Cases control

TABLE 5.8(b) Case-control Studies of Urinary Bladder Cancer annong Workers in the Printing Industry ... 

Gonii.alez, C., Lopez-Abente, G., Errezola, M., Escolar, A., Riboli, E., Izarzugaza, 1., and Nebot, iM. (1989). Occupation and bladder cancer in Spam a multi-centre case-control study. Ini. J. Epidemiol. 18, 569-577. 

Sicmiarycki, )., Dewar, R., Nadon, L.., and Gerin, M. (1994). Occupational risk factors for bladder cancer Results from a case-control study in Montreal, Quebec, Canada. Am. J. Epide-miol. 140, 1061-1080. 

Epidemiological and clinical studies of workers and other long-term case-control studies... 

The two basic types of analytical studies are the cohort and the case-control study. Each has strengths and weaknesses as well as different resource and time requirements. The cohort study involves the study of indi iduals classified by e.xposure characteristics, e.g., a group of welders. The study then follows the development of disease in the welders group as well as in an unexposed comparison population. The measure that assesses the magnitude of... 

In the case-control design, a group with a disease (cases) is compared with a selected group of nondiscased (control) individuals with respect to exposure. The relative risk in control studies can only be estimated as the incidence rate among exposed individuals and cannot be calculated. The estimator used is the odds ratio, which is the ratio of the odds of exposure among the cases to that among the controls. 

Epidemiological and case-control studies suggested that Ca2+ channel blockers cause increased risk for... 

In a case-control study of pesticide factory workers in Brazil exposed to methyl parathion and formulating solvents, the incidence of chromosomal aberrations in lymphocytes was investigated (De Cassia Stocco et al. 1982). Though dichlorodiphenyltrichloroethane (DDT) was coformulated with methyl parathion, blood DDT levels in the methyl parathion-examined workers and "nonexposed" workers were not significantly different. These workers were presumably exposed to methyl parathion via both inhalation and dermal routes however, a dose level was not reported. The exposed workers showed blood cholinesterase depressions between 50 and 75%. However, the baseline blood cholinesterase levels in nonexposed workers were not reported. No increases in the percentage of lymphocytes with chromosome breaks were found in 15 of these workers who were exposed to methyl parathion from 1 week to up to 7 years as compared with controls. The controls consisted of 13 men who had not been occupationally exposed to any chemical and were of comparable age and socioeconomic level. This study is limited because of concomitant exposure to formulating solvents, the recent history of exposure for the workers was not reported, the selection of the control group was not described adequately, and the sample size was limited. 

Case-Control Study—A t5q)e of epidemiological study which examines the relationship between a particular outcome (disease or condition) and a variety of potential causative agents (such as toxic chemicals). In a case-controlled study, a group of people with a specified and well-defined outcome is identified and compared to a similar group of people without outcome. 

In a case-control study of the relation between occupational exposures to various suspected estrogenic chemicals and the occurrence of breast cancer, the breast cancer odds ratio (OR) was not elevated above unity (OR=0.8 95% 01=0.2-3.2) for occupational exposure to endosulfan compared to unexposed controls (Aschengrau et al. 1998) however, the sample sizes were very small (three exposed seven not exposed), and co-exposure to other unreported chemicals also reportedly occurred. Both of these factors may have contributed to the high degree of uncertainty in the OR indicated by the wide confidence interval. 

Strength of recommendation A based on a meta-analysis or at least one randomized controlled trial. Strength of recommendation B based on at least one well-designed study, including case control and comparative studies. Strength of recommendation C based on expert reports or opinion (levels of evidence and strength of recommendation. Oxford (UK) Centre for Evidence-Based Medicine. Available at http //www.cebm.net/levels of evidence.asp (accessed December 8,2008). 

Loss of insurance coverage (in a postmarketing case control study)... 

Cui L, Locatelli L et al (1997) Effect of nucleoside analogs on neurite regeneration and mitochondrial DNA synthesis in PC-12 cells. J Pharmacol Exp Ther 280(3) 1228-1234 Dal Pan GJ, Glass JD et al (1994) Clinicopathologic correlations of HIV-l-associated vacuolar myelopathy an autopsy-based case-control study. Neurology 44(11) 2159-2164 Dalakas MC (2001) Peripheral neuropathy and antiretroviral drugs. J Peripher Nerv Syst 6(l) 14-20 Dalakas MC, Semino-Mora C et al (2001) Mitochondrial alterations with mitochondrial DNA depletion in the nerves of AIDS patients with peripheral neuropathy induced by 2 3 -dideoxycytidine (ddC). Lab Invest 81(11) 1537-1544... 

Lohmoller G, Matuschke A et al (1989) [False-positive test of autonomic neuropathy in HIV infection and AIDS Case control study of heart rate variability in 62 HIV positive patients]. Med Klin (Munich) 84(5) 242-245... 

A retrospective case-control study conducted in humans compared spontaneous abortion rates among women who had been exposed occupationally or nonoccupationally to trichloroethylene and other solvents to rates among women without solvent exposure (Windham et al. 1991). The authors observed approximately three times the risk of spontaneous abortion with exposure to trichloroethylene. This risk increased further when women with less than a half hour of exposure to trichloroethylene each week were excluded from the analysis. However, a consistent dose-response relationship was not observed, and most of the women were exposed to a variety of solvents, not just trichloroethylene. 

Reproductive Toxicity. Increased miscarriages were reported in one study of nurse-anesthetists exposed to trichloroethylene and other solvents (Corbett et al. 1974). A retrospective case-control study has should an approximate 3-fold increase in spontaneous abortion in women exposed to trichloroethylene and other solvents (Windham et al. 1991). Significant effects on sperm parameters were not observed in men occupationally exposed to trichloroethylene (Rasmussen et al. 1988). Adverse reproductive effects were not noted in humans that ingested water contaminated with trichloroethylene and other solvents (Byers et al. 

Hardell L, Eriksson M, Lenner P, et al. 1981. Malignant lymphoma and exposure to chemicals, especially organic solvents, chlorophenols and phenoxy acids A case-control study. Br J Cancer 43 169-176. 

NEGRI L, LAVECCHiA c and FRANCESCHi s (2002) Relations between vegetable, fruit and micronutrient intake. Imphcations for odds ratios in a case-control stndy , Eur J Clin Nutr, 56, 166-70. 

H, YU s z and kurtz r c (2000) GSTTl and GSTMl null genotypes and the risk of gastric cancer a case-control study in a Chinese population . Cancer Epidemiol Biomarkers Prev, 9 73-80. 

Dietary determinants of limg cancer risk results from a case-control smdy in Yimnan Province, China. Int J Cancer. 50 876-80. 

YU G p, HsiEH c c, WANG L Y, YU s z, LI x L and JIN T H (1995) Green tea consiunption and risk of stomach cancer a population-based case-control smdy in Shanghai, China , Cancer Causes Control, 6, 532-8. 

An inverse correlation between thyroid cancer risk and phytoestrogens was recently proposed as a result of a multi-ethnic population-based case control study conducted in the San Francisco Bay Area (Hom-Ross et al., 2002). In this study, dietary habits and phytoestrogen consumption were assessed by a food-frequency questionnaire and by a nutrient database. The outcome of the study was that soy-based foods and alfalfa sprouts were associated with a reduction of thyroid cancer risk, whereas a Western diet did not influence cancer risk. No difference was observed between American and Asian women or between pre- and postmenopausal women. Furthermore, among the few compounds examined, the isoflavones genistein and daidzein and the lignan secoisolariciresinol were the phytoestrogens most frequently associated with risk reduction (Horn-Ross et al., 2002). 

NEWMAN T B, BROWNER s w, CUMMINGS s R, HULLEY s B (1988) Designing a new study 11. Cross-sectional and case-control studies, in Hulley S B and Cummings S R, Designing Clinical Research, Baltimore, Williams Wilkins, 75-86. 

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