2.2. Classification of Traditional Chinese Medicine Body Constitution Types

Types of TCM body constitution of the participants were determined based on the Constitution in Chinese Medicine Questionnaire (CCMQ), developed by Wang and his research team [3, 20]. The CCMQ was devised based on the constitutional theory of TCM proposed in the 1970s and was subsequently accepted in 2009 as the national standard of body constitution classification in China. In this study, we used the CCMQ (Hong Kong version), written in traditional Chinese characters, which is based on the CCMQ_60 China Standard version 1.0. Permission for the use of the CCMQ was obtained from the copyright owner Professor Wang Qi through the questionnaire developer of the Hong Kong version in traditional Chinese characters, Professor Wendy Wong at the Chinese University of Hong Kong [21].

The CCMQ consists of 60 Likert response-type items of 1 to 5 representing never, rarely, sometimes, often, and always. Based on a standard scoring algorithm proposed in the original CCMQ [1, 22], an individual can be classified into one or more of the nine types of body constitution. The nine types of body constitution include one type of balanced constitution (gentleness) and eight types of unbalanced constitutions: Qi-deficiency, Yang-deficiency, Yin-deficiency, phlegm-dampness, damp-heat, blood stasis, Qi stagnation, and special diathesis (or inherited special). Briefly, if the score for the balanced constitution ≥60 and all the remaining eight unbalanced constitution score <40, then a balanced constitution was defined. Otherwise, if the score for balanced constitution <60 and Qi-deficiency scores ≥40, then Qi-deficiency constitution was defined, and the determination for the other seven unbalanced constitutions was similarly defined. For individuals who could not be categorized into any body constitution types based on the above algorithm, their body constitutions were assigned as the one with the highest score. A description of typical clinical manifestations of the nine types of body constitution can be found in a review article by Sun et al. [1].

A validation study of the Hong Kong version of the CCMQ showed that the internal reliability Cronbach's α was 0.89 and the intraclass correlation for two-week test-retest reliability ranged from 0.71 to 0.88. Confirmatory factor analysis was able to reproduce the 9-factor structure as the original CCMQ. In addition, no significant flooring or ceiling effect was observed in the CCMQ [21].