Showing papers by "Neil Pearce published in 1986"

Non-Hodgkin's lymphoma and exposure to phenoxyherbicides, chlorophenols, fencing work, and meat works employment: a case-control study.

Abstract: A previous case-control study which used the occupational information available on the New Zealand Cancer Registry found that agricultural workers were at increased risk of developing non-Hodgkin's lymphoma. The findings are now presented for the second phase of the study which entailed interviewing 83 cases of non-Hodgkin's lymphoma registered under code 202 of the International Classification of Diseases together with 168 controls with other types of cancer and 228 general population controls. The findings for the two control groups were similar, and there were no significant differences between cases and controls regarding potential exposure to phenoxy-herbicides (odds ratio = 1.4, 90% confidence limits 0.7-2.5, p = 0.26) or chlorophenols (odds ratio = 1.3, 90% confidence limits 0.6-2.7, p = 0.39). The odds ratio for fencing work, necessitating exposure to several potential risk factors including arsenic and sodium pentachlorophenate was 2.0 (90% confidence limits 1.3-3.0, p = 0.01). The odds ratio for employment in a meat works, necessitating potential exposure to 2, 4, 6-trichlorophenol and zoonotic viruses, was 1.8 (90% confidence limits 1.1-3.1, p = 0.04). There was a significant statistical interaction between the risks associated with these two activities, the odds ratio for involvement in both activities compared with involvement in neither being 5.7 (90% confidence limits 2.3-14.3, p = 0.03).

Case-control study of multiple myeloma and farming.

Abstract: A previous case-control study which utilised the occupational information available on the New Zealand Cancer Registry found an increased risk of multiple myeloma in agricultural workers consistent with previous findings in the United States. The findings are now presented for the second phase of the study which involved interviewing 76 cases of multiple myeloma (who had been included in the previous study) together with 315 controls with other types of cancer. The previous finding on an excess of farmers in the case group was confirmed by the interview data (odds ratio = 1.7, 95% confidence limits 1.0-2.9, P = 0.04). There were no significant differences between cases and controls regarding potential exposure to phenoxy herbicides or chlorophenols. There were also no significant differences regarding activities involving potential exposure to other agricultural chemicals, although the odds ratio for fencing work, which may involve exposure to arsenic and sodium pentachlorophenate, was 1.6 (95% confidence limits 0.9-2.7, P = 0.11). The odds ratios were significantly elevated for sheep farming (odds ratio = 1.9, 95% confidence limits 1.0-3.6, P = 0.04) and exposure to beef cattle (odds ratio = 1.7, 95% confidence limits 1.0-2.9, P = 0.05). The odds ratio was also elevated for persons reporting a history of hay fever (odds ratio = 1.9, 95% confidence limits 1.0-3.5, P = 0.05). Overall, these findings suggest that the search for the causes of elevated mortality in farmers from multiple myeloma should be directed to potential causes other than pesticide exposure.

Occupation social class and male cancer mortality in New Zealand 1974-78.

Abstract: Occupational and social class differences in cancer mortality among New Zealand males aged 15-64 are examined for the period 1974-78. Age-standardized cancer mortality rates are presented for the Registrar Generals social classes as well as for each of six occupational orders and 79 occupational groups. The rates for specific cancer sites are also presented for each social class and for those occupational groups with significantly elevated relative risks. The findings of the social class analyses are generally consistent with those of recent British studies "with mortality from cancer of the liver larynx lung buccal cavity and stomach being particularly high in the lower social classes and mortality from multiple myeloma malignant melanoma and lymphatic leukaemia being particularly high in the upper social classes." (EXCERPT)

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

Abstract: 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.

Leukemia among new zealand agricultural workers a cancer registry-based study

Abstract: Mortality studies have indicated that workers in agriculture and forestry may be at increased risk of leukemia. Findings are reported from a New Zealand Cancer Registry-based case-control study involving 546 male leukemia patients registered during 1979-1983 and aged 20 years or more at time of registration. Controls were also males chosen from the Cancer Registry with four controls per case, matched on age and year of registration. The case group contained an excess of the occupational category involving agriculture and forestry (odds ratio (OR) = 1.24, 95% confidence interval (CI) = 0.95-1.61) with the greatest relative risk being for livestock farmers (OR = 3.00, 95% CI = 1.23-7.32). There was also an excess of electrical workers (OR = 1.72, 95% CI = 0.92-3.20). The agricultural excess was greatest in patients aged 65 years or more at time of registration (OR = 1.29, 95% CI = 0.94-1.78), particularly in patients with acute myeloid leukemia (OR = 1.55, 95% CI = 0.90-2.67) or acute monocytic leukemia OR = 10.38, 95% CI = 1.99-54.29), although the latter excess only involved five cases. Acute myeloid leukemia was also elevated in meat workers (OR = 2.51, 95% CI = 1.19-5.30).

Low dose hepatitis B vaccination in children.

Abstract: One hundred and sixty-nine children negative for hepatitis B surface antigen (HBsAg) and antibody (anti-HBs), were given three doses of hepatitis B vaccine at monthly intervals. Doses were two micrograms or four micrograms given intradermally (ID) or intramuscularly (IM). All children were tested for HBsAg, anti-HBs and antibody to hepatitis B core antigen (anti-HBc) one month after the second dose of vaccine. Overall, 74% of children on two micrograms doses and 71% of children on four micrograms doses responded to two doses of vaccine by the production of anti-HBs. At this point, mass immunisation of other susceptible children was commenced. Four of 92 (4%) three to five year old subjects and 20 of 77 (26%) nine to 12 year olds were found to be anti-HBc positive alone, indicating prior infection. All 77 older children were further tested two months after the third dose of vaccine. All 20 who were anti-HBc positive, sero-converted for anti-HBs. Of the remaining 57, 52 (91%) produced anti-HBs at acceptable geometric mean titres (GMT). Three doses of two micrograms of H-B-VAX, given at monthly intervals were chosen for mass vaccination of high risk susceptible children in this mobile community, providing over 90% sero-conversion at low cost with a minimum of side effects.

Analysis of the components of a linear trend in proportions

Abstract: The standard epidemiologic methods for evaluating trends in the prevalence or incidence of disease are reviewed, and a method is presented for assessing the contribution of a specific disease subgroup to the overall trend, based on the slope obtained by a grouped weighted linear regression of the proportions of persons experiencing the outcome of interest in each exposure level. The slopes for specific disease subgroups contribute to the overall slope in an additive manner, and measures based on the individual slopes can be used to assess the relative strengths of the trends for specific disease subgroups as well as their relative contributions to the overall trend. This approach is illustrated with data on social class patterns of mortality in New Zealand males aged 15-64 years during 1974-1978; it is shown that the strongest mortality gradients were for mental disorders, infectious diseases, respiratory diseases, and accidents. The latter two categories together accounted for approximately two thirds of the overall social class mortality gradient.