PubMed Health⌕ Search

Biomedical subjects

H Checkoway

Publications and source records attributed to H Checkoway.

At least 91 records · Page 5Linked to original sources
PubMed1987

A case-control study of skin cancer in the tire and rubber manufacturing industry.

A case-control study was conducted in the tire and rubber manufacturing industry to examine the association of squamous cell carcinoma of the skin with rubber manufacturing materials presumed to be contaminated by polycyclic aromatic hydrocarbons. Sixty-five cases were compared to 254 matched controls for exposure to carbon black, extender oils, lubricating oils, rubber solvents, and rubber stock. Both magnitude and duration of exposure were compared using data from company personnel records. Rubber stock and lubricating oils were associated with skin cancer. The relative risk (RR) associated with the highest levels of rubber stock exposure was 2.2, and with the highest level of lubricating oil exposure it was 6.5. In analysis of subgroups of study members, the associations were strongest among workers who were born after 1900 (rubber stock, RR = 11.6; lubricating oil, RR = 4.5) and among workers whose skin cancer was diagnosed before the age of seventy (rubber stock, RR = 23.2; lubricating oil, RR = 28.3).

Adult↗
PubMed1987

Medical, life-style, and occupational risk factors for prostate cancer.

Information on suspected risk factors for prostate cancer was obtained from in-person interviews as part of a case-control study of tissue sex hormone receptors and serum hormone levels. The risk factors examined were medical history (including venereal disease), sexual history, smoking, alcohol consumption, and occupational exposures. Study subjects were 40 prostate cancer patients and 64 benign prostatic hyperplasia controls who were newly diagnosed during 1984-1985 at North Carolina Memorial Hospital in Chapel Hill. Subjects were white and black men aged 50 years and older. Comparisons of cases' and controls' past medical histories did not support a venereal disease hypothesis of prostate cancer etiology. The most prominent finding is an association with farming employment: 75% of cases compared to 38% of controls reported farmwork occupations. Exposures to pesticides and herbicides, while more common among the patients, did not account for the association detected for farming. No relationship was observed with cadmium exposure, the most frequently cited occupational risk factor for prostate cancer.

Adenocarcinoma↗
PubMed1987

Androgen receptors detected by autoradiography in prostatic carcinoma and benign prostatic hyperplastic tissue.

Androgen receptor (AR) content in prostatic tissues from patients with either cancer or benign prostatic hyperplasia (BPH) is of interest from at least two standpoints: receptors may be a feature of the pathogenesis of these conditions, and they may be important to the management and prognosis of prostatic cancer patients. For these reasons, a quantitative autoradiographic assay for AR content in prostatic tissues has been developed. Application of autoradiography to rodent tissues yielded results that were highly correlated with those from biochemical assays. Thus, the autoradiographic analyses with human tissues reported in this paper were undertaken. Average AR content in 22 prostatic carcinomas was lower than that in tissues from 14 patients with BPH; the median values of the affinity index, the quantitative estimate of receptor content, were 7.0 and 12.0, respectively. For the cancer tissues, a trend of declining receptor content with advancing stage of disease appeared but was not statistically significant. No association between receptor content and degree of tumor aggressiveness as measured by Gleason score and MD Anderson score was evident. Patient age and race were not related to receptor content in either type of tissue.

Aged↗
PubMed1987

Serum hormone levels among patients with prostatic carcinoma or benign prostatic hyperplasia and clinic controls.

This study sought to identify differences in serum hormone levels between prostatic cancer (CaP) patients, benign prostatic hyperplasia (BPH) patients, and clinic controls (CC). Serum testosterone, estradiol, and prolactin values were obtained from 35 CaP, 42 BPH, and 161 CC patients attending a single medical center between January 1984 and April 1985. Relative risk estimates adjusted for age and race were calculated to compare hormone values between each case group and the CC. The distributions of hormone values and the testosterone to estradiol (T/E) ratios were grouped into thirds with the lowest third forming the reference category. The relative risk estimates for BPH in the middle and high thirds of testosterone were greater than unity (1.26 and 2.10, respectively), whereas the relative risk estimates in the middle and high thirds of estradiol were less than unity (0.63 and 0.35, respectively). For the middle and high thirds of the T/E ratio, the relative risk estimates for BPH showed statistically significant three- to fourfold increases. Modest depression of serum testosterone and estradiol was noted for CaP patients compared to CC, although the differences were not statistically significant. This depression was interpreted to be a likely result of the malignant process rather than a cause of it, whereas the development of clinically evident BPH was felt to be a biologically plausible response to an elevated T/E ratio.

Age Factors↗
PubMed1987

Metabolic modeling of organ-specific doses to carcinogens as illustrated with alpha-radiation emitting radionuclides.

Quantitative estimation of doses of carcinogens delivered to physiologic targets facilities specification of organ-specific dose-response functions. Typically, exposure measurements, such as air or water concentrations of carcinogens, are used as dose surrogates in epidemiologic studies. An illustrative exception to this usual situation is the case of airborne alpha radiation-emitting radionuclides, for which organ-specific doses can be derived. A metabolic modeling approach for estimating doses delivered to the lung, gastrointestinal tract and bone is described for three classes of radionuclides: soluble uranium, insoluble uranium and plutonium. The dose models are defined in terms of biological retention patterns and organ-specific depositions affinities. Application of the metabolic modeling approach is illustrated with a hypothetical example of excess lung cancer risk projection in a cohort of persons exposed to plutonium. Also, a simple example is presented to demonstrate how adherence to the metabolic model structure can avoid gross overestimation of doses in the case of multiple in vivo lung counting measurements taken in close temporal proximity following a large exposure intake.

Dose-Response Relationship, Radiation↗
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↗
PubMed1986

Ocular sarcoidosis. A case-control study among black patients.

A case-control study was conducted to investigate possible environmental risk factors for ocular sarcoidosis. The factors studied were exposures to pine products and occupational histories of employment in the tobacco, lumber, and textile industries. The exposure histories of 29 female and 15 male cases, patients with newly diagnosed ocular sarcoidosis that were attending the Glaucoma/Uveitis Clinic of the North Carolina Memorial Hospital, were compared to those of 110 female and 28 male controls selected from out-patient clinics. Elevated risks for sarcoidosis were detected among those females that were exposed to burning pine or were employed in the tobacco industry. For males, positive associations were observed for chewing pine products and for employment in the lumber and textile industries. These preliminary data are consistent with incomplete phagocytic clearance of nonbiodegradable foreign bodies present within our environment that may become antigenic to the immunologically susceptible host. Confirmation of refutation of these hypotheses awaits additional clinical and epidemiological research within the sarcoidosis belt.

Adolescent↗
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

Epidemiologic programs for computers and calculators. Use of Poisson regression models in estimating incidence rates and ratios.

Summarizing relative risk estimates across strata of a covariate is commonly done in comparative epidemiologic studies of incidence or mortality. Conventional Mantel-Haenszel and rate standardization techniques used for this purpose are strictly suitable only when there is no interaction between relative risk and the covariate, and tests for interaction typically are limited to examination for departures from linearity. Poisson regression modeling offers an alternative technique which can be used for summarizing relative risk and for evaluating complex interactions with covariates. A more general application of Poisson regression is its utility in modeling disease rates according to postulated etiologic mechanisms of exposures or according to disease expression characteristics in the population. The applications of Poisson regression analysis to problems of summarizing relative risk and disease rate modeling are illustrated with examples of cancer incidence and mortality data, including an example of a nonlinear model predicted by the multistage theory of carcinogenesis.

Adolescent↗
PubMed1985

Radiation, work experience, and cause specific mortality among workers at an energy research laboratory.

A retrospective cohort mortality study was conducted among 8375 white male employees who had worked at the Oak Ridge National Laboratory for at least one month between 1943 and 1972. This plant has been the site of energy related research, including uranium and plutonium reactor technology and radioisotope production. Radiation doses, primarily from gamma rays, were generally low; the median cumulative exposure for workers was 0.16 rems. Historical follow up was conducted for the years 1943-77 and ascertainment of vital status was achieved for 92.3% of the cohort. Standardised mortality ratios (SMRs) were computed to contrast the subjects' cause specific mortality experience with that of the United States white male population. The observed number of 966 deaths from all causes was 73% of the number expected. Mortality deficits were also seen for arteriosclerotic heart disease (SMR = 0.75; 344 observed) and all cancers (SMR = 0.78; 194 observed). These results are indicative of the healthy worker effect and the favourable influence on health of the cohort's relatively high socioeconomic status. Non-statistically significant raised SMRs were seen for all leukaemias (SMR = 1.49, 16 observed), cancer of the prostate (SMR = 1.16, 14 observed), and Hodgkin's disease (SMR = 1.10, 5 observed). Internal comparisons of mortality (standardised rate ratios, SRRs) were made between subgroups of the cohort according to radiation dose level and duration of employment in various job categories. No consistent gradients of cause specific mortality were detected for radiation exposure. Leukaemia mortality was highest among workers with greater than or equal to 10 years employment in engineering (SRR = 2.40) and maintenance (SRR = 3.12) jobs. The association of leukaemia with employment in engineering was unexpected; maintenance jobs entail potential exposures to radiation and to a wide range of organic chemicals; metals, and other substances.

Adolescent↗
PubMed1985

Assessing the possible extent of confounding in occupational case-referent studies.

Case-referent studies nested within occupational cohort studies are efficient designs for estimating relative risks associated with exposures and for obtaining data on nonoccupational confounding factors. Frequently, however, only incomplete data on confounders can be obtained from sources such as next-of-kin or co-workers. A method for assessing the potential extent of confounding in cohort studies described previously by Axelson [Scand J Work Environ Health 4 (1978) 98-102] can be adapted for use in nested case-referent studies. An example is shown to illustrate that the adapted Axelson method is preferable to the usual confounder adjustment techniques when data on the confounder are incomplete.

Epidemiologic Methods↗
PubMed1985

Mortality among workers in the Florida phosphate industry. I. Industry-wide cause-specific mortality patterns.

A retrospective cohort mortality study was conducted on 17,601 white and 4,722 nonwhite male workers in the Florida phosphate mining and chemical processing industry. Concerns about potential risks from naturally-occurring sources of ionizing radiation and anecdotal reports of lung cancer among workers prompted this investigation. Historical follow-up was conducted for the years 1949 to 1978. In comparison with U.S. rates, small excess of mortality rates of lung cancer were observed for white (standardized mortality ratio [SMR] equals 1.22) and nonwhite workers (SMR = 1.24); however, these excesses disappeared when contrasts were made with prevailing rates in Florida. Emphysema mortality was also slightly elevated in comparison with U.S. rates; the SMRs were 1.48 and 1.73 for white and nonwhite workers, respectively. Neither disease was related to overall length of employment. Detailed analyses of mortality in relation to work assignments are presented in the companion article.

Adult↗
PubMed1985

Mortality among workers in the Florida phosphate industry. II. Cause-specific mortality relationships with work areas and exposures.

Small excesses of lung cancer and emphysema mortality had been detected among an historical cohort of 17,601 white and 4,722 nonwhite Florida phosphate industry workers. Internal mortality rate comparisons were made between worker subcohorts classified according to length of employment in 16 work areas and according to employment duration in jobs grouped by potential exposures to 10 agents, including alpha radiation. The only consistent associations seen were increased lung cancer mortality rates among long-term workers in plant-wide services and skilled crafts jobs. There was no evidence to support causal associations with exposures characteristic of the phosphate industry.

Adult↗
PubMed1984

An evaluation of the associations of leukemia and rubber industry solvent exposures.

Excessive leukemia mortality has appeared consistently in epidemiological studies of British and U.S. rubber industry workers. Attempts to identify causative factors have focused on exposure to benzene and other solvents. Interpretations of findings from these studies have often been influenced by expectations of a benzene/nonlymphocytic leukemia association, seen from previous work in other settings. However, data from the rubber industry studies have not been consistent with this expectation, as lymphocytic and nonlymphocytic leukemia have shown similar mortality excesses. Data from a small case-control study of lymphocytic leukemia are presented to illustrate an approach that considers multiple solvent exposures. The associations with lymphocytic leukemia risk observed for a number of solvents, most notably carbon tetrachloride and carbon disulfide, were stronger than those detected for benzene.

Adult↗
PubMed1984

Cancer mortality and solvent exposures in the rubber industry.

Some evidence suggests that solvent exposures to rubber industry workers may be associated with excess cancer mortality, but most studies of rubber workers lack information about specific chemical exposures. In one large rubber and tire-manufacturing plant, however, historical documents allowed a classification of jobs based on potential exposures to all solvents that were authorized for use in the plant. A case-control analysis of a 6678 member cohort compared the solvent exposure histories of a 20% age-stratified random sample of the cohort with those of cohort members who died during 1964-1973 from stomach cancer, respiratory system cancer, prostate cancer, lymphosarcoma, or lymphatic leukemia. Of these cancers, only lymphosarcoma and lymphatic leukemia showed significant positive associations with any of the potential solvent exposures. Lymphatic leukemia was especially strongly related to carbon tetrachloride (OR = 15.3, p less than .0001) and carbon disulfide (OR = 8.9, p = .0003). Lymphosarcoma showed similar, but weaker, associations with these two solvents. Benzene, a suspected carcinogen, was not significantly associated with any of the cancers.

Adult↗
PubMed1983

Lymphocytic leukemia and exposures to benzene and other solvents in the rubber industry.

Previous epidemiological studies on one cohort of rubber industry workers indicated that observed mortality excesses from lymphocytic leukemia were related to solvent exposures. The results of a detailed examination of the solvent exposure histories of 15 cases of lymphocytic leukemia from this cohort and 30 matched industry controls are presented. Extensive review of historical solvent use, raw materials specifications and job description records were used to reconstruct exposures to specific agents. Cases were 4.5 times as likely as controls to have had direct exposures to both benzene and other solvents. Analysis by manufacturing production source of solvent revealed that cases spent greater proportions of their work experience in jobs with potential exposures to coal tar-based benzene and xylene. No differences were seen for petroleum-derived solvents.

Adult↗