International variation in the incidence of hip fractures: cross-national project on osteoporosis for the World Health Organization Program for Research on Aging.

A cross-national study of hip fracture incidence was carried out in five geographic areas--Beijing, China; Budapest, Hungary; Hong Kong; Porto Alegre, Brazil; and Reykjavik, Iceland--during the years 1990-1992. Cases of hip fracture among women and men of age 20 years and older were identified using hospital discharge data in conjunction with medical records, operating room logs, and radiology logs. Estimated incidence rates varied widely, with Beijing reporting the lowest rates (age-adjusted rate per 100,000 population for men 20 years and older = 45.4; women = 39.6) and Reykjavik the highest rates (man = 141.3; women = 274.1). Rates were higher for women than for men in every area except Beijing. In every area except Budapest, review of the operating room or radiology logs identified additional cases that were not reported in the discharge list, increasing the estimated number of hip fractures by 11% to 62%, depending on the area. Review of medical records identified miscoding of hip fractures (ICD 9820) as 'shaft of femur and other femur fractures' (ICD 9821) in the discharge lists of every area except Budapest, increasing the estimated number of hip fractures by 1% to 30%. The final estimates of hip fracture incidence taking into account all investigated sources of undercount and overcount ranged from 15% lower to 89% higher than an estimate based on the discharge diagnoses alone. Although these results indicate substantial limitations in relying on hospital discharge data alone to estimate hip fracture incidence rates, the extent of errors found in the discharge lists is smaller than the large international variation found here and previously reported in incidence rates. The findings support the conclusion that the differences reported among countries mainly reflect genuine variation in the hip fracture incidence rates.

Industrialization, electromagnetic fields, and breast cancer risk.

The disparity between the rates of breast cancer in industrialized and less-industrialized regions has led to many hypotheses, including the theory that exposure to light-at-night and/or electromagnetic fields (EMF) may suppress melatonin and that reduced melatonin may increase the risk of breast cancer. In this comprehensive review we consider strengths and weaknesses of more than 35 residential and occupational epidemiologic studies that investigated the association between EMF and breast cancer. Although most of the epidemiologic data do not provide strong support for an association between EMF and breast cancer, because of the limited statistical power as well as the possibility of misclassification and bias present in much of the existing data, it is not possible to rule out a relationship between EMF and breast cancer. We make several specific recommendations for future studies carefully designed to test the melatonin-breast cancer and EMF-breast cancer hypotheses. Future study designs should have sufficient statistical power to detect small to moderate associations; include comprehensive exposure assessments that estimate residential and occupational exposures, including shift work; focus on a relevant time period; control for known breast cancer risks; and pay careful attention to menopausal and estrogen receptor status.

Smoking and blood pressure patterns in normotensive pregnant women.

This paper examines the relationship between smoking levels and blood pressure patterns of normotensive pregnant women in a prospective cohort of 2193 primiparous and 3176 multiparous, normotensive, Caucasian women selected from the Child Health and Development Studies in Oakland, California, 1959-67. Regression lines were fitted to each woman's blood pressure; mean intercept and slope estimates of the individual regressions were used to create summary profile lines for each smoking dose. Multivariable regression analysis controlled for maternal age, number of visits to the doctor after 20 weeks' gestation, body mass index and maternal education level. Overall, smokers had lower average diastolic blood pressure (smokers vs. nonsmokers adjusted mean: primiparas, 66.1 vs. 67.2 mmHg; and multiparas, 64.0 vs. 64.7 mmHg) but higher systolic blood pressure (smokers vs. nonsmokers adjusted mean: primiparas, 117.0 vs. 116.0; and multiparas, 112.5 vs. 110.0) than nonsmokers among primiparous and multiparous pregnant women after adjusting for potential confounders. However, these differences are small and there was no clear dose-response relationship between smoking level and blood pressure.

Two measures of physical activity as predictors of bone mass in a young cohort.

OBJECTIVE: To compare the association of two measures of physical activity with bone mass in healthy children and young adults, as part of a larger study on bone mineral acquisition in youth. DESIGN: Cross-sectional observation study. SETTING: General community, outpatient study. PARTICIPANTS: Subjects included 103 non-Hispanic white female (n = 54) and male (n = 49) healthy volunteers aged 9 to 25 years. MAIN OUTCOME MEASURES: Self-reported physical activity was measured by a 3-day activity diary of all activities and a questionnaire designed to capture recreational activities throughout the year. Activity was expressed as hours per week of weight-bearing and non-weight-bearing activity. Bone mass at the hip, spine, and whole body was measured by dual x-ray absorptiometry. RESULTS: The activity measures were not well correlated with each other. In males, weight-bearing and non-weight-bearing activity reported in 3-day diaries was positively associated with bone mass at the hip, spine, and whole body (p < 0.05). Among females, only weight-bearing activity measured by the yearly questionnaires was significantly positively associated with bone mass (p < 0.05). In males and females, weight-bearing activity was more highly correlated with bone mineral than was non-weight-bearing activity. In addition, the associations between activity and bone mass varied by skeletal site. CONCLUSIONS: The association between physical activity and bone mass varied both in direction and in significance depending on the physical activity instrument used. Gender differences were observed in the associations between specific activity instruments, type of activity (weight-bearing and non-weight-bearing), and bone mass at different skeletal sites. Variability associated with the two physical activity measures may contribute to discrepant findings in this study and in the literature.

Occupational electric and magnetic field exposure and leukemia. A meta-analysis.

We conducted a meta-analysis to acquire an understanding of the association between leukemia and occupational exposure to electric and magnetic fields. To explore sources of heterogeneity, study characteristics were scored and examined using regression analysis. While most studies present a small elevation in risk, the apparent lack of a clear pattern of exposure to EMF and risk of leukemia substantially detracts from the hypothesis that measured magnetic fields in the work environment are responsible for the observed excess risk of leukemia. Findings were not sensitive to assumptions, influence of individual studies, weighting schemes, and modeling. Some evidence of publication bias is noted.