Objective:Aging caused by a deficiency syndrome can be found in ancient and mod traditional Chinese medicine literature.Qi deficiency syndrome (QDS) is a vital factor in the aging process.This study aimed to establish a full-scale trial to evaluate the prevalence,symptom severity,frequency,and distribution of QDS in different age groups and varying health status to elucidate the role of qi deficiency in the aging process and deterioration of health.Methods:This cross-sectional study was conducted in four hospitals in China,and data from 1220 participants were included.The participants,aged between 20 and 79 years,completed questionnaires that recorded prevalence of QDS and severity or frequency of relevant symptoms,then were interviewed by investigators.We used frequency analysis and chi-squared tests to perform comparative analysis of prevalence in different age and health groups;we used a ranksum tests for quantitative analysis of symptoms severity and frequency scores;we performed a regression analysis of correlation between syndrome occurrence and potential factors using nonconditional binary logistic stepwise regression of numerical variables.P ＜ 0.05 was considered statistically significant.Results:Prevalence,symptom severity and frequency scores of QDS showed a rising trend when physical condition worsened,rather than when age increased.Health status,fatigue,shortness of breath or no desire to talk,spontaneous sweating,swollen tongue with teeth marks on side,and deficient and weak pulse,rather than increasing age were contributing factors to this syndrome.Distribution of QDS in certain health and age stages showed remarkable irregularities.Conclusions:Qi deficiency may be a contributing factor for sub-health (sub-optimal health) and chronic diseases rather than aging.It may play a crucial role in chronic disease pathogenesis of young and middle-aged people,and in sub-health pathogenesis of older adults.Recognition of the wing signs and symptoms of QDS may lead to early intervention and prevention of subhealth,and chronic diseases.