Healthy People 2010 Physical Activity Guidelines and Psychological Symptoms: Evidence From a Large Nationwide Database

Transcription

1 114 Taylor et al. Journal of Physical Activity and Health, 2004, 1, Human Kinetics Publishers, Inc. Healthy People 2010 Physical Activity Guidelines and Psychological Symptoms: Evidence From a Large Nationwide Database Marcus K. Taylor, Ricardo Pietrobon, Deng Pan, Michael Huff, and Laurence D. Higgins Background: Physical inactivity is a risk factor for poor mental health. The present study evaluates the association between mental health and physical activity levels according to the Healthy People 2010 guidelines in a large national sample. Methods: Participants (N = 41,914) were selected from the 2001 Behavioral Risk Factor Surveillance System. Primary predictor variable was physical activity level, and primary outcome measure was frequency of mental distress. Specific outcomes of anxiety and depressive symptoms were also measured. Results: Compared with those meeting the Healthy People 2010 guidelines, sedentary participants were 1.31 times more likely to experience 14 or more days of mental distress during the past 30 days (OR 1.31, 95% CI 1.16, 1.48), 1.34 times more likely to experience anxiety symptoms (OR 1.34, 95% CI 1.21, 1.49), and 1.22 times more likely to experience depressive symptoms (OR 1.22, 95% CI 1.10, 1.36). Comparing those participants falling short of the Healthy People 2010 recommendation with those meeting the guideline, no significant group differences were demonstrated relative to frequency of mental distress. Those meeting the recommendation were more likely to have 14 or more days of anxiety symptoms during the past 30 days (OR 1.10, 95% CI 1.02, 1.17). Conclusions: Our results suggest that being sedentary is clearly associated with more aversive psychological symptoms. However, performing enough physical activity to meet the Healthy People 2010 guideline may not be associated with better psychological status than minimal amounts of physical activity. Key Words: anxiety, depression, mental distress, epidemiology, physical activity M.K. Taylor, R. Pietrobon, and D. Pan are with the Center for Excellence in Surgical Outcomes at Duke University Medical Center, Durham, NC M. Huff is with Michael W. Krzyzewski Human Performance Laboratory at Duke University Medical Center. L.D. Higgins and Pietrobon are with the Division of Orthopedic Surgery at Duke University Medical Center, Durham, NC In addition, Taylor is with the Department of Health and Physical Education, Duke University, Durham, NC

2 Healthy People 2010 Evidence 115 Introduction Growing evidence suggests that physical inactivity is a risk factor for poor mental health, particularly depression, which the World Health Organization has predicted will be second only to cardiovascular disease as the world s leading cause of death and disability by the year Although leading public health agencies have provided physical activity recommendations for the American people, no research has directly examined their associations with psychological outcomes. Healthy People 2010, for example, embodies the national health goals set forth by the U.S. Department of Health and Human Services and includes several objectives that call for increasing levels of physical activity in the U.S. population. 2 This initiative sets forth guidelines for moderate physical activity (at least 30 min, 5 or more days per week) and vigorous physical activity (at least 20 min, 3 or more times per week), and essentially parallels the Surgeon General s physical activity recommendations 3 and the ACSM-CDC physical activity recommendations. 4 The link between these guidelines and psychological status, however, is unexplored. Additionally, although a growing number of epidemiological studies suggest an inverse relationship between physical activity and depression or depressive symptoms, 5 11 the association of less versus more amounts of physical activity to depressive symptoms remains unclear. Furthermore, only one population-based study has demonstrated the connection between physical activity and anxiety symptoms. 5 The present study addresses these deficiencies in the literature. Several cross-sectional and longitudinal epidemiological studies 5 11 have investigated the relationship between physical activity and depression. Assessing four different samples, Stephens 5 reported inverse associations between self-reported physical activity and depression. Similarly, Weyerer, 6 examining a Bavarian population, showed that those who were physically inactive were significantly more likely to have depressive symptoms than those who were regularly active. Interestingly, the odds ratio for those who reported only occasional exercise was also elevated but did not reach statistical significance. In another international sample, Hassmen and colleagues 7 noted that those who exercised less frequently reported greater depressive symptoms than those who exercised regularly. In a prospective design, Farmer et al. 8 showed that women who were sedentary or engaged in little physical activity were more likely to develop depression over an 8- year period compared to those who were moderately active. Similarly, Camacho et al. 11 identified a greater risk of depression for men and women at two follow-up periods (1974 and 1983) if they were inactive at baseline (1965). Additionally, Paffenbarger et al. 9 found that physical activity at baseline was inversely associated with depression 25 years later. Finally, Mobily 10 and colleagues found that men and women reporting more depressive symptoms at baseline, who subsequently became daily walkers, had a greater likelihood of reducing depressive symptoms at a 3-year follow up. Despite an apparent association, then, between a sedentary lifestyle and depression or depressive symptoms, the relationship of less versus more amounts of physical activity and depression or depressive symptoms remains unclear. Unlike the substantial literature addressing physical activity and depression or depressive symptoms, virtually no epidemiological studies have investigated the association between physical activity levels and anxiety or anxiety symptoms. In one exception, Stephens 5 identified more symptoms of anxiety in Canadians reporting little or no physical activity compared to those reporting moderate or

3 116 Taylor et al. very active lifestyles. More research is needed to elucidate not only the association between physical inactivity and anxiety symptoms, but also the role of less versus more amounts of physical activity. The goal of this nationwide investigation was to examine the association between physical activity levels as stated in the Healthy People 2010 guidelines and frequency of mental distress, anxiety symptoms, and depressive symptoms. It was hypothesized that participants meeting the guidelines for either moderate or vigorous physical activity (30 min of moderate physical activity for at least 5 days per week, or 20 min of vigorous physical activity for at least 3 days per week) would have a lower risk of mental distress, anxiety symptoms, and depressive symptoms compared to physically inactive participants. It was further expected that those meeting the recommendation would demonstrate a decreased risk of mental distress, anxiety symptoms, and depressive symptoms compared to those engaging in some physical activity but not reaching the recommended physical activity level. Study Population Methods Patients were selected from the 2001 Behavioral Risk Factor Surveillance System (BRFSS), which is conducted in all 50 states, the District of Columbia, Guam, Puerto Rico, and the Virgin Islands. The BRFSS is a population based, randomdigit dialed telephone survey of the civilian, non-institutionalized U.S. population, aged 18 years and older. In a comprehensive review of studies examining the psychometric properties of the BRFSS from 1993 to 2000, Nelson et al. 12 report at least moderate reliability and validity for most elements of the BRFSS survey, many of which were highly reliable and valid. The total sample size for the present study was 41,914, and the response rate was 51.1%. The sample was weighted and post stratified to adjust the distribution of data to accurately reflect the total population of the U.S. No exclusion criteria were implemented for this study. Main Effect Measure Leisure-Time Physical Activity. In the BRFSS 2001, participants are told, We are interested in two types of physical activity: vigorous and moderate. Vigorous activities cause large increases in breathing or heart rate while moderate activities cause small increases in breathing or heart rate. Relative to moderate physical activity, participants are asked, Thinking about the moderate physical activities you do (when you are not working) in a usual week, do you do moderate activities for at least 10 minutes at a time, such as brisk walking, bicycling, vacuuming, gardening, or anything else that causes small increases in breathing or heart rate? Follow-up questions include, How many days per week do you do these moderate activities for at least 10 minutes at a time? and On days when you do moderate activities for at least 10 minutes at a time, how much total time per day do you spend doing these activities? Relative to vigorous physical activity, participants are asked, Now thinking about the vigorous physical activities you do (when you are not working) in a usual week, do you do vigorous activities for at least 10 minutes at a time, such as running, aerobics, heavy yard work, or anything else

4 Healthy People 2010 Evidence 117 that causes large increases in breathing or heart rate? Similar follow-up questions are asked regarding vigorous physical activity. Three studies have examined the reliability of the BRFSS physical activity questions Shea et al. 13 assessed reliability for engaging in no physical activity in the past month, and k values ranged from.57 to.77. Additionally, Stein and colleagues 14 examined the reliability for engaging in no physical activity and regular participation in vigorous physical activity. For sedentary lifestyle, k values ranged from.50 to.63. For vigorous physical activity, k values varied by race:.61 for Whites,.64 for Hispanics, and.07 for Blacks. Finally, Brownson and colleagues 15 found that, among women aged 40 or older, k values ranged from.26 to.30 for moderate or vigorous physical activity. No specific studies have investigated the validity of BRFSS physical activity questions, although two physical activity survey instruments the Minnesota Leisure Time Physical Activity Survey and the Harvard Alumni Activity Survey are similar to the BRFSS questions, and moderately correlate to several physiologic, biochemical, and diary recalls. 16,17 Both instruments reportedly distinguish sedentary from non-sedentary people, and adequately determine vigorous but not moderate physical activity. 12 Finally, Dishman et al. 18 assert that no single gold standard exists for judging the validity of physical activity measures, and the methods chosen to assess physical activity may vary according to the nature of the research question being addressed. Outcome Measures Frequency of Mental Distress. Participants were asked for how many days out of the past 30 days had their mental health not been good, including stress, depression, and problems with emotions. Acceptable concurrent validity is reported for this measure, as it correlates significantly in a general population comparison with the widely used and clinically validated Medical Outcomes Study Short Form 36 (SF-36) 19,20, including the Mental Health, Role Emotional, and Mental Component summary scales. Significant correlations have also been demonstrated with the Center for Epidemiological Studies of Depression Scale in a study of elder, lowincome black males, 21,22 although there is disagreement about the underlying structure of the CES-D. 23 Finally, large differences in frequency of mental distress across socioeconomic and demographic groups 24 demonstrates preliminary evidence for construct validity of this measure, although additional research is needed to more fully establish construct validity. Participants were classified according to whether their mental health, as measured by frequency of mental distress, anxiety, and depressive symptoms, was not good for 14 or more days of the preceding 30 days. This 14-day period was selected because clinicians and clinical researchers often use a similar period as a marker for clinical depression and anxiety disorders, 25 being in agreement with previous research using these measures. 26,27 To further characterize mental health status, specific questions were also asked about days of recent anxiety and depressive symptoms, respectively. Frequency of Anxiety Symptoms. Patients were asked for how many days out of the past 30 days they had felt worried, tense, or anxious. Frequency of Depressive Symptoms. Patients were asked for how many days out of the past 30 days they had felt sad, blue, or depressed.

5 118 Taylor et al. Sensitivity analyses to evaluate the robustness of the models were also performed by changing the threshold number of days with each psychological symptom from 14 days to 10 and 20 days, respectively. Stratified Analysis of Outcomes We assessed the association between leisure-time physical activity and risk-adjusted psychological symptoms in stratified analyses for patients years, years, and greater than 60 years of age. Stratified analyses were conducted because age has been suggested to substantially affect the relationship between physical activity and mental health outcomes. 28 Covariates The primary predictor variable in the present investigation was prevalence of leisure-time physical activity. Other covariates included age (18 40 years, years, 60 years and older), gender, race (white, black, other), education (no college education, 1 4 years of college), household income (0 to 34,999 USD; 35,000 USD or more), perceived general health (excellent, very good, good, fair, poor, don t know), perceived physical health (number of days during past 30 in which physical health was not good: 10 days or less, days, days), activity limitations due to health problems, and time of year (December February, March November) when the participant completed the survey as the winter months may affect both physical activity levels and mental health symptoms. Statistics All statistical analyses were performed using Stata version 8.0 for Linux (Stata Corp., College Station, TX, USA). Since the BRFSS database is a stratified probability sample, calculations were adjusted for survey sampling weights. The following factors were used in defining the probability weights for sampling: subsets of area code/prefix combinations, inverse of the number of residential telephone numbers in the respondent s household, the number of adults in the respondent s household, the number of people in an Age-by-Sex or Age-by-Race/Ethnicity-by- Sex category in the population of a region or a state. Initially, descriptive analyses were performed using means and percentages with 95% confidence intervals. The crude association between physical activity level and each of the outcomes was measured using t tests and chi-square tests. Risk-adjusted association between physical activity level and each of the outcomes was further evaluated using logistic regression models adjusted for age, race, gender, income, education, general and physical health, activity limitations due to health problems, and time of year in which the participant completed the survey. The analyses were also stratified by age (18 40 years, years, and 60+ years). Baseline Characteristics Results The database contains information about 41,914 participants (Table 1); 16,781 participants (40.04%) were years old, 18,917 (45.13%) were years

6 Healthy People 2010 Evidence 119 Table 1 Participants Demographics Meet Less than Physically Variable recommendation recommendation inactive p value Age ,111 (50.29%) 6,168 (38.25%) 1,847 (11.45%) ,927 (44.36%) 7,377 (41.29%) 2,564 (6.97%) > 60 1,972 (38.09%) 1,919 (37.07%) 1,286 (24.84%) Race White 14, 608 (47.36%) 12,230 (39.65%) 4,007 (12.99%) Black 1,767 (37.51%) 1,883 (39.97%) 1,061 (22.52%) Other 1,592 (45.09%) 1,312 (37.16%) 627 (17.76%) Gender Male 8,133 (49.50%) 6,065 (36.91%) 2,232 (13.58%) Female 10,050 (43.51%) 9,516 (41.19%) 3,534 (15.30%) Education No college 6,197 (40.88%) 5,680 (37.47%) 3,283 (21.66%) College 11,960 (49.20%) 9,884 (40.66) 2,464 (10.14%) Household income < 35,000 5,529 (41.31%) 5,115 (38.21%) 2,741 (20.48%) 35,000 10,574 (50.17%) 8,597 (40.79%) 1,907 (9.05%) General health Excellent 5,496 (57.62%) 3,217 (33.72%) 826 (8.66%) Very good 6,750 (48.12%) 5,892 (42.01%) 1,384 (9.87%) Good 4,329 (40.10%) 4,604 (42.65%) 1,863 (17.26%) Fair 1,301 (34.82%) 1,417 (37.93%) 1,018 (27.25%) Poor 283 (20.76%) 424 (31.11%) 656 (48.13%) Physical health < 10 days 16,794 (47.56%) 14,108 (39.95%) 4,409 (12.49%) days 525 (38.04%) 532 (38.55%) 323 (23.41%) days 748 (30.53%) 796 (32.49%) 906 (36.98%) Activity limitation No 15,910 (47.77%) 13,219 (39.69%) 4,176 (12.54%) Yes 2,241 (36.45%) 2,335 (37.98%) 1,572 (25.57%) Time of year Winter 3,569 (43.99%) 3,233 (39.84%) 1,312 (16.17%) Other 14,614 (46.52%) 12,368 (39.37%) 4,454 (14.18%) <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001

7 120 Taylor et al. old, and 5,785 (13%) were older than 60 years. Participants were predominately White (78.26%), and consisted of slightly more females than males (51.45%). Most of the participants (n = 25,433, 58.73%) had attended at least 1 year of college, and 21,895 (62.66%) reported a household income of 35,000 or more. Approximately one third described their general health as very good (n = 14,791, 35.85%), while 11,561 (27.57%) described their general health as good, and 11,561 (27.57%) described their general health as fair. A large majority of participants (37,335, 90.81%) reported 10 or fewer days of poor physical health of the last 30 days, and only 6,563 (14.93%) reported activity limitation due to health problems. Finally, 8,628 (20.10%) completed the BRFSS survey during the winter months. Leisure-Time Physical Activity The largest proportion of participants (n = 18,183, 45.98%) met or exceeded the Healthy People 2010 public health recommendations for moderate or vigorous physical activity, while 15,581 (39.31%) engaged in some physical activity but fell short of the recommended value. Finally, 5,766 (14.70%) were physically inactive. When vigorous physical activity was considered independently, 10,357 participants (24.71%) met or exceeded the Healthy People 2010 public health recommendations for vigorous physical activity, while 7,664 (18.24%) engaged in some physical activity but fell short of the recommended value, and 23,435 (55.91%) did not participate in any vigorous physical activity. Psychological Symptoms The majority of participants (n = 31,226, 74.46%) reported 14 or more days of mental distress during the last 30 days. Relative to frequency of anxiety symptoms, 23,523 (56.04%) reported 14 or more days during the last 30 days. Finally, 27,080 participants (65.13%) reported 14 or more days of depressive symptoms during the last 30 days. Leisure-Time Physical Activity and Mental Health Across all three psychological variables, a larger percentage of physically inactive participants consistently experienced greater than 14 days of mental distress (81.3%), anxiety symptoms (66.9%), and depressive symptoms (70.3%), as compared to participants meeting the recommendation and those doing some physical activity but not meeting the recommendation. A slightly higher percentage of those participants meeting the Healthy People 2010 physical activity recommendation experienced greater than 14 days of mental distress (73.4%), anxiety symptoms (54.6%), and depressive symptoms (62.2%), as compared to those doing some physical activity but less than the recommended amount. Robustness of these models was demonstrated, as similar patterns emerged when the threshold number of days with each psychological symptom was changed to 10 days and 20 days (Table 2). Meeting the Recommendation Versus Physical Inactivity Risk Adjusted Endpoints. Compared with participants meeting the Healthy People 2010 guidelines, physically inactive participants were 1.31 times more likely to have at least 14 days of mental distress in the past 30 days (OR 1.31, 95% CI

8 Healthy People 2010 Evidence 121 Table 2 Leisure-Time Physical Activity and Mental Health Outcomes Psychological symptom / Meet Less than Physically criteria (days) recommendation recommendation inactive p value Mental distress 10 13,813 (75.97%) 11,690 (75.03%) 4,862 (84.32%) < ,345 (73.40%) 11,242 (72.15%) 4,685 (81.25%) < ,801 (70.40%) 10,727 (68.85%) 4,456 (77.28%) <.0001 Anxiety 10 10, 858 (57.72%) 9,039 (58.01%) 4,124 (71.52%) < ,932 (54.62%) 8,158 (52.36%) 3,856 (66.87%) < ,040 (48.05%) 7,425 (47.65%) 3,557 (61.69%) <.0001 Depression 10 12,263 (65.18%) 10,104 (64.85%) 4,248 (73.67%) < ,705 (62.22%) 9,617 (61.72%) 4,052 (70.27%) < ,177 (61.47%) 9,113 (58.49%) 3,816 (66.18%) < , 1.48), 1.34 times more likely to have at least 14 days of anxiety symptoms (OR 1.34, 95% CI 1.21, 1.49), and 1.22 times more likely to have 14 or more days of depressive symptoms (OR 1.22, 95% CI 1.10, 1.36; Table 3). Again, robustness of these models was demonstrated when the threshold number of days with each psychological symptom was changed to 10 days and 20 days. Endpoints Stratified By Age. In participants years old (Table 3), significant differences remained between those meeting the recommendation and physically inactive participants, with physically inactive participants demonstrating more aversive outcomes across all three measures (mental distress, anxiety symptoms, depressive symptoms). In participants years old, similar group differences were shown relative to mental distress, with physically inactive participants being 1.20 times more likely to experience 14 or more days during the past 30 days (OR 1.20, 95% CI 1.00, 1.44) than those meeting the Healthy People 2010 guidelines (Table 3). Significant results remained when the threshold number of days with mental distress was changed to 10, but not 20, days. Furthermore, in this age strata, physically inactive participants demonstrated greater risk for the specific measure of anxiety symptoms (OR 1.24, 95% CI 1.07, 1.43) but not depressive symptoms. Finally, in participants older than 60 years, a sedentary lifestyle was associated with an increased risk of mental distress, according to two of three indices. In this population, no significant group differences were shown relative to the specific measures of anxiety or depressive symptoms. Meeting the Recommendation Versus Some Physical Activity Risk Adjusted Endpoints. In a comparison of participants doing some physical activity but not meeting the Healthy People 2010 recommendation versus partici-

9 122 Taylor et al. Table 3 Risk Adjusted Odds Ratios (95% CI) Stratified By Age: Meeting Healthy People 2010 Recommendation Versus Physically Inactive Psychological symptom / criteria Overall (days) population yr yr >60 yr Mental distress (1.25, 1.59) 1.47 (1.23, 1.75) 1.34 (1.12, 1.64) 1.46 (1.00, 2.15) (1.16, 1.48) 1.40 (1.18, 1.67) 1.20 (1.00, 1.44) 1.40 (0.97, 2.03) (1.14, 1.43) 1.38 (1.16, 1.63) 1.15 (0.96, 1.36) 1.41 (1.00, 1.98) Anxiety (1.22, 1.51) 1.52 (1.28, 1.81) 1.28 (1.10, 1.49) 1.16 (0.86, 1.56) (1.21, 1.49) 1.50 (1.27, 1.78) 1.24 (1.07, 1.43) 1.25 (0.93, 1.67) (1.22, 1.51) 1.50 (1.26, 1.78) 1.26 (1.09, 1.46) 1.28 (0.97, 1.70) Depression (1.07, 1.35) 1.40 (1.18, 1.67) 1.05 (0.90, 1.23) 1.23 (0.89, 1.70) (1.10, 1.36) 1.45 (1.22, 1.72) 1.04 (0.89, 1.21) 1.25 (0.91, 1.71) (1.08, 1.32) 1.40 (1.19, 1.65) 1.02 (0.88, 1.18) 1.28 (0.94, 1.74) Note. Risk adjustment for age, race, gender, education, household income, perceived general health, perceived physical health, activity limitations due to health problems, and time of year (season) in which data were collected. pants meeting the recommendation, no significant group differences were demonstrated in relation to frequency of mental distress. Those meeting the recommended guideline, however, were more likely to have at least 14 days of anxiety symptoms of the past 30 days (OR 1.10, 95% CI 1.02, 1.17). Those meeting the recommendation were also at greater risk of depressive symptoms, according to two of three indices (Table 4). Endpoints Stratified By Age. Across all three age strata, no significant differences were revealed between participants meeting the recommendation and those doing less than the recommended amount relative to mental distress (Table 4). In the year-old group, those meeting the recommendation were more likely to have experienced 14 or more days of anxiety symptoms during the past 30 days (OR % CI 1.03, 1.25), and this relationship persisted across two of the three indices. In this population, robust findings demonstrated greater risk among those meeting the Healthy People 2010 recommendation relative to the specific measure of depressive symptoms. In participants greater than 60 years of age, those meeting the Healthy People 2010 physical activity recommendation exhibited greater risk of having more than 14 days of anxiety symptoms (OR % CI 1.09,1.71), compared to those doing less than the recommended value (Table 4). In this age strata, such group differences did not prevail relative to mental distress or the specific measure of depressive symptoms.

10 Healthy People 2010 Evidence 123 Table 4 Risk Adjusted Odds Ratios (95% CI) Stratified By Age: Some Physical Activity But Not Meeting Healthy People 2010 Recommendation Versus Meeting Recommendation Psychological symptom / criteria Overall (days) population yr yr >60 yr Mental distress (0.98, 1.14) 1.08 (0.96, 1.20) 1.01 (0.90, 1.14) 1.16 (0.82, 1.62) (0.99, 1.15) 1.05 (0.94, 1.17) 1.07 (0.96, 1.19) 1.24 (0.89, 1.72) (0.97, 1.13) 1.00 (0.90, 1.11) 1.09 (0.98, 1.21) 1.21 (0.89, 1.04) Anxiety (1.01, 1.16) 1.04 (0.94, 1.14) 1.10 (0.99, 1.21) 1.33 (1.05, 1.68) (1.02, 1.17) 1.03 (0.94, 1.14) 1.13 (1.05, 1.25) 1.36 (1.09, 1.71) (1.01, 1.15) 1.01 (0.91, 1.12) 1.11 (1.01, 1.22) 1.33 (1.06, 1.66) Depression (1.01, 1.17) 1.06 (0.95, 1.19) 1.13 (1.02, 1.26) 1.04 (0.81, 1.33) (0.99, 1.15) 1.02 (0.92, 1.14) 1.11 (1.01, 1.24) 1.14 (0.90, 1.45) (1.00, 1.16) 1.02 (0.92, 1.14) 1.14 (1.03, 1.26) 1.09 (0.86, 1.38) Note. Risk adjustment for age, race, gender, education, household income, perceived general health, perceived physical health, activity limitations due to health problems, and time of year (season) in which data were collected. Additional analyses compared groups relative to vigorous physical activity only, rather than moderate or vigorous physical activity. The results are summarized here. Vigorous Physical Activity Versus Physical Inactivity Risk Adjusted Endpoints. Participants who did not participate in any vigorous physical activity were more likely to have experienced 14 or more days of mental distress (OR % CI 1.11, 1.34), anxiety symptoms (OR % CI 1.17, 1.37), and depressive symptoms (OR % CI 1.08, 1.27) in the past 30 days, compared to those participants meeting the vigorous physical activity recommendation. Robustness of each of these findings was demonstrated. Endpoints Stratified By Age. In participants years old, physical inactivity was associated with a greater risk of mental distress (OR % CI 1.07, 1.39), anxiety symptoms (OR % CI 1.18, 1.48), and depressive symptoms (OR % CI 1.09, 1.38). Similar group differences where shown in the year old population in terms of mental distress (OR % CI 1.04, 1.39) and anxiety symptoms (OR % CI 1.09, 1.38), but not depressive symptoms. Finally, in participants greater than 60 years of age, no differences emerged between those meeting the Healthy People 2010 vigorous physical activity recommendation

11 124 Taylor et al. Table 5 Risk Adjusted Odds Ratios (95% CI) Stratified By Age: Meeting Healthy People 2010 Vigorous Physical Activity Recommendation Versus No Vigorous Physical Activity Psychological symptom / criteria Overall (days) population yr yr >60 yr Mental distress (1.11, 1.33) 1.20 (1.06, 1.36) 1.25 (1.08, 1.44) 0.90 (0.56, 1.44) (1.11, 1.34) 1.22 (1.07, 1.39) 1.20 (1.04, 1.39) 1.01 (0.65, 1.55) (1.12, 1.35) 1.23 (1.08, 1.39) 1.22 (1.07, 1.41) 1.04 (0.69, 1.57) Anxiety (1.16, 1.35) 1.31 (1.17, 1.47) 1.22 (1.08, 1.38) 0.84 (0.62, 1.15) (1.17, 1.37) 1.32 (1.18, 1.48) 1.22 (1.09, 1.38) 0.88 (0.64, 1.20) (1.19, 1.39) 1.33 (1.18, 1.50) 1.26 (1.12, 1.42) 0.93 (0.69, 1.25) Depression (1.07, 1.26) 1.21 (1.07, 1.36) 1.09 (0.96, 1.23) 1.20 (0.87, 1.67) (1.08, 1.27) 1.22 (1.09, 1.38) 1.11 (0.99, 1.26) 1.15 (0.83, 1.60) (1.09, 1.27) 1.23 (1.09, 1.38) 1.10 (0.98, 1.24) 1.24 (0.90, 1.70) Note. Risk adjustment for age, race, gender, education, household income, perceived general health, perceived physical health, activity limitations due to health problems, and time of year (season) in which data were collected. and sedentary participants in terms of mental distress, anxiety symptoms, or depressive symptoms. Meeting the Recommendation Versus Some Vigorous Physical Activity Risk Adjusted Endpoints. Relative to mental distress and depressive symptoms, no significant differences were shown between those performing less than the recommended amount of vigorous physical activity and those meeting the recommendations. Robust findings indicated that participants meeting the vigorous physical activity recommendation are at greater risk of anxiety symptoms (OR 1.13, 95% CI 1.03, 1.24; Table 6). Endpoints Stratified By Age. Across all three age categories, no significant differences were revealed between participants meeting the vigorous physical activity recommendation and those doing less than the recommended amount relative to mental distress or depressive symptoms. In the year-old group, those meeting the vigorous physical activity recommendation were more likely to have experienced 14 or more days of anxiety symptoms during the past 30 days (OR % CI 1.10, 1.46), a relationship that prevailed across all three indices.

12 Healthy People 2010 Evidence 125 Table 6 Risk Adjusted Odds Ratios (95% CI) Stratified By Age: Some Vigorous Physical Activity But Not Meeting Healthy People 2010 Recommendation Versus Meeting Vigorous Physical Activity Recommendation Psychological symptom / criteria Overall (days) population yr yr >60 yr Mental Distress (0.87, 1.08) 0.96 (0.83, 1.10) 0.97 (0.82, 1.16) 1.34 (0.76, 2.39) (0.85, 1.06) 0.91 (0.79, 1.05) 1.00 (0.84, 1.19) 1.34 (0.80, 2.25) (0.85, 1.05) 0.89 (0.78, 1.03) 1.00 (0.84, 1.18) 1.31 (0.80, 2.14) Anxiety (1.02, 1.24) 1.05 (0.92, 1.21) 1.25 (1.08, 1.44) 1.23 (0.82, 1.84) (1.03, 1.24) 1.05 (0.92, 1.19) 1.27 (1.10, 1.46) 1.24 (0.83, 1.86) (1.03, 1.23) 1.08 (0.95, 1.24) 1.22 (1.06, 1.40) 1.11 (0.74, 1.66) Depression (0.97, 1.18) 1.05 (0.91, 1.20) 1.11 (0.96, 1.29) 1.03 (0.67, 1.58) (0.94, 1.15) 1.01 (0.88, 1.16) 1.08 (0.94, 1.26) 1.07 (0.70, 1.64) (0.93, 1.14) 1.01 (0.88, 1.16) 1.06 (0.91, 1.23) 1.05 (0.69, 1.60) Note. Risk adjustment for age, race, gender, education, household income, perceived general health, perceived physical health, activity limitations due to health problems, and time of year (season) in which data were collected. Discussion The present study contributes to the literature in at least three ways. To begin, this is the first analysis linking public health recommendations for physical activity to psychological status in a nationwide database. Additionally, although several epidemiological studies report an inverse relationship between physical activity and depression or depressive symptoms, few studies have compared more versus less amounts of physical activity, with equivocal findings. Moreover, this is only the second epidemiological study to examine the link between physical activity and anxiety symptoms. The present findings suggest that, compared with those meeting the Healthy People 2010 guidelines, physically inactive Americans are more likely to have 14 or more days of mental distress in the past 30 days (OR % CI 1.16, 1.48), a pattern that was somewhat consistent across age strata. A comparison of those doing less than the recommended amount versus those meeting the recommendation, however, yielded a robust pattern of greater risk of anxiety symptoms among those performing the recommended value (OR % CI 1.02, 1.17). In age-stratified analyses, similar patterns emerged in the years old group and those 60 years and older, but not in the year-old group. In this investigation, physical inactivity was associated with a greater risk of mental distress compared to physical activity levels meeting the Healthy People

13 126 Taylor et al guidelines. Similar patterns of group differences emerged relative to anxiety and depressive symptoms. Although at least 25 population-based studies in the past 15 years have examined the relationship between physical activity and depression or depressive symptoms, the findings remain equivocal. Several psychosocial (e.g., improved self-image, feelings of control, social support), as well as neurobiological explanations (e.g., increased synthesis of monoamines) have been advanced to explain possible antidepressant effects of physical activity, but conclusive evidence awaits further research. Although a sedentary lifestyle was associated with a significantly greater risk of mental distress, anxiety symptoms and depressive symptoms compared to those meeting the physical activity recommendation in the general population and in younger adults, these patterns did not persist for the specific measures of anxiety and depressive symptoms in the older age-group categories (Table 3). Specifically, no group differences surfaced relative to anxiety symptoms in participants over 60 years of age, and no group differences in depressive symptoms appeared in the or the 60+ categories. With regard to depressive symptoms, this finding supports previous work, 28 suggesting that the benefits of reduced depressive symptoms may diminish as people age. The present investigation suggests similar age-related changes associated with anxiety symptoms, at least beyond 60 years of age. More research, however, is needed to better characterize age-related changes in the physical activity anxiety/depression relationship. Comparing the psychological symptoms of those doing some physical activity yet falling short of the recommendation versus those meeting the Healthy People 2010 recommendation, no significant group differences were seen relative to mental distress. A robust pattern, though, demonstrated significantly greater risk of anxiety symptoms in the more active participants, a finding that persisted in the older segments of the population, but not in the age group. This finding must be considered in light of a large body of literature demonstrating anxiolytic effects of acute exercise 29,30 as well as reductions in trait anxiety after exercise training. 30 However, it is also important to determine how much physical activity is minimally or optimally necessary to protect against aversive psychological symptoms. Presently, there is disagreement regarding dose-response between intensity or amount of physical activity and both anxiety and depressive symptoms. 31,32 For example, in the Canada Fitness Survey, 5 people reported fewer symptoms of depression if their daily leisure energy expenditure was at least 1 kcal/kg body weight per day, which is a low level of physical activity (about 20 min of walking). Risk of depression was not further reduced when the energy expenditure was raised to 2 kcal/kg body weight per day. Conversely, data from the Harvard Alumni study 9 did suggest a dose-response reduction in depression with increasing levels of exercise. Specifically, this relationship prevailed through more than 3 hours of sporting activities per week or 2500 kcal per week. As noted earlier, only one populationbased study has examined the physical activity-anxiety relationship, and does not suggest additional benefits associated with increasing levels of physical activity. In the present study, it is suggested that, although being sedentary is associated with more aversive psychological symptoms, performing enough physical activity to meet or exceed the Healthy People 2010 recommendation may not be more protective than lower levels of physical activity (Table 4). Furthermore, the present findings may relate to previous literature demonstrating that excessive training in athletics (i.e., overtraining) induces mood disturbance in some athletes, 33,34 although

14 Healthy People 2010 Evidence 127 most people do not engage in the same levels of physical activity as competitive sports performers. Alternatively, it is also conceivable that a number of confounding variables not considered in our study may explain the higher levels of anxiety symptoms in those performing the recommended levels of physical activity. Finally, as in the case of depression, both psychosocial explanations (e.g., distraction from worrisome thoughts, social support, increased self-esteem) as well as neurobiological explanations (e.g., increased seratonin synthesis; 35) have been proposed to explain possible anxiolytic effects of physical activity, although conclusive mechanistic explanations are presently unavailable. Similarly, the possibility that physical activity levels in accordance with the Healthy People 2010 recommendations may be associated with greater anxiety symptoms, especially in older adults, is an important issue that warrants further investigation. Further group comparisons were performed examining only vigorous physical activity. Looking at the comparison of participants meeting the Healthy People 2010 recommendation for vigorous physical activity to sedentary participants (Table 5), striking similarities are noted in relation to the comparison of these two groups relative to either moderate or vigorous physical activity (Table 3). Likewise, group comparisons of those performing less than the recommended amount versus those meeting the physical activity guidelines for vigorous physical activity (Table 6) yielded similar patterns of psychological symptoms as the earlier comparison which considered either moderate or vigorous physical activity (Table 4). In sum, it appears that similar psychological outcomes may be associated with physical activity levels according to the Healthy People 2010 recommendations, regardless of whether moderate and vigorous physical activity are considered together, or if vigorous physical activity is examined independently. We would like to acknowledge the limitations of our study. To begin, it should be noted that the percentages of participants reporting mental distress, anxiety symptoms, and depressive symptoms were quite high (see Table 2), leading one to question the extent to which the BRFSS questions measuring these constructs tap clinical or subclinical levels of anxiety and depression. Also, although the BRFSS is described as one of the most important measures of leisure time physical activity in the United States, 4 the validity of the BRFSS physical activity items is based on other studies with similar questions measuring physical activity. Furthermore, while previous psychometric research suggests concurrent validity of the primary outcome measure (mental distress), firm establishment of construct validity of this measure awaits further research. Moreover, behavioral artifacts such as response distortion can potentially influence self-report measures of this type. Additionally, the validity of the specific measures of anxiety and depressive symptoms has not been established. Also, it should be noted that all psychological variables were measured by a single question, prompting us to test robustness of all models with multiple thresholds. Another important limitation is that all associations between physical activity and psychological symptoms in the present study are cross-sectional. Although a few prospective population-based studies have shown that physical activity levels predict people s depression or depressive symptoms over time, 8,9,11 the possibility remains that people become less active after experiencing poor mental health, rather than experiencing poor mental health as a result of being physically inactive. In the same respect, it is possible that those who experience more positive psychological symptoms are more likely to begin exercising or become more physically active, rather than the exercise or physical activity conferring positive

15 128 Taylor et al. psychological benefits. Additionally, it should be recognized that the BRFSS does not measure clinical levels of anxiety or depression, and should not be interpreted in this manner. Finally, although the BRFSS 2001 does measure physical activity at work, we were unable to assess this variable as a possible confounder, because of a large proportion of missing data. We are therefore examining psychological outcomes of leisure-time physical activity, although 17% of the population reported doing some level of physical activity at work. Despite the above-mentioned drawbacks, the present investigation has numerous strengths. First, the sample size is quite large, allowing us to reach conclusions with great confidence. Additionally, the findings are representative of the entire civilian, non-institutionalized U.S. population 18 years of age and older. Population-based studies may have certain advantages over randomized controlled trials in that they better represent a heterogeneous population under real-life conditions, and thus possess greater external validity. 36 In sum, this study was conducted because the link between leading public health agencies physical activity recommendations and psychological status is not well understood, few population-based studies have compared varying amounts of physical activity relative to depressive symptoms, and only one published epidemiological study has investigated the link between physical activity and anxiety symptoms. Our results suggests that, although a sedentary lifestyle is associated with adverse psychological symptoms, meeting the Healthy People 2010 recommendations for physical activity may not be advantageous to performing physical activity below the recommended value. In simple terms, it appears that some is better than none, but more is not necessarily better than some. Future research should continue to elucidate the psychological outcomes of leading public health physical activity recommendations, as well as quantify the physical activity stimulus necessary to promote optimal mental health. References 1. Saraceno B. The WHO World Health Report on mental health. Epidemiologia e Psichiatria Sociale, 2002;11(2): U.S. Department of Health and Human Services. Healthy People 2010, Volume II, Conference Edition. Atlanta, Ga: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion; U.S. Department of Health and Human Services. Physical Activity and Health: A Report of the Surgeon General. Atlanta, Ga: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion; Brownson RC, Jones DA, Pratt M, Blanton C, Heath G. Measuring physical activity with the behavioral risk factor surveillance system. Med Sci Sports Exerc. 2000;32: Stephens T. Physical activity and mental health in the United States and Canada: evidence from four population surveys. Prev Med. 1988;17: Weyerer S. Physical inactivity and depression in the community. Evidence from the Upper Bavarian Field Study. Int J Sports Med. 1992;13: Hassmen P, Koivula N, Uutela A. Physical exercise and psychological well-being: a population study. Prev Med. 2000;30:17-25.

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