Total and Leisure-Time Walking Among U.S. Adults

Total and Leisure-Time Walking Among U.S. Adults Should Every Step Count? Janet H. Bates, MD, MPH, Mary K. Serdula, MD, MPH, Laura Kettel Khan, PhD, Deborah A. Jones, PhD, Cathleen Gillespie, MS, Barbara E. Ainsworth, PhD, MPH Background: Although walking is a popular leisure-time activity, a substantial amount of total daily walking occurs in nonleisure contexts (i.e., occupation, transportation, and household work). Because nonleisure walking is not assessed by traditional leisure-time activity surveys, total walking among U.S. adults may be underestimated. This study describes walking estimates obtained from a measure of leisure-time activity and a specific measure of total walking in all contexts. Methods:

A national sample of adults (n ⫽6626), selected by random-digit dialing, was surveyed between May 1999 and November 2000. Estimates of walking prevalence and of weekly time spent walking were examined from two separate modules: (1) an assessment restricted to leisure-time activity, and (2) an assessment of total walking.

Results:

Walking prevalence based on the total walking module was nearly double that based on the leisure-time module (81% vs 43%, respectively). The median weekly minutes of walking also nearly doubled using the total walking module (239 vs 130 minutes, respectively). Among those with jobs involving substantial walking, median weekly walking minutes were more than three times greater with the total walking module (476 vs 130 minutes, respectively).

Conclusions: U.S. adults, particularly those with jobs involving walking, do a substantial amount of walking not captured by traditional leisure-time activity surveys. This may affect the appropriate targeting of physical activity interventions, as well as the evaluation of the effectiveness of physical activity promotions and policies. However, further characterization of nonleisure walking is needed to determine its contribution to health and meeting physical activity guidelines. (Am J Prev Med 2005;29(1):46 –50) © 2005 American Journal of Preventive Medicine

Introduction

P

hysical activity surveillance is important for guiding public health action and evaluating the effectiveness of activity promotion policies and programs.1 Such programs commonly encourage regular walking, which reduces chronic disease morbidity and mortality,2–13 and has broad appeal among U.S. adults as a popular leisure-time physical activity.14 –16 However, much daily walking occurs in nonleisure contexts (i.e., occupation, transportation, and household)17,18 that is not captured by traditional leisure-time activity From the Epidemic Intelligence Service, Division of Applied Public Health Training, Epidemiology Program Office (Bates), Chronic Disease Nutrition Branch, Division of Nutrition and Physical Activity (Serdula, Kettel Kahn, Gillespie), and Physical Activity and Health Branch, Division of Nutrition and Physical Activity (Jones), National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia; and Department of Exercise Science and Nutritional Sciences, San Diego State University (Ainsworth), San Diego, California Address correspondence and reprints requests to: Janet Bates, MD, MPH, Medical Epidemiologist, California Cancer Registry, Cancer Surveillance Section, 1700 Tribute Road, Suite 100, Sacramento CA 95815. E-mail: [email protected].

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surveys. There is evidence from small studies of population subgroups that leisure-time activity surveys underestimate total walking prevalence.19,20 This lack of data on nonleisure activity has been recognized as a gap in physical activity surveillance.21–24 Accurate walking estimates are needed to appropriately target activity messages and interventions and to measure their effectiveness. The National Physical Activity Survey (NPAS) collected information on walking in all settings as well as activity restricted to leisure time. This study describes the estimated prevalence of walking among U.S. adults using two separate survey modules contained within the NPAS: (1) a specific module for total walking (leisure and non-leisure); and (2) the leisure-time physical activity module from the state-based Behavioral Risk Factor Surveillance System (BRFSS).25

Methods Design The NPAS has been previously described.26 Briefly, it is a cross-sectional, national random-digit-dial survey conducted

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0749-3797/05/$–see front matter doi:10.1016/j.amepre.2005.03.011

Table 1. Percentage of adults who perform any walking as measured by NPAS leisure-time and total walking modules Leisure-time activity module

Total Gender Male Female Age (years) 18–34 35–44 45–54 55–64 ⱖ65 Race/ethnicity Non-Hispanic white Non-Hispanic black Hispanic Other Education College graduate Some college High school graduate ⬍High school Work activity Sedentary job Walking job Heavy labor job Not employed

Total walking module

Prevalence differencea

n

%

95% CI

%

95% CI

%

6626

42.9

41.2–44.5

80.5

79.3–81.7

37.6

2711 3915

33.5 51.7

31.1–36.0 49.7–53.7

80.2 80.8

78.2–82.2 79.3–82.2

46.7 29.1

2033 1625 1223 781 964

34.2 42.5 46.3 52.4 49.8

31.2–37.2 39.1–45.8 42.8–49.7 48.3–56.4 46.1–53.6

84.6 82.4 81.3 77.6 71.3

82.4–86.8 80.0–84.8 78.8–83.8 74.3–80.9 67.9–74.7

50.4 39.9 35.0 25.2 21.5

5191 710 497 228

43.4 38.6 42.8 42.9

41.9–44.9 34.3–42.9 30.1–55.6 22.8–63.0

80.0 78.0 86.9 90.0

78.8–81.2 74.2–81.8 79.1–94.7 83.5–96.5

36.6 39.4 44.1 47.1

2143 1930 2002 551

44.1 45.4 42.8 31.0

41.1–47.0 42.5–48.4 40.1–45.6 25.4–36.5

81.4 82.3 80.2 72.5

79.4–83.5 80.2–84.3 78.1–82.4 66.5–78.5

37.3 36.9 37.4 41.5

2791 1011 587 2237

43.1 42.4 32.9 45.6

40.6–45.6 37.5–47.2 28.0–37.8 43.0–48.3

79.1 88.6 89.7 76.0

77.2–81.1 86.0–91.1 86.9–92.6 73.8–78.2

36.0 46.2 56.8 30.4

a

Difference between leisure-time walking and total walking prevalence estimates. CI, confidence interval; NPAS, National Physical Activity Survey.

between November 1999 and May 2000. When a residential telephone number was identified, the first available person aged ⱖ18 years was asked to participate. The cooperation rate (the number of complete interviews divided by households contacted with an eligible resident) was 47%.

Survey Instrument Leisure-time walking (LTW) was assessed using the 2000 BRFSS physical activity module. The pertinent query follows: “In the past month, other than your regular job, did you do any physical activities or exercises such as running, calisthenics, golf, gardening or walking for exercise?” If yes, further details about the two most common activities were elicited, including usual frequency (times per week or month), and duration (minutes and/or hours per bout). If walking was one of the top two activities reported, the participant was classified as performing LTW. Total walking (TW) was assessed by asking: “In a usual week, do you walk for at least 10 minutes at a time for recreation, exercise, to get to and from places, while at work, or for any other reason?” Respondents answering yes reported walking frequency (days/week) and duration (minutes and/or hours per day). Predominant occupational activity was also assessed: “When you are at work, which of the following best describes what you do?” Response options were “mostly sitting or standing” (henceforth “sedentary”), “mostly walking,” or “mostly heavy labor or physically demanding work” (henceforth “heavy labor”). Respondents who were “unemployed,” “home-

maker,” “student,” “retired,” or “unable to work” were categorized as not employed.

Data Analysis Walking prevalence estimates were calculated separately for the LTW and TW modules, and the prevalence difference (PD) in percentage points was used as a comparison measure. Among participants reporting any walking in either module, the total number of minutes walked per week was calculated for both LTW and TW. Significance testing was performed by the z-test for difference between the LTW and TW median minutes walked weekly. All estimates were calculated in SUDAAN, version 7.5 (Research Triangle Park NC, Research Triangle Institute, 1997) to account for the complex sampling design. Post-stratification weights for age, gender, and race/ ethnicity were applied for all analyses using the 1998 population for the 48 contiguous states. After exclusion for missing data, the final sample for analysis was 6626 (88% of the 7529 who completed interviews). The data analysis was completed in 2002.

Results Baseline Characteristics The weighted survey population was predominantly non-Hispanic white (80.5%) and had at least a high school education (90.7%) (data not shown). Slightly Am J Prev Med 2005;29(1)

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Table 2. Median minutes per week spent walking as measured by NPAS leisure-time and total walking modules Leisure-time activity module

Total walking module

Weekly minutes

Total Gender Male Female Age (years) 18–34 35–44 45–54 55–64 ⱖ65 Race/ethnicity White Black Hispanic Other Education College graduate Some college High school graduate ⬍High school Work activity Sedentary job Walking job Heavy labor job Not employed

Weekly minutes

z-test

n

Median

Q25–Q75a

n

Median

Q25–Q75a

p valueb

2900

130

59–285

5309

239

104–563

<0.0001**

905 1995

137 128

56–316 60–262

2164 3145

262 224

115–600 97–480

<0.0001** <0.0001**

711 712 582 414 481

131 127 126 128 145

60–276 53–285 57–236 56–290 52–309

1699 1337 977 608 688

253 243 264 220 207

107–711 107–599 116–585 93–447 96–419

<0.0001** <0.0001** <0.0001** <0.0001** 0.0028*

2343 294 181 82

125 147 203 203

59–261 58–349 57–438 45–408

4173 559 396 181

238 294 255 323

100–540 118–725 158–479 99–598

<0.0001** <0.0001** NS NS

963 872 874 191

122 133 135 118

55–235 56–276 59–346 39–344

1746 1574 1598 391

215 240 277 257

96–425 108–605 112–612 104–728

<0.0001** <0.0001** <0.0001** 0.0012*

1233 449 192 1026

128 130 135 134

60–262 56–296 48–402 56–285

2193 890 522 1704

203 476 595 202

87–417 203–1413 209–1471 92–417

<0.0001** <0.0001** <0.0001** <0.0001**

a

Interquartile range of 25% to 75%. bz-test for difference in medians between leisure-time and total walking. *p⬍0.01 (bolded); **p⬍0.0001 (bolded). NPAS, National Physical Activity Survey; NS, not significant; Q, quartile.

more than half the sample was female (52.4%), and slightly under half (45.7%) were aged ⱖ45 years. The distributions of gender, age, race/ethnicity, and education level did not differ significantly from that of the 2000 BRFSS (data not shown). Among the two thirds who were employed, 41% reported doing sedentary work, 15% “mostly walking,” and 10% “heavy labor.” The remaining one third of respondents not currently employed were homemakers (6.9%), students (4.7%), retired (16.1%), unemployed (3.0%), or unable to work (3.0%).

Performing Any Walking: Leisure-Time Walking Versus Total Walking Walking prevalence estimated from the TW module was nearly twice that estimated using the LTW module (80.5% vs 42.9%; PD⫽37.6) for the overall sample (Table 1). The magnitude of the PD between LTW and TW varied among sociodemographic subgroups. The greatest disparity between estimates occurred for men (PD⫽46.7), respondents aged 18 to 34 years (PD⫽50.4), and high-activity workers (PD⫽46.2 for “mostly walking” and PD⫽56.8 for “heavy labor”). The smallest disparities between estimates occurred for women (PD⫽29.1) and respondents aged ⱖ65 years (PD⫽21.5). 48

Time Spent Walking The median minutes spent walking per week estimated by the TW module was 109 minutes greater than that estimated from the LTW module (Table 2). The degree of disparity between the LTW and TW in estimated weekly walking times varied by demographic subgroup. The smallest differences in estimated minutes of walking per week occurred among those aged ⱖ65 years (62 minutes), among those not currently employed (68 minutes), and among Hispanics (52 minutes). The greatest gap between the LTW and TW weekly walking estimates occurred among workers who “mostly walk” (346 minutes) and do “heavy labor” (460 minutes).

Discussion This nationally representative study describes walking prevalence estimates obtained using a leisure-time survey module and a module inclusive of both leisure and nonleisure walking. As expected, the broader measure produced both a substantially greater walking prevalence (80.5% vs 42.9%) and a greater median weekly walking time (239 minutes vs 130 minutes). These results were consistent with smaller studies that have

American Journal of Preventive Medicine, Volume 29, Number 1

compared leisure and nonleisure walking,19,20 and suggest that baseline daily walking among U.S. adults may be greater than previously estimated. The accurate assessment of total walking is important to public health physical activity campaigns, as messages designed to encourage walking might be more effectively targeted and accurately evaluated when all baseline walking in the population is taken into account. Although the TW module set a low threshold for capturing any walking activity (10 continuous minutes per week), the vast majority reported quantities of weekly walking with the potential to provide some health benefits, which have been described with as little as 1 hour per week of brisk walking.13 It was not possible to determine how much TW was at the “brisk” intensity suggested by current physical activity guidelines.27,28 Nonetheless, even low-intensity walking may contribute cumulative health benefits. Pedometer studies have demonstrated positive associations between higher amounts of daily walking and positive cardiovascular and metabolic health associations independent of the context and intensity of walking reported.29 Thus, increased volumes of any walking may provide health benefits as compared with little or no walking at all. A key difference between the two modules was the inclusion of occupational walking in the TW module. Inclusion of the latter activities showed nearly double the time reported in walking behaviors, and reflects the importance of these activities in the total time spent in physical activity, particularly among high activity workers. While occupational activities are not specifically addressed in current guidelines,27,28 recent studies have reported that moderate occupational activity such as walking independently reduces the risk of diabetes and cardiovascular disease.30,31 The strengths of this study include a large nationally representative sample and the unique opportunity to evaluate two separate activity modules within the same sample. Limitations include the absence of an objective measure of walking, which could result in under- or over-reporting of walking. Second, the low response rate and exclusion of non–telephone owners limit the generalizability of these findings. Third, because the context of walking reported in the total walking module was not ascertained, the relative contributions of walking in different contexts could not be evaluated. Finally, although the LTW module has been used to describe patterns of leisure-time walking,15,16 it was not designed specifically to assess walking. This, in addition to the different timeframes of each module (1 month vs 1 week), may have differentially affected the reporting and recall of walking.32 In conclusion, this study describes disparities in walking estimates based solely on a leisure-time activity measure and a measure covering both leisure and nonleisure walking. Further characterization of nonleisure walking by context and intensity is needed to

What This Study Adds . . . Although walking is a fundamental component of many nonleisure activities (such as transportation, occupation, and household work), epidemiologic studies of walking have primarily assessed only leisure-time walking. This nationally representative study suggests that U.S. adults do a substantial amount of walking that is not being captured by traditional leisure-time physical activity surveys. Accurate estimates for all walking domains are needed to appropriately target physical activity promotion messages and interventions and to measure their effectiveness.

determine its health benefits, and to provide a solid basis for targeting and motivating sedentary adults to become more active by walking. No financial conflict of interest was reported by the authors of this paper.

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