Epidemiology
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Chlorination of drinking water that contains organic compounds leads to the formation of by-products, some of which have been shown to have mutagenic or carcinogenic effects. As yet, too little is known about the possible teratogenic effects on the human fetus. We linked the Norwegian waterwork registry, containing 1994 data on chlorination practice and color (an indicator for natural organic matter), with the Medical Birth Registry for 1993-1995. ⋯ Among 141,077 births, 2,608 (1.8%) had birth defects. In a comparison between exposed (high color; chlorination) and reference groups (low color; no chlorination), the adjusted odds ratio was 1.14 (0.99-1.31) for any malformation, 1.26 (0.61-2.62) for neural tube defects, and 1.99 (1.10-3.57) for urinary tract defects. This study provides further evidence of the role of chlorination of humic water as a potential cause of birth defects, in a country with relatively low levels of chlorination byproducts.
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We assessed the impact of smoking cessation on subsequent death rates among a cohort of 51,343 men and 66,751 women in California enrolled in late 1959 in the original American Cancer Society (ACS) Cancer Prevention Study (CPS I) and followed for 38 years. We compared the age-adjusted death rate, expressed as deaths per 1,000 person-years, among all subjects who smoked cigarettes in 1959 but who had largely quit as of 1997 with the death rate among never smokers over a 38-year period. The all causes death rate for males decreased from 20.67 during 1960-1969 to 18.68 during 1960-1997 for smokers and decreased from 10.51 to 9.46 for never smokers. ⋯ The lung cancer death rate for females increased greatly from 0.208 to 0.806 for smokers and increased from 0.094 to 0.116 for never smokers. These results indicate there has been no important decline in either the absolute or relative death rates from all causes and lung cancer for cigarette smokers as a whole compared with never smokers in this large cohort, in spite of a substantial degree of smoking cessation. While cessation clearly reduces the mortality risk among long-term former smokers, the population impact of cessation appears to be less than currently believed.
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Ten large European cities provided data on daily air pollution as well as mortality from respiratory and cardiovascular mortality. We used Poisson autoregressive models that controlled for trend, season, influenza epidemics, and meteorologic influences to assess the short-term effects of air pollution at each city. We then compared and pooled the city-specific results in a meta-analysis. ⋯ Eight-hour averages of ozone were also moderately associated with daily mortality in western European cities (relative risk = 1.02; 95% CI = 1.00-1.03 for cardiovascular conditions and relative risk = 1.06; 95% CI = 1.02-1.10 for respiratory conditions). Nitrogen dioxide did not show consistent relations with daily mortality. These results are similar to previously published data and add credence to the causal interpretation of these associations at levels of air pollution close to or lower than current European standards.
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To examine the relation between family history of breast cancer in a mother or sister and a man's risk of fatal prostate cancer, we analyzed data from a prospective mortality study of adult men in the United States. During 12 years of follow-up, there were 3,141 deaths from prostate cancer in a cohort of 480,802 men who were cancer-free at study entry in 1982. ⋯ The association was stronger among men younger than 65 years of age whose relatives were diagnosed with breast cancer before age 50 years (RR = 1.65; 95% CI = 0.88-3.10) and among Jewish men (RR = 1.73; 95% CI = 1.00-2.97). The increased risks observed in these subgroups may reflect genetic alterations underlying familial clustering of prostate and breast cancer.