small intestine (OR = 5.22), gall-bladder (OR = 4.13) and pancreas (OR = 1.79), as well as for nasopharyngeal cancer (OR = 5.56). These increases in cancer risk were not present in sawmill workers in New Zealand during the same period. The factors responsible for the increased cancer risks in forestry workers remain unclear and require further study.

Adult↗
PubMed1989

Design and conduct of occupational epidemiology studies: I. Design aspects of cohort studies.

Cohort and case-control studies are two standard approaches for investigating the etiology of occupational diseases. This paper, which is the first of a four-part series, contains a review of the design features of occupational cohort studies. Topics discussed include the basic features of prospective and historical cohort studies, options for defining the cohort, disease incidence ascertainment, and considerations involved in planning an occupational cohort study. Subsequent papers in this series will focus on data analysis of occupational cohort studies and the design and analysis of occupational case-control studies.

Cohort Studies↗
PubMed1989

Design and conduct of occupational epidemiology studies: II. Analysis of cohort data.

This paper reviews strategies and statistical methods for analyzing data from occupational cohort studies. Emphasis is placed on the common methods for grouped data analysis involving external and internal comparison populations. Analysis procedures reviewed are standardized mortality ratio, standardized rate ratio, and Mantel-Haenszel techniques for estimating relative risks. Methods for control of confounding, assessment of effect modification, and allowance for disease latency are discussed. These concepts and procedures are illustrated with data from an historical cohort mortality study of workers from an asbestos textile plant.

Biometry↗
PubMed1989

Design and conduct of occupational epidemiology studies: III. Design aspects of case-control studies.

Currently available approaches for the design of occupational case-control studies are reviewed. An accompanying paper reviews methods of analysis. We commence by drawing a distinction between cohort-based and registry-based studies. Methods for selecting cases and controls are then reviewed, including cumulative incidence and incidence density sampling, matching, sources of controls, and issues in control selection. Finally, the advantages and disadvantages of the case-control approach are summarized.

Cohort Studies↗
PubMed1989

Design and conduct of occupational epidemiology studies: IV. The analysis of case-control data.

This paper reviews the basic methods of analysis of data from case-control studies. The standard analytic methods are outlined first for a single stratum. The discussion is then extended to stratified analysis, multiple exposure levels, and analyses allowing for disease induction and latency periods. Finally, logistic regression is discussed as an extension of the more basic forms of analysis. The methods are illustrated with data from a study of lung cancer among asbestos textile plant workers.

Biometry↗
PubMed1989

Critical discussion in epidemiology: problems with the Popperian approach.

There has been a renewed interest in the philosophical and scientific basis of epidemiology in recent years. In particular, it has been argued that Popper's philosophy should be adopted by epidemiologists, an assertion that has met with some scepticism. However, most criticisms of Popper's approach have been from an inductivist viewpoint, concerned with the generation of theories, whereas Popper's concern is with the testing of theories, and the two schools have been largely "talking past each other". We present a critique of Popper from within his own domain of interest. Examples are presented to show that Popper's philosophy is incomplete even for the physical sciences on which it is based, and that it is particularly inappropriate for epidemiology. Popper's approach makes sense only under the narrow way he has chosen to define science, and thus provides only a possible answer to a small set of fundamental problems of science and its use in society. The recent Popperian "trend" has a positive aspect in that it has fostered deductive thinking, and exposed the shortcomings of induction. However, the restrictive Popperian framework actually inhibits discussion despite its veneer of "critical discussion". A more pluralistic approach is needed at this stage of the development of epidemiology.

Epidemiologic Methods↗
PubMed1989

Case-control studies of cancer in New Zealand electrical workers.

A series of reports, including a New Zealand case-control study, have suggested that electrical workers are at increased risk of leukaemia. We report here a further series of case-control studies based on the New Zealand Cancer Registry. These involved 19,904 male patients registered with cancer for the period 1980-1984 who were aged 20 years or more at time of registration. For each cancer site, the registrations for other sites formed the control group. Three main findings emerged. First, there is an elevated leukaemia risk in New Zealand electrical workers (odds ratio (OR) = 1.62, 95% confidence interval (Cl) 1.04-2.52), but little evidence of increased risks for other cancer sites. Second, contrary to other published studies, the increased risk was primarily for chronic leukaemia (OR = 2.12) rather than acute leukaemia (OR = 1.25), and for lymphatic leukaemia (OR = 1.73) rather than myeloid leukaemia (OR = 1.22). Third, the increased risk was strongest for certain categories of electrical work including radio and television repairers (OR = 7.86, 95% CI 2.20-28.09), electricians (OR = 1.68, 95% Cl = 0.75-3.79), linemen (OR = 2.35, 95% Cl 0.97-5.70) and power station operators (OR = 3.89, 95% Cl 1.00-15.22).

Adult↗
PubMed1989

Cancer risks in New Zealand farmers.

Previous New Zealand case-control studies have found increased risk for leukaemia, non-Hodgkin's lymphoma (NHL) and multiple myeloma in farmers. We report here a further series of New Zealand Cancer Registry based case-control studies of farming and site-specific cancer risks. These involved 19,904 males aged 20 years or more who were registered with cancer between 1980 and 1984. For each cancer site, the registrations for other sites formed the control group. Farmers had elevated risks for malignant melanoma (Odds Ratio [OR] = 1.25, 95% confidence interval [Cl] 1.05-1.50), and for cancer of the lip (OR = 2.43, 95% Cl 1.81-3.27), rectum (OR = 1.19, 95% Cl 1.03-1.38), bone (OR = 1.95, 95% Cl 1.00-3.80), prostate (OR = 1.26, 95% Cl 1.13-1.41) and brain (OR = 1.34, 95% Cl 1.04-1.74). Decreased risks were observed for cancer of the larynx (OR = 0.66, 95% Cl 0.45-0.96), lung (OR = 0.70, 95% Cl 0.63-0.77) and testis (OR = 0.58, 95% Cl 0.39-0.88). Livestock farmers had a relatively high risk for brain cancer, while the risk for cancer of the lip was highest among dairy farmers. Farmers also had increased risks for cancer of the lymphatic and haematopoietic system (International Classification of Disease 9th edn (ICD) 200-208) (OR = 1.24, 95% Cl 1.08-1.42), leukaemia (OR = 1.24, 95% Cl 0.99-1.55) and non-Hodgkin's lymphoma (NHL) (OR = 1.24, 95% Cl 0.99-1.56), as described previously.

Adult↗
PubMed1989

Analytical implications of epidemiological concepts of interaction.

In contrast to definitions based on statistical or biological concepts, Rothman has adopted an unambiguous epidemiological definition of interaction in which two factors are not 'independent' if they are component causes in the same sufficient cause. This leads to the adoption of additivity of incidence rates as the state of 'no interaction'. However, there are other considerations which generally favour the use of multiplicative models. This implies an apparent dilemma as to how an analysis can be conducted which combines the advantages of ratio measures of effect with the assessment of independence in terms of a departure from additivity. These apparently contradictory goals can be reconciled through the analysis of separate and joint effects. This approach is discussed with reference to studies of asbestos exposure, cigarette smoking and lung cancer.

Causality↗
PubMed1989

Incidence density matching with a simple SAS computer program.

Incidence density matching is the method of choice for selecting controls in nested case-control studies, but its use has been limited by its computational complexity. We describe incidence density matching in nested case-control studies with a simple and flexible SAS computer program. The program contains no restrictions on the number of matching factors, although it is usually only necessary to match on age (in incidence density fashion) and on gender. The program is illustrated with data from an historical cohort study of the mortality experience of workers at an asbestos textile manufacturing plant.

Case-Control Studies↗
PubMed1989

Occupational risks for brain cancer: a New Zealand Cancer Registry-based study.

Occupational risks for brain cancer were evaluated in a New Zealand Cancer Registry-based case-control study. The case subjects were 452 men aged 20 years or older registered under classifications 191 (Cancer of the brain) and 192 (Cancer of other and unspecified parts of the nervous system) of the International Classification of Disease (9th ed) from 1980 to 1984 for whom occupational information was available. The remaining 19,452 men with other cancers registered during an excess of professional and technical workers. An increased risk among workers in agriculture, forestry, and fishing was due to an excess of brain cancer in farmers, with the highest risk found for livestock farmers. Although many comparisons have been made, some of the findings support previous studies and several new hypotheses are suggested.

Adult↗
PubMed1988

Hepatitis B virus: the importance of age at infection.

Recent studies have demonstrated the importance of age at infection with hepatitis B virus (HBV). Age affects whether the infection is self-limited or results in the chronic carrier state, the severity of the acute infection, and the incidence of various sequelae of the chronic carrier state. In particular, although the acute infection is more severe in adults, infections in infants and preschool children carry much greater risks of chronic carriage which increases the risk of primary hepatocellular carcinoma and cirrhosis later in life. This has two important implications for areas where HBV is endemic. First, more impact can be gained by vaccinating infants and preschool children than by vaccinating healthy adults. Second, if funds are limited, greater impact will be gained by immunising a larger number of children with low doses of vaccine so that they are protected during the early years of life when the risk of chronic carriage is highest, rather than using the standard dose in a smaller number of children even though protection may be longer lasting with standard doses. These two considerations provide the basis for an efficient strategy for control in communities or countries where HBV is endemic or hyperendemic.

Adolescent↗