PURPOSE Rheumatoid arthritis (RA) is a chronic multi-systemic disease that causes damage to the bone and connective tissues. This study was conducted in order to accurately measure the correlation between RA and periodontitis, and to obtain an unbiased estimate of the effect of RA on periodontal indices. METHODS In this historical cohort study, which was conducted from February to May 2011 in...

OBJECTIVE To understand the underlying mechanism of the "curse of the rainbow jersey," the lack of wins that purportedly affects the current cycling world champion. DESIGN Historical cohort study. SETTING On the road. PARTICIPANTS Professional cyclists who won the World Championship Road Race or the Tour of Lombardy, 1965-2013. MAIN OUTCOME MEASURES Number of professional wins per seaso...

BACKGROUND Tubal ligation (TL) is recommended for women who have completed their family planning. The existence of the menstrual disorders following this procedure has been the subject of debate for decades. This study was conducted to identify the relationship between tubal ligation and menstrual disorders. MATERIALS AND METHODS A historical cohort study was carried out on 140 women undergoi...

BACKGROUND Occupation is a significant factor affecting life, health and well-being. Long-term military service is a unique career path that may have an influence on life expectancy, even after excluding obvious risks such as battlefield mortality. However, it remains unclear what the effects of a military career are on the life trajectory of personnel after retiring from service. This study co...

There is increased emphasis on using experimental and quasi-experimental methods to evaluate educational programs; however, educational evaluators and school leaders are often faced with challenges when implementing such designs in educational settings. Use of a historical cohort control group design provides a viable option for conducting quasi-experiments in school-based outcome evaluation. A...

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&nbsp;Introduction: Controversies exist in publications about the association between shift work and hypertension. This study aimed to explore the relationship between shift work and the level of systolic and diastolic blood pressure as well as serum cholesterol among nurses in Kerman province, Southeast, Iran. &nbsp; Materials and Methods : In this historical cohort study 100 hospital nurse...