A prospective study (1985-1991) was conducted to evaluate the role of nutrition, physical activity, and other life-style factors for the age at menarche, a known breast cancer risk factor. In 1988-1989, a total of 261 girls, aged 8-15 years, from a nationwide representative nutrition and activity survey (1985-1988) responded additionally to a mailed questionnaire on personal maturation and anthropometric data, physical activity, and information about nutritional habits, measured by a short food-frequency questionnaire. All girls without menarche at the time of questionnaire mailing were observed for 2 years or until the event of menarche. At the end of the follow-up period, 79% of the girls had experienced menarche. The survey and questionnaire data were analyzed for their relation to age at menarche using Cox's proportional hazards method. After excluding participants with largely deviating measurements between survey and questionnaire, the increased energy-adjusted fat intake was associated with accelerated menarche (relative risk = 2.1; 95% confidence interval 1.1-4.0; lowest vs. highest quartile), while increased sports activity was associated with a delay in menarche (relative risk = 0.3; 95% confidence interval 0.1-0.5; lowest vs. highest quartile). Parameters of physical development such as body weight or body fatness were found to be predictors of menarche. The study provides evidence that dietary effects on breast cancer risk might be indirect by influencing hormonal events like the age at menarche.

This endemic occupational disease has become a foodborne and travel-associated zoonosis primarily affecting Turkish immigrants.

BackgroundCarlsen and coworkers (1992) reviewed 61 heterogeneous observational studies on semen quality published between 1938 and 1990. This review indicates that mean sperm density decreased significantly between 1940 and 1990. An extended meta-analysis with 101 studies confirmed a decline in sperm density for the period from 1934 to 1996 (2000). The key message of the meta-analyses is that sperm counts have decreased globally by about 50% over the past decades. This assessment has been questioned.DiscussionA major methodological problem of the meta-analysis is the use of data collected in different countries, at different times, on different populations and with different methods of semen analysis. Furthermore, the results of studies concerning semen analysis are frequently biased e.g. by selection criteria of volunteers. In most studies on human semen characteristics the populations under study are insufficiently defined and the study participants are not a representative population sample. The incidence of testicular cancer has increased in Caucasian men worldwide. The investigation of common risk factors for male reproductive disorders requires well designed epidemiological studies and the collection of individual data.SummaryFormer meta-analyses of sperm count data show a global downward trend. This conclusion should be interpreted with caution. The included studies are of great heterogeneity due to geographical and/or ethnical variation, different study designs and different methodological standards. Population-based prospective studies are needed to investigate secular trends in male reproductive disorders.

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