PubMed · 8489943
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S Sauter. 1993. [Why do we need therapy studies?].. https://pubmed.ncbi.nlm.nih.gov/8489943/
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Adequate consumption of folate may reduce the risk of colorectal cancer. We performed a meta-analysis of 7 cohort and 9 case-control studies that examined the association between folate consumption and colorectal cancer risk. In cohort studies, the association between folate consumption and colorectal cancer risk was stronger for dietary folate (folate from foods alone; relative risk for high vs. low intake = 0.75; 95% CI = 0.64-0.89) than for total folate (folate from foods and supplements; relative risk for high vs. low intake = 0.95; 95% CI = 0.81-1.11) and there was no significant heterogeneity between studies. There was significant heterogeneity between case-control studies. These results offer some support for the hypothesis that folate has a small protective effect against colorectal cancer but confounding by other dietary factors cannot be ruled out.
The morphological analysis of the spermatozoa from fertile and infertile men was performed using light and electron microscopy to clarify the relationship between sperm morphology and fertility. Semen samples obtained from 22 partners of pregnant women were prepared according to the protocol standardized in an international collaborative study. Semen samples from 17 patients with asthenozoospermia or varicocele were collected in a hospital. Abnormalities in the spermatozoa were classified into three types for the tails, two for the midpieces, and six for the heads according to the criteria adapted from WHO guidelines (World Health Organization, 1999: WHO laboratory manual for the examination of human semen and semen-cervical mucus interaction (4th edition)). Approximately 14% of the spermatozoa from the fertile men had abnormal tails at the light microscopic level while approximately 44% had abnormal heads. Most types of abnormalities found in the spermatozoa from the asthenozoospermic and varicocele patients were encountered in those from the fertile men, although the semen from the fertile men contained a higher percentage of normal spermatozoa than that from the patients. These results were also confirmed at the ultrastructural level. Most abnormal cell types are encountered in semen from fertile men, although the incidence of abnormalities is low.
BACKGROUND: There is an accumulating body of research showing that smoking causes hearing loss; however, the results of these studies have been inconsistent. METHODS: Original English articles were retrieved by MEDLINE search using key words "smoking" and "hearing" (1966-2003). Of 166 relevant studies, those that investigated the risk for hearing loss in smokers identified by pure-tone average were selected for review. Studies with an occupational noise-exposed population were excluded. Methodological quality was assessed by a standardized checklist, and then a meta-analysis was performed on studies with discrete numbers of hearing loss among smokers and nonsmokers. RESULTS: A total of 15 (10 cross-sectional, 4 cohort, and one case-control) observational studies were identified; the quality scores of the 9 studies with positive associations between smoking and hearing loss were comparable to those of the remaining 6 studies with insignificant associations. Concerning eight analyzable studies, risk ratios (95% confidence intervals) for hearing loss in smokers were 1.33 (1.24, 1.44) for cross-sectional studies, 1.97 (1.44, 2.70) for cohort studies, and 2.89 (2.26, 3.70) for case-control studies, respectively. CONCLUSIONS: The evidence was suggestive of a positive association between smoking and hearing loss. It is possible that smoking cessation may be a useful strategy for maintaining hearing acuity.