Journal of Physical Activity and Health, 2014, 11, 1430 -1437 http://dx.doi.org/10.1123/jpah.2012-0366 © 2014 Human Kinetics, Inc.
Official Journal of ISPAH www.JPAH-Journal.com ORIGINAL RESEARCH
Gender- and Puberty-Dependent Association Between Physical Activity and Depressive Symptoms: National Survey Among Chinese Adolescents Ying Sun, Jing An, Xi Wang, Ping Zu, and Fang-Biao Tao Background: The study aims to understand the possible gender difference in the associations between physical activity and depressive symptoms during pubertal transition. Methods: Participants were 30,399 children and adolescents of Han ethnicity from urban and rural areas in 8 cities in China. Physical activity (PA) and depressive symptom was assessed by adapted Youth Risk Behavior Survey and Children Depression Inventory (CDI), respectively. Pubertal development was assessed by trained physicians. Results: In China, over 30% boys and 40% girls reported having no vigorous PA (VPA) or moderate PA (MPA) in the past week. In girls, participating in VPA 1 to 2 days/week showed protective effect for depressive symptoms; whereas in boys, participating in MPA 1 to 2 days/week showed protective effect for depressive symptoms at and after genital stage III (G3). Conclusions: Moderate frequency (1 to 2 days/week) in PA undertaken might be encouraged to prevent depressive symptoms among adolescents. Keywords: depression Depression is a common mental health problem in adolescents worldwide, with an estimated 1-year prevalence of 4% to 5% in mid to late adolescence.1–3 Levels of subjective negative affect4 and depression5 both increase during adolescence. Each additional depressive symptom at ages 8 to 10 is associated with a 50% to 80% increase in risk for developing a depressive disorder by age 11 to 13,6 and subthreshold depression in adolescence confers an estimated risk of 67% for a diagnosis of depression by the time individuals are in their early 30s.7 With the popularity of television and computer, Chinese adolescents spend more time on watching TV and computer usage, and less time in PA than ever before.8 According to 2010 China National Physical Fitness and Health Surveillance which includes 166,812 students aged 9 to 18, the prevalence of having been physically active for a total of 60 minutes per day in Chinese students is still low.9 There is a growing literature from population-based studies and randomized controlled trials suggesting that, in addition to the positive role of physical activity (PA) in relation to the prevention of specific diseases and other physical health conditions, regular PA might have an array of mental health benefits.10 Low levels of physical activity (PA) have been shown to be associated with depression in adults.11,12 Several studies that focused on adolescents yielded mixed and inconsistent results. Some support an association between less frequent PA and higher levels of depression among adolescents,13–16 and others could not find the association.17,18 Why are there so many mixed results regarding associations between PA and depression in children and adolescents? Part of the discrepancies might be attributed to methodological variations, such The authors are with the Dept of Maternal, Child, and Adolescent Health, School of Public Health, Anhui Medical University, Hefei, Anhui Province, China. Sun ([email protected]) is corresponding author. 1430
as small sample sizes, narrow age range, and absence of pubertal stage. These factors may be important confounders of the association between PA and adolescent depressive symptoms. In the current study, PA and depressive symptoms were both assessed in a large representative population of Chinese children and adolescents, aiming to investigate if there are gender differences in the association between PA and depressive symptoms at different pubertal stages.
Methods Study Design This research is framed within the larger project entitled ‘China Puberty Research Collaboration.’ The multicentered collaboration was established in September 2010 as a consortium in a partnership among 6 medical universities (Anhui, Shanghai, Wuhan, Zhengzhou, Chongqing Taiyuan, and Kunming) and 2 School Student Health-Care Centers (Shenyang and Guangzhou). The 8-site national collaboration seeks to estimate pubertal growth and development among urban and rural Han Chinese girls and boys, and possible health problems during pubertal transition. Han Chinese constituted about 92% of the population of China.
Participants The lowest study sample in each collaborating centers were required as at least 50 boys and 50 girls of Han ethnicity in each grade (from grade 1 to grade 12) in rural and urban area of each research sites. Each site recruited more than this lowest limit. More detailed information on sample size of 8 research centers could be found elsewhere.19 All the healthy students of Han ethnicity from grade 1 to grade 12 in selected schools were invited to participate in our study. And only those with their parental and their own personal consent took part in physical examination including height, weight, sexual
Physical Activity and Depression in China 1431
maturation assessment (pubertal Tanner stage). Students older than the fourth grade participated in questionnaire part which includes vigorous and moderate physical activity frequency (during the past 7 days), depressive symptoms, and living area.
Measures Height and Weight. Height was measured using a Harpenden
Downloaded by Purdue Univ on 09/19/16, Volume 11, Article Number 7
stadiometer to the nearest 0.1 cm. Weight was measured without shoes on a digital weight scale with a precision of 0.1 kg. Body mass index (BMI) was calculated as weight (in kilograms) divided by height (in meters) squared. The China Body Mass Index Curve for Girls and Boys Aged 0 to 18 Years were used to convert BMI values into age-specific BMI percentile levels.20
Sexual Maturity. Sexual maturity of each child was assessed by physicians. These physicians received special standardized training from an experienced pediatric endocrinologist in each research site. Written descriptions and photographs describing the stages of the sexual maturity indicators used during training were available for reference in the examination centers. Tanner staging was done by palpation of breast tissue in addition to visual inspection in girls and visual inspection of genital in boys. Sexual maturity stages based on the recommendations of Tanner were assigned to each maturity indicators. Each maturity indicator has 5 stages that can be assigned from stage 1, representing immaturity, to stage 5, and indicating full maturity. The notation used in this report for each maturity indicator contains the initial letters as follows: breast development (B), genital development (G). Physical Activity. PA was assessed based on Youth Risk Behavior Survey (YRBS).21 Vigorous physical activity (VPA) is assessed by the question: “On how many of the last 7 days did you exercise or participate in sports activities for at least 20 min that made you sweat and breathe hard, such as basketball, jogging, fast dancing, swimming laps, tennis, fast bicycling, or similar aerobic activities?” Moderate physical activity (MPA) is assessed through the question: “On how many of the past 7 days did you participate in physical activity for at least 30 min that did not make you sweat or breathe hard, such as fast walking, slow bicycling, skating, pushing a lawn mower, or mopping floors?” They include both school and nonschool activities. Response categories ranged from 0 to 7 days. VPA and MPA were analyzed into 4 categories: 0 days/week, 1 to 2 days/week, 3 to 4 days/week and > 4 days/week. Depressive Symptoms. Children’s Depression Inventory (CDI)
was used as the instrument to screen depression in children and adolescents.22 CDI is a validated questionnaire originally developed by Kovacs and has been widely used to measure depression for children and adolescents aged 8 to 18 years in epidemiological studies.23–27 It contains 27 items with a self-rating scale ranging from 0 to 2 (eg, what do you think of yourself? 0 = I like myself; 1 = I do not like myself; 2 = I hate myself) that yield total scores from 0 (no indication of depression) to 54 (high depressive tendencies). The Chinese version of CDI has also been validated, with satisfied internal consistency (Cronbach’s α = 0.85 to 0.89) and test-retest reliability (r = .75 to 0.85) with cut-off point value of 20.28,29 In this study, the CDI Cronbach’s α was 0.85 suggesting an acceptable validity. The term of “depression” based on CDI refers to an epidemiological idea not a clinical diagnosis in this study. That is to say, it definitely means that all adolescents with CDI value of 20 or above were at elevated risk of being depressive, which should not be interpreted as a clinical diagnosis.
Statistical Analysis Preliminary analyses were carried out to detect relationships between the depressive symptoms and associated variable (gender, pubertal stage, PA). Kendall correlation analysis was performed for continuous CDI scores and associated variable (pubertal stage, PA), while intergroup differences were analyzed using analysis of, Student’s t test and Chi square test. Analyses of variance (ANOVAs) were conducted using the general linear model (Proc GLM) in SPSS statistical package. The primary dependent measures in this study were depressive symptom. Collinearity between pubertal stage and age were analyzed through linear regression. According to variance inflation factor (VIF) and tolerance in the equation, puberty and age exhibited strong collinearity. Model parameters consisted of the main effects of VPA, MPA, pubertal stage (breast for girls, genital for boys), BMI category, and VPA× pubertal stage, MPA × pubertal stage, VPA× BMI category, MPA × BMI category interactions as predictors of depressive symptom. Multilevel Binary Logistic regression was used to examine the relationship between VPA, MPA and depressive symptoms. Odds ratios (OR) and their 95% confidence intervals (95% CI) are reported.
Results Demographic Characteristics of the Participants In total, 30,399 children, including 15,388 (50.6%) girls and 15,011 (49.4%) boys, participated in the physical examination. Because children under grade 4 did not participate in the questionnaire survey, data on depressive symptoms were available in 12 158 girls and 9 447 boys. The age ranges from 8.0 to 18.9 years old. Mean age and age range for breast Tanner stage I to Tanner stage V were 8.45 ± 1.56 y (6.0–13.9 y), 10.94 ± 1.68 y (7.4–15.9 y), 13.44 ± 2.14 y (9.3–18.1 y), 15.43 ± 1.89 y (11.0–18.9 y) and 16.32 ± 1.71 y (12.0–18.9 y), respectively. Mean age and age range for genital Tanner stage I to Tanner stage V were 9.26 ± 1.88 y (6.0–14.5 y), 12.32 ± 1.79 y (7.9–16.6 y), 14.37 ± 1.88 y (9.5–18.5 y), 16.32 ± 1.44 y (13.3–18.9 y) and 17.01 ± 1.11 y (14.70–18.9 y), respectively. In boys, about 49.6% and 50.4% are from urban and rural areas, respectively. In girls, about 48.8% and 51.2% are from urban and rural areas, respectively. There is no significant difference in urbanrural area distribution between boys and girls (χ2 = 2.31, P = .129).
VPA and MPA As shown in Table 1, almost one-third of boys had no VPA or MPA during the past week. Compared with boys, no VPA and no MPA participation in girls are even higher (42.8% for VPA; 40.6% for MPA) (χ2 = 278.79, P < .001 for VPA; χ2 = 236.12, P < .001 for MPA). As shown in Figure 1 and Table 1, report rates of VPA or MPA decreased significantly with increase of age and breast Tanner stage among girls. However, in boys, there were no significant decreasing trends of VPA or MPA with age or genital Tanner stage. Figure 1 illustrated change of VPA and MPA report rates with pubertal stage in boys and girls, respectively. It showed that physical activity decreased with pubertal stages except for MPA in boys.
Depressive Symptoms and Its Relation With PA and Pubertal Status The median value of CDI score was 12.27 ± 6.73, with boys scored slightly higher (12.38 ± 6.81) than that among girls (12.18 ± 7.70)
1432
BMI category
Breast /genital Tanner stage
MPA (days/wk)
Total VPA (days/wk)
Factors
1953 (16.7)
V 1868 (15.4)
2738 (23.3)
IV
Overweight
3347 (28.5)
III
10,290 (84.6)
2106 (18.0)
Normal
1586 (13.5)
517 (4.3)
>4
II
1198 (9.9)
3–4
I
5507 (45.3)
514 (4.2)
>4 4936 (40.6)
1203 (9.9)
3–4
1–2
5232 (43.1)
1–2
0
5206 (42.8)
0
12 158
Total n (%)
284 (15.2)
1605 (15.6)
378 (19.4)
486 (17.8)
522 (15.6)
245 (11.6)
194 (12.2)
67 (13.9)
177 (15.5)
679 (12.9)
889(18.6)
78(16.2)
166 (14.5)
590 (11.8)
978(19.4)
1825(15.6)
Depressive n (%)
Girls
0.15
69.49
64.08
110.23
χ2
0.704
Official Journal of ISPAH www.JPAH-Journal.com ORIGINAL RESEARCH
Gender- and Puberty-Dependent Association Between Physical Activity and Depressive Symptoms: National Survey Among Chinese Adolescents Ying Sun, Jing An, Xi Wang, Ping Zu, and Fang-Biao Tao Background: The study aims to understand the possible gender difference in the associations between physical activity and depressive symptoms during pubertal transition. Methods: Participants were 30,399 children and adolescents of Han ethnicity from urban and rural areas in 8 cities in China. Physical activity (PA) and depressive symptom was assessed by adapted Youth Risk Behavior Survey and Children Depression Inventory (CDI), respectively. Pubertal development was assessed by trained physicians. Results: In China, over 30% boys and 40% girls reported having no vigorous PA (VPA) or moderate PA (MPA) in the past week. In girls, participating in VPA 1 to 2 days/week showed protective effect for depressive symptoms; whereas in boys, participating in MPA 1 to 2 days/week showed protective effect for depressive symptoms at and after genital stage III (G3). Conclusions: Moderate frequency (1 to 2 days/week) in PA undertaken might be encouraged to prevent depressive symptoms among adolescents. Keywords: depression Depression is a common mental health problem in adolescents worldwide, with an estimated 1-year prevalence of 4% to 5% in mid to late adolescence.1–3 Levels of subjective negative affect4 and depression5 both increase during adolescence. Each additional depressive symptom at ages 8 to 10 is associated with a 50% to 80% increase in risk for developing a depressive disorder by age 11 to 13,6 and subthreshold depression in adolescence confers an estimated risk of 67% for a diagnosis of depression by the time individuals are in their early 30s.7 With the popularity of television and computer, Chinese adolescents spend more time on watching TV and computer usage, and less time in PA than ever before.8 According to 2010 China National Physical Fitness and Health Surveillance which includes 166,812 students aged 9 to 18, the prevalence of having been physically active for a total of 60 minutes per day in Chinese students is still low.9 There is a growing literature from population-based studies and randomized controlled trials suggesting that, in addition to the positive role of physical activity (PA) in relation to the prevention of specific diseases and other physical health conditions, regular PA might have an array of mental health benefits.10 Low levels of physical activity (PA) have been shown to be associated with depression in adults.11,12 Several studies that focused on adolescents yielded mixed and inconsistent results. Some support an association between less frequent PA and higher levels of depression among adolescents,13–16 and others could not find the association.17,18 Why are there so many mixed results regarding associations between PA and depression in children and adolescents? Part of the discrepancies might be attributed to methodological variations, such The authors are with the Dept of Maternal, Child, and Adolescent Health, School of Public Health, Anhui Medical University, Hefei, Anhui Province, China. Sun ([email protected]) is corresponding author. 1430
as small sample sizes, narrow age range, and absence of pubertal stage. These factors may be important confounders of the association between PA and adolescent depressive symptoms. In the current study, PA and depressive symptoms were both assessed in a large representative population of Chinese children and adolescents, aiming to investigate if there are gender differences in the association between PA and depressive symptoms at different pubertal stages.
Methods Study Design This research is framed within the larger project entitled ‘China Puberty Research Collaboration.’ The multicentered collaboration was established in September 2010 as a consortium in a partnership among 6 medical universities (Anhui, Shanghai, Wuhan, Zhengzhou, Chongqing Taiyuan, and Kunming) and 2 School Student Health-Care Centers (Shenyang and Guangzhou). The 8-site national collaboration seeks to estimate pubertal growth and development among urban and rural Han Chinese girls and boys, and possible health problems during pubertal transition. Han Chinese constituted about 92% of the population of China.
Participants The lowest study sample in each collaborating centers were required as at least 50 boys and 50 girls of Han ethnicity in each grade (from grade 1 to grade 12) in rural and urban area of each research sites. Each site recruited more than this lowest limit. More detailed information on sample size of 8 research centers could be found elsewhere.19 All the healthy students of Han ethnicity from grade 1 to grade 12 in selected schools were invited to participate in our study. And only those with their parental and their own personal consent took part in physical examination including height, weight, sexual
Physical Activity and Depression in China 1431
maturation assessment (pubertal Tanner stage). Students older than the fourth grade participated in questionnaire part which includes vigorous and moderate physical activity frequency (during the past 7 days), depressive symptoms, and living area.
Measures Height and Weight. Height was measured using a Harpenden
Downloaded by Purdue Univ on 09/19/16, Volume 11, Article Number 7
stadiometer to the nearest 0.1 cm. Weight was measured without shoes on a digital weight scale with a precision of 0.1 kg. Body mass index (BMI) was calculated as weight (in kilograms) divided by height (in meters) squared. The China Body Mass Index Curve for Girls and Boys Aged 0 to 18 Years were used to convert BMI values into age-specific BMI percentile levels.20
Sexual Maturity. Sexual maturity of each child was assessed by physicians. These physicians received special standardized training from an experienced pediatric endocrinologist in each research site. Written descriptions and photographs describing the stages of the sexual maturity indicators used during training were available for reference in the examination centers. Tanner staging was done by palpation of breast tissue in addition to visual inspection in girls and visual inspection of genital in boys. Sexual maturity stages based on the recommendations of Tanner were assigned to each maturity indicators. Each maturity indicator has 5 stages that can be assigned from stage 1, representing immaturity, to stage 5, and indicating full maturity. The notation used in this report for each maturity indicator contains the initial letters as follows: breast development (B), genital development (G). Physical Activity. PA was assessed based on Youth Risk Behavior Survey (YRBS).21 Vigorous physical activity (VPA) is assessed by the question: “On how many of the last 7 days did you exercise or participate in sports activities for at least 20 min that made you sweat and breathe hard, such as basketball, jogging, fast dancing, swimming laps, tennis, fast bicycling, or similar aerobic activities?” Moderate physical activity (MPA) is assessed through the question: “On how many of the past 7 days did you participate in physical activity for at least 30 min that did not make you sweat or breathe hard, such as fast walking, slow bicycling, skating, pushing a lawn mower, or mopping floors?” They include both school and nonschool activities. Response categories ranged from 0 to 7 days. VPA and MPA were analyzed into 4 categories: 0 days/week, 1 to 2 days/week, 3 to 4 days/week and > 4 days/week. Depressive Symptoms. Children’s Depression Inventory (CDI)
was used as the instrument to screen depression in children and adolescents.22 CDI is a validated questionnaire originally developed by Kovacs and has been widely used to measure depression for children and adolescents aged 8 to 18 years in epidemiological studies.23–27 It contains 27 items with a self-rating scale ranging from 0 to 2 (eg, what do you think of yourself? 0 = I like myself; 1 = I do not like myself; 2 = I hate myself) that yield total scores from 0 (no indication of depression) to 54 (high depressive tendencies). The Chinese version of CDI has also been validated, with satisfied internal consistency (Cronbach’s α = 0.85 to 0.89) and test-retest reliability (r = .75 to 0.85) with cut-off point value of 20.28,29 In this study, the CDI Cronbach’s α was 0.85 suggesting an acceptable validity. The term of “depression” based on CDI refers to an epidemiological idea not a clinical diagnosis in this study. That is to say, it definitely means that all adolescents with CDI value of 20 or above were at elevated risk of being depressive, which should not be interpreted as a clinical diagnosis.
Statistical Analysis Preliminary analyses were carried out to detect relationships between the depressive symptoms and associated variable (gender, pubertal stage, PA). Kendall correlation analysis was performed for continuous CDI scores and associated variable (pubertal stage, PA), while intergroup differences were analyzed using analysis of, Student’s t test and Chi square test. Analyses of variance (ANOVAs) were conducted using the general linear model (Proc GLM) in SPSS statistical package. The primary dependent measures in this study were depressive symptom. Collinearity between pubertal stage and age were analyzed through linear regression. According to variance inflation factor (VIF) and tolerance in the equation, puberty and age exhibited strong collinearity. Model parameters consisted of the main effects of VPA, MPA, pubertal stage (breast for girls, genital for boys), BMI category, and VPA× pubertal stage, MPA × pubertal stage, VPA× BMI category, MPA × BMI category interactions as predictors of depressive symptom. Multilevel Binary Logistic regression was used to examine the relationship between VPA, MPA and depressive symptoms. Odds ratios (OR) and their 95% confidence intervals (95% CI) are reported.
Results Demographic Characteristics of the Participants In total, 30,399 children, including 15,388 (50.6%) girls and 15,011 (49.4%) boys, participated in the physical examination. Because children under grade 4 did not participate in the questionnaire survey, data on depressive symptoms were available in 12 158 girls and 9 447 boys. The age ranges from 8.0 to 18.9 years old. Mean age and age range for breast Tanner stage I to Tanner stage V were 8.45 ± 1.56 y (6.0–13.9 y), 10.94 ± 1.68 y (7.4–15.9 y), 13.44 ± 2.14 y (9.3–18.1 y), 15.43 ± 1.89 y (11.0–18.9 y) and 16.32 ± 1.71 y (12.0–18.9 y), respectively. Mean age and age range for genital Tanner stage I to Tanner stage V were 9.26 ± 1.88 y (6.0–14.5 y), 12.32 ± 1.79 y (7.9–16.6 y), 14.37 ± 1.88 y (9.5–18.5 y), 16.32 ± 1.44 y (13.3–18.9 y) and 17.01 ± 1.11 y (14.70–18.9 y), respectively. In boys, about 49.6% and 50.4% are from urban and rural areas, respectively. In girls, about 48.8% and 51.2% are from urban and rural areas, respectively. There is no significant difference in urbanrural area distribution between boys and girls (χ2 = 2.31, P = .129).
VPA and MPA As shown in Table 1, almost one-third of boys had no VPA or MPA during the past week. Compared with boys, no VPA and no MPA participation in girls are even higher (42.8% for VPA; 40.6% for MPA) (χ2 = 278.79, P < .001 for VPA; χ2 = 236.12, P < .001 for MPA). As shown in Figure 1 and Table 1, report rates of VPA or MPA decreased significantly with increase of age and breast Tanner stage among girls. However, in boys, there were no significant decreasing trends of VPA or MPA with age or genital Tanner stage. Figure 1 illustrated change of VPA and MPA report rates with pubertal stage in boys and girls, respectively. It showed that physical activity decreased with pubertal stages except for MPA in boys.
Depressive Symptoms and Its Relation With PA and Pubertal Status The median value of CDI score was 12.27 ± 6.73, with boys scored slightly higher (12.38 ± 6.81) than that among girls (12.18 ± 7.70)
1432
BMI category
Breast /genital Tanner stage
MPA (days/wk)
Total VPA (days/wk)
Factors
1953 (16.7)
V 1868 (15.4)
2738 (23.3)
IV
Overweight
3347 (28.5)
III
10,290 (84.6)
2106 (18.0)
Normal
1586 (13.5)
517 (4.3)
>4
II
1198 (9.9)
3–4
I
5507 (45.3)
514 (4.2)
>4 4936 (40.6)
1203 (9.9)
3–4
1–2
5232 (43.1)
1–2
0
5206 (42.8)
0
12 158
Total n (%)
284 (15.2)
1605 (15.6)
378 (19.4)
486 (17.8)
522 (15.6)
245 (11.6)
194 (12.2)
67 (13.9)
177 (15.5)
679 (12.9)
889(18.6)
78(16.2)
166 (14.5)
590 (11.8)
978(19.4)
1825(15.6)
Depressive n (%)
Girls
0.15
69.49
64.08
110.23
χ2
0.704
