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The purpose of this study is to analyze the studies, which include Item Response Theory among the keywords, available in the Web of Science database between 1980-2018 through bibliometric analysis method. A total of 1,367 academic works has been analyzed. The authors, journals and countries having the highest number of studies in the field and their interrelations on the network in terms of collaboration have been determined through common citation analysis performed using Citespace II software. In addition, a word analysis was also conducted to determine most frequently used concepts in the field. As a result of the study it was found that the authors that have made the biggest contribution to the field are De Ayala, Embretson, Reckase, Reise and Chalmers; in addition, the countries making the biggest contribution are respectively US, Netherland, Canada, Spain and China. The number of citations that US got, which is the country that received the highest number of citations with 687 citations, is 7 times higher than Netherland, which is the second most cited country. Moreover, it was found that the journals that were mostly cited are respectively "Psychometrika," "Appl Psych Measurement," "Item Response Theory," "J Edu Measurement" and "Educ Psychol Measurement." As a result of the word analysis based on most repeated words, which was performed for the purpose of determining most popular subjects on the field, it was found that most frequently used words are item response theory, classical test theory, model, validation, reliability, validity and Rasch model.

Background: The Seven Countries Study in the 1960s showed very low mortality from coronary heart disease (CHD) in Japan, which was attributed to very low levels of total cholesterol. Studies of migrant Japanese to the USA in the 1970s documented increase in CHD rates, thus CHD mortality in Japan was expected to increase as their lifestyle became Westernized, yet CHD mortality has continued to decline since 1970. This study describes trends in CHD mortality and its risk factors since 1980 in Japan, contrasting those in other selected developed countries.Methods: We selected Australia, Canada, France, Japan, Spain, Sweden, the UK and the USA. CHD mortality between 1980 and 2007 was obtained from WHO Statistical Information System. National data on traditional risk factors during the same period were obtained from literature and national surveys.Results: Age-adjusted CHD mortality continuously declined between 1980 and 2007 in all these countries. The decline was accompanied by a constant fall in total cholesterol except Japan where total cholesterol continuously rose. In the birth cohort of individuals currently aged 50-69 years, levels of total cholesterol have been higher in Japan than in the USA, yet CHD mortality in Japan remained the lowest: >67% lower in men and > 75% lower in women compared with the USA. The direction and magnitude of changes in other risk factors were generally similar between Japan and the other countries.Conclusions: Decline in CHD mortality despite a continuous rise in total cholesterol is unique. The observation may suggest some protective factors unique to Japanese. [ABSTRACT FROM AUTHOR]