Journal of Affective Disorders 169 (2014) 36–39
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Long-term Tai Chi training is related to depressive symptoms among Tai Chi practitioners Yingjie Li a,1, Qian Su b,1, Hui Guo b, Hongmei Wu b, Huanmin Du b, Guang Yang c, Ge Meng d, Changping Li e, Ryoichi Nagatomi f, Kaijun Niu b,n a
Tianjin University of Sport, Tianjin, China Nutritional Epidemiology Institute and School of Public Health, Tianjin Medical University, 22 Qixiangtai Road, Heping District, Tianjin 300070, China c College of Sports Science, Shenyang Normal University, Shenyang, China d Department of Toxicology, School of Public Health, Tianjin Medical University, Tianjin, China e Department of Health Statistics, College of Public Health, Tianjin Medical University, Tianjin, China f Division of Biomedical Engineering for Health & Welfare, Tohoku University Graduate School of Biomedical Engineering, Sendai, Japan b
art ic l e i nf o
a b s t r a c t
Article history: Received 15 July 2014 Accepted 22 July 2014 Available online 31 July 2014
Background: Due to the close association with physical and psychological health and quality of life, mood disorders, especially depressive symptoms, are an important global public-health issue. It is hypothesized that long-term physical training and mood adjustment may have a beneﬁcial effect on the prevention of the onset of depressive symptoms. The aim of this study was to investigate the relationship between long-term Tai Chi training and depressive symptoms among Tai Chi practitioners. Methods: This study analyzed a cross-sectional survey including 529 Japanese Tai Chi practitioners. Tai Chi training information, including total training time and a Tai Chi grade, was assessed using a structured questionnaire, and depressive symptoms were evaluated using the 15-item Geriatric Depression Scale (GDS) for subjects aged Z 65 and the 20-item Self-rating Depressive Scale (SDS) for subjects aged o 65 with cut-off points: GDS Z5 and SDS Z 11. Results: The prevalence of depressive symptoms was 15.9%. After adjustments for potential confounding factors, the odds ratios of having depressive symptoms by increasing levels of Tai Chi training time were 1.00, 0.64 (0.37–1.11), 0.65 (0.37–1.13), 0.34 (0.18–0.65) (P for trend o 0.01). Limitations: This is a cross-sectional study, and not for making a clinical diagnosis of depressive symptoms. Conclusions: This study has demonstrated that long-term Tai Chi training is independently related to a lower prevalence of depressive symptoms. These results suggest that long-term Tai Chi training may have a beneﬁcial effect on the prevention of depressive symptoms. Further studies are needed to conﬁrm these ﬁndings. & 2014 Elsevier B.V. All rights reserved.
Keywords: Tai Chi Depressive symptoms
1. Introduction Depressive mood disorders are some of the most common psychological disorders with characteristics of chronicity, recurrence and relatively high lifetime prevalence in the general population. Due to the close association between physical and psychological health and quality of life (Blazer, 2003), mood disorders are an important global public health issue. Although depressive disorders can be treated with drug therapy and psychological intervention, symptoms can be difﬁcult due to an incomplete understanding of the pathophysiology
Corresponding author. Tel.: þ 86 22 83336613. E-mail addresses: [email protected]
, [email protected]
(K. Niu). 1 Co-ﬁrst author with equal contribution.
http://dx.doi.org/10.1016/j.jad.2014.07.029 0165-0327/& 2014 Elsevier B.V. All rights reserved.
underlying this group of disorders, a lack of medical resources, and poor controllability (Williams et al., 2000). Prevention programs that penetrate into our daily lives could be an effective way to reduce the prevalence of depressive symptoms, but such programs have not yet been established. A scientiﬁcally-based effective method to inhibit the onset and development of depressive symptoms and was based on traditional physical training would likely draw considerable attention from mood disorderrelated ﬁelds. Tai Chi is a traditional Chinese combat skill, crafted in the 17th century (China Sports Editorial Board, 1983). As an internal-style martial art, it is helpful not only for building ﬁtness but is also important for the adjustment of mood (Cheng, 1999; Delza, 1985; Xu and Fan, 1988). Long-term physical training (Singh. et al., 2001) and mood adjustment (Williams et al., 2000) may have a beneﬁcial effect on the prevention of the onset of depressive symptoms.
Y. Li et al. / Journal of Affective Disorders 169 (2014) 36–39
Since practicing Tai Chi is associated with improved physical health and psychological recovery (Chou et al., 2004; Jin, 1992), it was hypothesized that long-term Tai Chi training may be a preventative tool for depressive symptoms. However, few studies have investigated the effect of Tai Chi on the prevention of depressive symptoms, or examined its utility as a prescription exercise therapy for psychological intervention. Therefore, we conducted a cross-sectional analysis to examine the relationship between long-term Tai Chi training and depressive symptoms, with the aim of providing evidence for prescription mental rehabilitation to reduce the prevalence of depressive symptoms through long-term Tai Chi training.
2. Subjects and methods 2.1. Study participants A structured questionnaire was distributed to 733 individuals who practiced Tai Chi (members, Miyagi Prefecture of Japan Wushu Taijiquan Federation) between October and December 2006. Questionnaires were distributed and collected by mail with a total response rate of 78%. Of these, 65 questionnaires were excluded because subjects either had not ﬁlled in the duration of Tai Chi training, or not provided answers to the depression scale questions. The remaining 529 questionnaires were included in the ﬁnal analysis. The study was approved by Tohoku University Ethics Committee and written informed consent was obtained from all participants. 2.2. Assessment of Tai Chi training The following information was collected in the assessment: number of years of training; frequency of training (times per week); and average duration of training sessions (hours) were contained in the assessment. Each subject was positioned as different grade levels using the Japanese Dan grading system. Mainly according to the length of time of Tai Chi training, Dan grade was deﬁned as 5 grades (level 1 to 5) from high to low and 3 Dan (1st Dan to 3rd Dan) from low to high (Japan WuShu TaiJiQuan Federation, 2012).
2.3. Assessment of depressive symptoms Depressive symptoms were evaluated using the Zung 20-item Self-Rating Depression Scale (SDS) (Fukuda and Kobayashi, 1973) for subjects aged o65 and the 15-item Geriatric Depression Scale (GDS) (Niino et al., 1991) for subjects aged Z65. Both scales were examined for reliability and validity. Total possible scores for the SDS and GDS are 80 and 15, respectively; the higher the score, the more severe the symptoms. Scores over 40 (for the SDS) and 5 (for the GDS) indicate depressive symptoms (Barrett et al., 1978). 2.4. Assessment of other variables The information collected included gender, age, height, weight, body mass index (BMI), Occupation (yes, no), education, cohabitation (yes, no), possession of spouse, sleep time and quality, smoking and drinking habits, and history of disease. Physical activity was evaluated using the International Physical Activity Questionnaire (IPAQ), shown to have great reliability and validity. Total activity was calculated by multiplying Metabolic Equivalent of Task (MET) values hours/week (Craig et al., 2003).
2.5. Statistical analysis The length of time of Tai Chi training was used as an independent variable in quartiles, and depressive symptoms were used as dependent variables. Multiple logistic regression analysis was used to evaluate the correlation between Tai Chi training and depressive symptoms. Confounding factors included gender, age, BMI, physical activity, education (undergraduate or above), Dan grade, cohabitation, possession of spouse, smoking and drinking habits, and history of disease, etc (see Table 2 for details). Statistical Analysis System 9.2 edition (SAS Institute Inc., Cary, NC, USA) was used to analyze the association of the length of time of Tai Chi training with other variables; all tests were two-tailed and used logistic regression analysis (for the count data) or analysis of variance (for the measurement data). Due to abnormal distribution, physical activity data were transformed into the corresponding logarithmic values. A linear trend across increasing
Table 1 Characteristics of subjects according to quartiles of the total time of Tai Chi traininga. P for trendb
The quartiles of the total time of Tai Chi training (range, h)
No. of subjects Age4 60 yr (%) Female (%) BMI (m2/kg) Dan gradesZ level 1 (%) Above bachelor (%) cohabitation (yes, %) Possession of spouse (%) Occupation (yes, %) Sleeping time 7–8 h (%) Good quality of sleep (%) Drinking habit Often (%) Ex-smoker (%) Smoking habit Often (%) Ex-smoker (%) No. of diseases Z2 (%) Physical activity (log-transformed METs hours/week) a b c
Level 1 (4–208)
Level 2 (216–476)
Level 3 (480–1280)
Level 4 (1296–12,096)
128 52.3 78.1 22.2 (21.8–22.7)c 2.3 23.4 90.6 77.3 82.8 50.0 84.4 – 53.1 5.5 – 6.3 20.3 33.6 3.03 (2.89–3.17)
135 51.9 85.2 22.4 (22–22.8) 11.9 19.3 87.4 83.7 83.7 54.8 87.4 – 48.2 5.2 – 8.2 11.9 34.8 3.19 (3.05–3.33)
133 60.2 85.7 22.2 (21.8–22.7) 51.1 18.1 84.2 74.4 82.7 64.7 93.2 – 42.1 6.8 – 7.5 12.0 37.6 3.24 (3.10–3.38)
133 66.9 86.5 22.6 (22.1–23.0) 85.0 12.0 85.0 80.5 82.0 56.4 86.5 – 49.6 6.8 – 2.3 11.3 36.8 3.61 (3.47–3.75)
BMI, body mass index; MET, metabolic equivalent. Analysis of variance or logistic regression analysis. Variables are presented as mean (95% conﬁdence interval) (all such values).
– o0.01 0.22 1.00 o0.0001 0.02 0.29 0.85 0.76 0.57 0.99 0.95 0.60 0.055 0.19 0.64 0.04
Y. Li et al. / Journal of Affective Disorders 169 (2014) 36–39
Table 2 Adjusted relationship between time of Tai Chi training and depressive symptomsa. Odds ratio (95% conﬁdence interval)
No. of subjects No. of depressive symptoms Crude Age- and sex-adjusted Multiple adjustedc
P for trendb
The quartiles of the total time of Tai Chi training (range, h) Level 1 (4–208)
Level 2 (216–476)
Level 3 (480–1280)
Level 4 (1296–12,096)
128 43 1.00 1.00 1.00
135 34 0.67 (0.39–1.13) 0.66 (0.38–1.13) 0.64 (0.37–1.11)
133 32 0.63 (0.36–1.07) 0.66 (0.38–1.14) 0.65 (0.37–1.13)
133 18 0.31 (0.16–0.57) 0.34 (0.18–0.63) 0.34 (0.18–0.65)
– o 0.001 o 0.01 o 0.01
Deﬁnition of depressive symptoms: Z 65 yr, Geriatric Depression Scale Z 5; o 65 yr, Self-rating Depression Scale Z 40. Multiple logistic regression analysis. Adjusted for gender, age, body mass index, Dan grades of Tai Chi, occupation, education, cohabitation, possession of spouse, sleeping time and sleeping quality, smoking and drinking habits, history of diseases, and physical activity. b c
quartiles was tested by using the median value of each quartile as an ordinal variable. The interactions between Tai Chi training and all confounders for having depressive symptoms were tested through the addition of the cross-product terms to the regression model. A difference was considered signiﬁcant when P values o0.05.
3. Results 3.1. Characteristics of subjects The 529 subjects analyzed in the study had a minimum total time of Tai Chi training of 4 h and a maximum of 12,096 h and the prevalence of depressive symptoms was 15.9% in this population. As shown in Table 1, the proportion of elderly was signiﬁcantly increased for higher training times. According to the criteria of Japanese Tai Chi Dan grading system, increasing Dan grades above level 1 were associated with increasing percentages of elderly subjects, whose physical activity also improved signiﬁcantly. But time of Tai Chi training was in inversely proportional to higher education, indicating that higher education may not be signiﬁcantly correlated with a stronger concept of sport. Differences among other variables were not statistically signiﬁcant. 3.2. Association between length of time of Tai Chi training and depressive symptoms Table 2 shows the adjusted relationship between the quartile of the length of time of Tai Chi training and depressive symptoms: odds ratios (ORs) for depressive symptoms decreased with increasing time of training (P for trend o 0.001). Age- and sexadjusted ORs (95% CI) for depressive symptoms across the quartile of length of time of Tai Chi training were 1.00, 0.66 (0.38–1.13), 0.66 (0.38–1.14), and 0.34 (0.18–0.63) (P for trend o0.01). These results were unchanged when adjusted for multiple confounding factors. Similar relationships were also observed when males and females were analyzed separately (P for interaction ¼0.52). Tests for interactions between categories of length time of Tai Chi training and these potential confounders in the ﬁnal models were found to be not signiﬁcant (P for interaction 40.13).
Tai Chi training may play a positive role in the prevention of depressive symptoms in the general population. Previous studies have demonstrated that Tai Chi training enhances muscle strength (Guo et al., 2007), reduces number of falls (Leung et al., 2011), and boosts immunity (Blake and Hawley, 2012). Based on these ﬁndings, we hypothesized that Tai Chi might have an equivalent effect on the prevention of depressive symptoms; indeed, we ﬁnd this to be the case. But how does Tai Chi practice positively impact depressive mood outcomes? We believe the answer is two-fold: on one hand is the effect of exercise itself and on the other is psychological adjustment. It has been shown that regular exercise can improve depressive symptoms (Blake et al., 2009); Tai Chi, as an exercise program, is well suited to people with different physical abilities, especially the elderly (who have a greater incidence of depressive symptoms). Tai Chi training is beneﬁcial to one's physiological state; it helps regulate breathing, raise ones level of consciousness, and achieve serenity, which has beneﬁcial effects on psychological stability by abating mental stress (the leading cause of depressive symptoms (Pittenger and Duman, 2008)). Other studies have suggested that short-term Tai Chi training could improve depressive symptoms (Cho, 2008; Lavretsky et al., 2011; Yeung et al., 2012), but patients in those studies had no experience with Tai Chi training prior to the study. In contrast, in our study, all participants had experienced Tai Chi training. Our study demonstrates that Tai Chi training can promote long-term psychological stability. In this study, a number of potential confounding factors that could inﬂuence the results were analyzed, including age, gender, BMI, Dan grade, education, cohabitation, possession of spouse, occupation, sleep time and quality, smoking and drinking habits, history of disease and physical activity. Even after adjusting for these potential confounders, the signiﬁcant relationship between length of time of Tai Chi training and depressive symptoms remained, indicating that it is independently associated with depressive symptoms. One limitation of this study is while the GDS and SDS do assess depressive symptoms, they are not a substitute for clinical diagnoses; therefore, further study is necessary to explore whether Tai Chi training correlates with clinical diagnosis of depressive mood disorders. In addition, since cross-sectional studies cannot determine causal relationships, a long-term cohort follow-up study would verify the hypothesis tested here. Finally, although several potential confounders were considered, effects of other factors on depressive mood symptoms could not be excluded.
4. Discussion The study was the ﬁrst to comprehensively evaluate the relationship between Tai Chi training and depressive symptoms, and our results revealed that the proportion of adults with depressive symptoms declined signiﬁcantly with increased length of Tai Chi training time. Our results demonstrate that long-term
5. Conclusion With increased time investment, the prevalence of depressive symptoms signiﬁcantly declined in Tai Chi practitioners, a trend that is maintained after adjusting for multiple confounding factors.
Y. Li et al. / Journal of Affective Disorders 169 (2014) 36–39
We therefore suggest that not only practicing regular exercise but also incorporating regular and frequent Tai Chi training into ones daily routine is important for the prevention and improvement of depressive symptoms, particularly in the elderly.
Role of funding source Nothing declared.
Conﬂict of interest All the authors have no conﬂicts of interest exists to disclose.
Acknowledgments This study was supported by a Grant-in-Aid for ″Knowledge Cluster Initiative″ from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and Grant-in-Aid for Young Scientists (11CTY023) from National Social Science Fund of China.
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