Markku Nurminen

In this paper, we examine comparative analysis of rates with a view to each of the usual comparative parameters-rate difference (RD), rate ratio (RR) and odds ratio (OR)-and with particular reference to first principles. For RD and RR we show the prevailing statistical practices to be rather poor. We stress the need for restricted estimation of variance in the chi-square function underlying interval estimation (and also point estimation and hypothesis testing). For RR analysis we propose a chi-square formulation analogous to that for RD and, thus, one which obviates the present practice of log transformation and its associated use of Taylor series approximation of the variance. As for OR analysis, we emphasize that the chi-square function, introduced by Cornfield for unstratified data, and extended by Gart to the case of stratified analysis, is based on the efficient score and thus embodies its optimality properties. We provide simulation results to evince the better performance of the proposed (parameter-constrained) procedures over the traditional ones.

OBJECTIVES: This study attempts to estimate the proportion of annual deaths related to occupational factors in Finland and considers related methodological issues and associated uncertainties. METHODS: Statistics on causes of death, numbers of subjects exposed, and risk ratios obtained from the epidemiologic literature were used to estimate the population attributable fraction and disease burden for causes of death from work-related diseases. Gender-, age- and disease-specific numbers of deaths were provided by Statistics Finland for 1996. Information on the size of the population, broken down by gender, age, occupation, and industry, was acquired from population censuses. A Finnish job-exposure matrix supplied data on the prevalence of exposure for specific agents and the level of exposure among exposed workers. RESULTS: The attributable fraction of work-related mortality in the relevant disease and age categories was estimated to be 7% (10% for men and 2% for women), and for all diseases and ages the fraction was 4%. For the main cause-of-death categories, the attributable fraction became 12% for circulatory system diseases, 8% for malignant neoplasms, 4% for respiratory system diseases, 4% for mental disorders, 3% for nervous system diseases, and 3% for accidents and violence. The following estimates were obtained for specific important diseases: 24% for lung cancer, 17% for ischemic heart disease, 12% for chronic obstructive pulmonary disease, and 11% for stroke. Based on these fractions, the total number of work-related deaths that occurred in Finland in 1996 was calculated to be on the order of 1800 (employed work force of 2.1 million); 86% involved men. CONCLUSIONS: High-quality epidemiologic studies and national survey data are essential for obtaining reliable estimates of the proportion of deaths attributable to occupational factors. The magnitude of work-related mortality is an insufficiently recognized contributor to total mortality in Finland, especially from circulatory diseases and other diseases caused by exposure to agents other than asbestos.

The behavioral effects of long-term exposure to a mixture of organic solvents were investigated in a comparison of the test results of 100 car painters with those of a reference group. The test battery included tests for intelligence, memory, psychomotor performances, and personality. In addition to the comparison of the mean results, two discriminant function analyses were made. In one, only the performance test variables were used, but in the other personality variables were also included. The results indicated impairments in psychological performances, as well as personality changes in the exposed group. Impairments in visual intelligence and verbal memory and a reduction of emotional reactivity were the central features of the adverse effects of solvent exposure, but the behavioral disturbances also involved several other functions, including performance on a verbal intelligence test. The possible role of the differences in the initial intelligence levels were controlled with a separate comparison of the test results of 33 pairs of exposed and nonexposed subjects who were matched for age and for their intelligence level, measured during the military service. The discriminant function analyses were based on the results of these matched subgroups and tested in the rest of the material. According to the results the sensitivity of the psychological test methods was high, but the specificity somewhat low, with regard to solvent exposure. The concentration of various solvents included in the exposure of car painters were low, the summated exposure corresponding corresponding to 32% of the Finnish threshold limit value. The possible role of a potentiating effect of the solvent in the development of behavioral disturbances is discussed.

The occurrence of symmetric disc degeneration, anular ruptures, end-plate defects, vertebral body osteophytosis, and facet joint osteoarthrosis was examined radiographically and osteologically in 86 male cadavers for whom occupational, physical loading, and back pain histories were obtained from the men's families. History of back pain and the parameters of spinal pathology were related to the highest and lowest degrees of physical loading. In multivariate analyses, history of back injury was related to the occurrence of symmetric disc degeneration, anular ruptures, and vertebral osteophytosis. Symmetric disc degeneration was associated with sedentary work, and vertebral osteophytosis was related to heavy work. History of back pain was related to occupational physical loading after control for the effects of the other covariates. The results indicate that the least pathology stemmed from moderate or mixed physical loading, but the least back pain was associated with sedentary work.