Study Designs: Case-control/Retrospective Studies (Page 10 of 15) Antecedent-consequent relationships usually not known - which came first the risk factor or the disease. Cannot calculate the relative risk. Cannot calculate attributable risk. The following examples of case control studies can be viewed in full text through OVID. McElroy JA, Shafer MM, Trentham-Dietz A, Hampton JM, Newcomb PA (2006). Cadmium exposure and breast cancer risk. J Natl Cancer Inst. 98(12), 869-73. Cadmium, a highly persistent heavy metal, has been categorized as a probable human carcinogen by the U.S. Environmental Protection Agency. Primary exposure sources include food and tobacco smoke. We carried out a population-based case-control study of 246 women, aged 20-69 years, with breast cancer and 254 age-matched control subjects. We measured cadmium levels in urine samples by inductively coupled plasma mass spectrometry and conducted interviews by telephone to obtain information on known breast cancer risk factors. Odds ratios (ORs) and 95% confidence intervals (CIs) for breast cancer by creatinine-adjusted cadmium levels were calculated by multivariable analysis. Statistical tests were two-sided. Women in the highest quartile of creatinine-adjusted cadmium level (> or = 0.58 microg/g) had twice the breast cancer risk of those in the lowest quartile (<0.26 microg/g; OR = 2.29, 95% CI = 1.3 to 4.2) after adjustment for established risk factors, and there was a statistically significant increase in risk with increasing cadmium level (P(trend) = .01). Based on this study, the absolute risk difference is 45 (95% CI = 0 to 77) per 100,000 given an overall breast cancer rate of 124 per 100,000. Whether increased cadmium is a causal factor for breast cancer or reflects the effects of treatment or disease remains to be determined. Rachel J. Witsaman, BA, R. Dawn Comstock, PhD, Gary A. Smith, MD, DrPH (2006) Pediatric Fireworks-Related Injuries in the United States: 1990-2003. PEDIATRICS, 118, 296-303. Our goal was to describe the epidemiology of pediatric fireworks-related injuries among children aged 19 years and younger by using a nationally representative sample. We performed a retrospective analysis of data from the US Consumer Product Safety Commission's National Electronic Injury Surveillance System from 1990-2003. We found that an estimated 85 800 pediatric fireworks-related injuries were treated in US emergency departments during the 14-year study period. Injured children had a mean age of 10.8 years, and 77.9% were male. Fireworks users accounted for 49.5% of the injuries, whereas 22.2% of the injuries were to bystanders; however, user status could not be determined in 28.3% of cases. The overall fireworks related injury rate decreased significantly during the study period, but subgroup analysis did not indicate consistent declines among all ages and types of fireworks. Injuries were most commonly caused by firecrackers (29.6%), sparklers/novelty devices (20.5%), and aerial devices (17.6%). The most commonly injured body sites were the eyeball (20.8%), face (20.0%), and hands (19.8%), and the most common injury type was burns (60.3%). Approximately 91.6% of all children with fireworks-related injuries were treated and released from hospital emergency departments, 5.3% were admitted, and 2.3% were transferred to another institution. Bystanders accounted for 13.3% of admitted cases and 20.6% of transferred cases. Thus, consumer fireworks cause serious preventable injuries among pediatric fireworks users and bystanders in the United States. Parents should be advised to take their children to safer public fireworks displays rather than allowing consumer fireworks to be used by or near their children. A national restriction of consumer fireworks, in accordance with the policy recommendations of the American Academy of Pediatrics, should be implemented to reduce the burden of fireworks-related injuries among children.