ABSTRACT
As a nonparametric method,the Kruskal-Wallis test is widely used to compare three or more independent groups when an ordinal or interval level of data is available,especially when the assumptions of analysis of variance (ANOVA) are not met.If the Kruskal-Wallis statistic is statistically significant,Nemenyi test is an alternative method for further pairwise multiple comparisons to locate the source of significance.Unfortunately,most popular statistical packages do not integrate the Nemenyi test,which is not easy to be calculated by hand.We described the theory and applications of the Kruskal-Wallis and Nemenyi tests,and presented a flexible SAS macro to implement the two tests.The SAS macro was demonstrated by two examples from our cohort study in occupational epidemiology.It provides a useful tool for SAS users to test the differences among three or more independent groups using a nonparametric method.
ABSTRACT
To investigate the health impacts of crystalline silica mixed dust and other potential occupational hazards on workers in ceramic factories, a cohort study of 4851 workers registered in the employment records in 3 ceramic factories in Jingdezhen city of China between 1972 and 1974 was identified2 The cohort mortality was traced throughout 2003 with an accumulation of 128970.2 person-years, revealed 1542 deaths. Standardized mortality ratios (SMRs) were calculated for the main causes of death by using Chinese national mortality rates as reference. The mortality from all causesin three ceramic factories was 12.0‰ and the cumulative mortality was 31.8%. Malignant neoplasm,cardiovascular diseases, respiratory diseases, infectious diseases were the first four illnesses that threaten workers' life, and they accounted for 73.2% of all deaths. The resultsof this study showed that the standardized mortality ratio for all subjects was 1.02, which is very close to that expected on the basis of the China national mortality rates. Statistically significant mortality excesses for respiratory disease (SMR=1.36), pneumoconiosis (SMR=37.34), infectious disease (SMR=5.70) and pulmonary tuberculosis (SMR=3.88) were observed. The mortality of 2938 dust-exposed workers was higher than that of 1913 non dust-exposed workers. Except for pneumoconiosis, the mortality from lung cancer, non-malignant respiratory diseases and pulmonary tuberculosis in dust-exposed workerswere significantly increased as compared with that in non-exposed workers, and the relative risks(RRs) were 1.86 (1.16-2.99), 2.50 (1.84-3.40), 1.81 (1.34-2.45). The exposure-response relationships between cumulative dust exposure level and mortality from all causes, colorectal cancer, lung cancer, respiratory diseases, and pulmonary tuberculosis were also identified. The findings indicatedthat silica mixed dust in ceramic factories has harmful impact on the workers' health and life span in ceramic factory.
ABSTRACT
Summary: The influence of exercise at high temperature on adult males' routine blood indexes and biochemical indexes and the expression of HSP72 in peripheral blood lymphocytes (PBLs) was studied in order to provide theoretical ground for health supervision of adults receiving exercise at high temperature. 180 adult males were selected and divided into exercise group and control group, in which the exercise group was subdivided into subgroup 1 and subgroup 2 receiving exercise at high temperature in the afternoon and in the morning, respectively. Peripheral venous blood was phlebotomized before and after the exercise to examine routine blood indexes and blood biochemical indexes. The expression levels of HSP72 in PBLs were detected by flow cytometry. The results showed that the routine blood indexes and biochemical indexes in each group were within the range of normal values of male adults. There was no significant difference between each exercise group and control group in indexes before exercise. After exercise, the expression levels of HSP72 in PBLs in exercise groups were higher than those before exercise, and HSP72 expression levels'in subgroup 1 were obviously higher than those in subgroup 2 and control group. The contents of ALT, urea, Na+, Cl-, Ca2+and K+ in subgroups 1 and 2 were lower than those in control group, but CK level was higher than in control group (P<0.05). The contents of Na+ and Cl- in subgroup 1 were relatively lower than those in subgroup 2 (P<0.05). It was concluded that while receiving exercise at high temperature, adult males' HSP72 levels in PBLs could be increased and the biochemical indexes changed. Attention should be paid to health supervision to avoid obvious body injuries at high temperature.