Walking the Dog: Is Pet Ownership Associated With Physical Activity in California?

Journal of Physical Activity and Health, 2008, 5, 216-228 2008 Human Kinetics, Inc. Walking the Dog: Is Pet Ownership Associated With Physical Activity in California? K. Robin Yabroff, Richard P. Troiano, and David Berrigan Background: Several studies have reported positive associations between pet ownership and a variety of health outcomes. In this study, we explored associations between pet ownership and physical activity in a large, ethnically diverse population-based sample in California. Method: Data from the California Health Interview Survey (CHIS) were used to assess the associations between pet ownership (ie, dog, dog and cat, cat, and non pet owners) and transportation and leisure walking in a sample of 41,514 adults. Logistic regression was used to assess associations between pet ownership and type of walking, and linear regression was used to assess associations between pet ownership and total minutes walking per week. Results: Dog owners were slightly less likely to walk for transportation than were non pet owners (OR = 0.91; 95% CI: 0.85 to 0.99) but more likely to walk for leisure than non pet owners (OR = 1.6; 95% CI: 1.5 to 1.8) in multivariate analyses. Overall, dog owners walked 18.9 (95% CI: 11.4 to 26.4) minutes more per week than non pet owners. Walking behaviors of cat owners were similar to non pet owners. Conclusion: Our findings support the moderate association between dog ownership and higher levels of physical activity. Keywords: walking/statistics and numerical data, dogs, cats Multiple studies have reported positive associations between pet ownership and a variety of human health outcomes, 1-9 including greater survival among coronary patients, 5 lower risk of myocardial infarction, 4 lower prevalence of cardiovascular risk factors, 6,7 and less health care resource use. 8 Proposed mechanisms for positive health effects of pet ownership include direct social and emotional support between humans and pets, increased physical activity among pet owners, increased social interaction among humans with pets, and the development of community social capital. 1-3,9 Although some studies have reported little association between pet ownership and health outcomes, 3,10 inconsistencies in findings might be the result in part of small convenience samples, and differences in types of pets and geographic regions evaluated, population characteristics, sample selection, measures of health, and analytic methods. 1-3 Yabroff and Berrigan are with the Applied Research Program, and Troiano the Risk Factor Monitoring and Methods Branch, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, MD 20892. 216

Pet Ownership and Walking 217 Previous studies have examined the association between dog ownership and physical activity. 1,11-18 Because dog walking is a traditional element of pet ownership and a routine activity, it might contribute to increased physical activity. Although dog owners are generally reported to be more physically active than non dog owners, findings related to the magnitude of any effect have varied widely. 1,11-15,17,18 Most of these studies have been conducted in a single country (Australia), in convenience samples, or did not differentiate between walking for transportation and leisure. In addition, some studies only assessed dog walking in dog owners, 15,16 and as a result could not compare physical activity in dog owners to similar individuals without dogs. Because of international variation in levels of obesity, 19 physical activity, 20 and pet ownership, confirming these findings in the United States will be important. In this study, we examined the associations between pet ownership and leisure and transportation walking in a large, ethnically diverse population-based sample in California, the most populous state in the United States. We evaluated ownership of cats and dogs, the 2 most common pets in the United States, 21 and walking, the most common form of physical activity. 22 We hypothesized that dog ownership would be associated with higher levels of walking compared with non pet owners. Because we hypothesized that walking among cat owners would be similar to non pet owners, we also evaluated cat owners to control for other correlates of pet ownership. Study Population Methods The study population was selected from the 2003 California Health Interview Survey (CHIS), a random-digit-dial telephone multistage survey designed to yield stateand local-level estimates of health and health behaviors in California. The CHIS is a large survey with more than 55,000 participants. The survey was administered in 7 languages (English, Spanish, Mandarin, Cantonese, Vietnamese, Korean, and Khmer) throughout the year. Overall response rates of approximately 33% are similar to response rates for other contemporaneous population-based telephone surveys in the United States. 23 More information about the survey, including procedures, survey questions, and development of sample weights to ensure the sample is representative of California, is available online (http://www.chis.ucla.edu). We included adult respondents age 18 and older with complete responses to questions about walking, pet ownership, and the demographic and health variables described below (N = 41,514). Measures We used 3 outcome variables related to walking, including transportation walking (yes, no), leisure walking (yes, no), and total minutes walking in bouts of 10 minutes or more per week, for both leisure and transportation. Transportation walking (yes, no) was based on responses to the question, During the past 7 days, did you walk to get some place that took you at least 10 minutes? The question was prefaced by a prompt, The next questions are about walking for transportation. I will ask you separately about walking for other reasons like relaxation or exercise. Leisure

218 Yabroff, Troiano, and Barrigan walking (yes, no) was based on responses to the following, Sometimes you may walk for fun, relaxation, exercise, or to walk the dog. During the past 7 days, did you walk for at least 10 minutes for any of these reasons? Measurement of walking in bouts of 10 minutes or more is consistent with public health recommendations for physical activity, 22,24 and these measures have been used in other surveys, including the National Health Interview Survey (www.cdc.gov/nchs/nhis/htl), one of the primary sources of information about health behavior in the United States. These questions about transportation and leisure walking were each followed by a question about the number of times per week the respondent walked at least 10 minutes ( In the past 7 days, how many times did you do that? ) and a question about the duration of the walks ( On average, how long did those walks take? ). Total minutes of transportation walking per week and leisure walking per week were the product of responses to questions about the number of times in the past week that the respondent walked in bouts of at least 10 minutes for transportation or leisure and the average duration of the walks. A summary measure for combined transportation and leisure walking in bouts of 10 minutes or more was calculated by adding total minutes of transportation and total minutes of leisure walking per week. Pet ownership, the main covariate of interest, was defined by responses to the questions, Do you have any dogs that you allow inside your home? and Do you have any cats that you allow inside your home? These questions were included in the CHIS as part of a series of questions about asthma. Individuals were classified with a single variable with 4 categories: no pet, dog owner, cat owner, or dog and cat owner. The survey also included questions related to potential confounders of associations between pet ownership and leisure and transportation walking. Sociodemographic characteristics included age (18 29, 30 39, 40 49, 50 59, 60 69, 70+), gender (male, female), race/ethnicity (Latino, Asian/Pacific Islander, African American, White, other), marital status (married or living as married, other), educational attainment (<12th grade, 12th grade, >12th grade), employment (working at a job, has a job but not at work, looking for work, not working), and income as a percentage of the federal poverty level (0% to 99%, 100% to 199%, 200% to 299%, 300+%). The poverty level is an index that accounts for family size and is standardized for inflation and other factors (http://www.census.gov/hhes/www/ poverty.html). General health characteristics were self-rated health (excellent, very good, good, fair, poor) and body mass index (<25, 25 to 29, 30+). Housing characteristics were defined as house, duplex, building with 3 or more units, and mobile home. Analyses Descriptive statistics were calculated for the sample by pet-ownership status. Leisure walking, transportation walking, and total minutes walking per week were also compared by pet-ownership status. Categorical variables were compared with chi-square statistics, and means for continuous variables were compared using linear regression. Bivariate and multivariate logistic regression analyses were used to evaluate the associations between pet ownership and leisure walking and transportation walking. Bivariate and multivariate linear regression analyses were used to evaluate the associations between pet ownership and total minutes of leisure and

Pet Ownership and Walking 219 transportation walking per week. The relationship between potential covariates and walking was examined before including the covariates in multivariate analyses. All tests of statistical significance were two-sided. We used SUDAAN to incorporate the complex CHIS survey design 25 following recommendations discussed in Korn and Graubard 26 and the CHIS Methodological Series. 23 Results Most of the sample was younger than 50, married or living with a partner, had at least a high school education, and reported working at a job (Table 1). About half were female and non-white. Most reported owning neither a cat nor dogs (60.8%); whereas 17.7% reported owning a dog; 13.0%, a cat; and 8.5% both a dog and a cat. Overall, 43.7% of the sample reported transportation walking, with a mean of 51.1 (95% CI: 48.7 to 53.4) minutes per week (in bouts of 10 minutes or more, Table 2). Fewer dog owners and dog and cat owners reported transportation walking than non pet owners (P <.01). Dog owners and dog and cat owners also reported shorter duration of transportation walking (P <.01). A slightly larger proportion of the sample reported leisure walking (55.9%) for an average of 68.9 (95% CI: 67.4 to 70.4) minutes per week. More dog owners and dog and cat owners reported leisure walking than individuals without these pets (P <.01). The average duration of leisure walking was also greater for dog owners and dog and cat owners than for non pet owners (P <.01). Walking in cat owners was more similar to walking in non pet owners than to dog owners or dog and cat owners. Controlling for the effects of sociodemographic characteristics, general health characteristics, and housing characteristics, dog owners were slightly less likely to walk for transportation than were non pet owners (OR = 0.91; 95% CI: 0.85 to 0.99; Table 3). However, dog owners and dog and cat owners were more likely to walk for leisure than non pet owners (OR = 1.64; 95% CI: 1.52 to 1.77 and OR = 1.29; 95% CI: 1.16 to 1.38, respectively) in adjusted analyses (Table 3). Cat owners were slightly less likely to walk for leisure than non pet owners in adjusted analyses (OR = 0.91; 95% CI: 0.84 to 0.99). When total minutes of walking per week for transportation and leisure was assessed in multivariate linear regression analyses, dog owners walked 18.9 (95% CI: 11.4 to 26.4) minutes more per week than non pet owners, and dog and cat owners walked 14.8 (95% CI: 5.1 to 24.4) minutes more per week than non pet owners (Table 4). Total minutes of walking per week were similar for cat owners and non pet owners in multivariate analyses. Discussion In this study, we used data from a large, ethnically diverse, population-based sample in California to evaluate associations between pet ownership and transportation and leisure walking. We found that overall, dog owners walked more than non pet owners, and walking in cat owners was similar to walking in non pet owners. These findings were consistent with our hypothesis and suggest that physical activity might play a role in the positive health benefits of pet ownership in dog owners. Previous

Table 1 Sample Characteristics by Pet-Ownership Status, Weighted a % (SE) n Total (N = 41,514) No pet (n = 25,240) Dog owner (n = 7348) Cat owner (n = 5397) Dog and cat owner (n = 3529) Overall 100.0 60.8 (0.3) 17.7 (0.2) 13.0 (0.2) 8.5 (0.2) Sociodemographic characteristics Gender male 17,241 49.0 (0.0) 62.3 (0.5) 17.6 (0.4) 12.3 (0.3) 7.8 (0.2) female 24,273 51.0 (0.0) 59.3 (0.4) 17.8 (0.3) 13.7 (0.3) 9.2 (0.2) Age 18 29 y 6225 23.2 (0.0) 66.2 (0.8) 14.8 (0.6) 12.2 (0.5) 6.8 (0.4) 30 39 y 7593 21.4 (0.0) 64.7 (0.8) 16.1 (0.6) 11.5 (0.4) 7.7 (0.4) 40 49 y 8805 20.8 (0.0) 54.3 (0.6) 20.3 (0.5) 13.9 (0.4) 11.5 (0.4) 50 59 y 7698 15.1 (0.1) 51.2 (0.7) 22.1 (0.6) 16.1 (0.5) 10.7 (0.4) 60 69 y 5281 9.3 (0.1) 59.3 (0.9) 17.6 (0.7) 14.5 (0.7) 8.6 (0.5) 70+ y 5912 10.1 (0.1) 69.0 (0.7) 15.7 (0.7) 10.5 (0.5) 4.8 (0.3) Race/Ethnicity Latino 7080 26.1 (0.1) 80.3 (0.6) 11.5 (0.4) 5.7 (0.4) 2.4 (0.2) Asian/Pacific Islander 4006 12.3 (0.0) 79.7 (1.0) 12.5 (0.8) 5.8 (0.4) 2.1 (0.3) African American 2652 6.3 (0.0) 78.6 (0.9) 13.3 (0.8) 6.2 (0.6) 1.9 (0.4) White 26,115 51.4 (0.1) 44.5 (0.4) 22.6 (0.3) 19.1 (0.3) 13.9 (0.3) other 1661 3.9 (0.1) 56.6 (1.8) 18.1 (1.2) 15.8 (1.3) 9.6 (0.9) 220

Marital status married or living with partner 23,699 62.1 (0.3) 58.7 (0.4) 19.2 (0.3) 12.9 (0.3) 9.1 (0.2) other 17,815 37.9 (0.3) 64.1 (0.5) 15.2 (0.4) 13.2 (0.3) 7.5 (0.3) Education <12th grade 5177 20.1 (0.1) 79.8 (0.7) 10.3 (0.5) 6.3 (0.4) 3.7 (0.3) 12th grade 9927 23.7 (0.2) 58.4 (0.6) 18.5 (0.5) 13.2 (0.4) 9.9 (0.4) >12th grade 26,410 56.1 (0.2) 55.0 (0.4) 20.0 (0.3) 15.4 (0.3) 9.7 (0.2) % of FPL 0 99 4742 15.0 (0.3) 80.7 (0.6) 8.4 (0.6) 6.9 (0.5) 4.0 (0.3) 100 199 7038 18.8 (0.3) 72.6 (0.8) 12.7 (0.5) 8.8 (0.4) 5.9 (0.4) 200 299 5981 14.0 (0.2) 62.2 (0.8) 15.8 (0.8) 13.0 (0.6) 9.0 (0.4) 300+ 23,753 52.3 (0.3) 50.4 (0.5) 22.6 (0.4) 16.3 (0.3) 10.6 (0.2) Employment status in past week working at a job 23,536 59.9 (0.3) 58.2 (0.5) 18.4 (0.3) 13.9 (0.3) 9.4 (0.2) has job, not at work 1286 2.7 (0.1) 52.5 (1.9) 21.4 (1.3) 14.8 (1.3) 11.2 (1.1) looking for work 1974 6.1 (0.2) 67.8 (1.4) 14.4 (1.0) 11.7 (0.9) 6.1 (0.7) not working 14,718 31.2 (0.2) 65.0 (0.5) 16.6 (0.4) 11.4 (0.3) 7.0 (0.3) General health Self-rated health excellent 9187 21.7 (0.3) 54.5 (0.7) 20.6 (0.6) 15.0 (0.5) 9.9 (0.4) very good 13,161 29.9 (0.3) 54.9 (0.6) 20.1 (0.5) 14.9 (0.4) 10.1 (0.3) good 11,383 28.4 (0.3) 64.5 (0.6) 15.9 (0.4) 11.9 (0.4) 7.7 (0.3) fair 5819 15.6 (0.2) 72.8 (0.8) 12.5 (0.6) 9.4 (0.4) 5.3 (0.4) poor 1964 4.4 (0.1) 65.3 (1.5) 16.3 (1.2) 10.6 (1.0) 7.8 (0.9) (continued) 221

Table 1 (continued) n Total (N = 41,514) No pet (n = 25,240) Dog owner (n = 7348) Cat owner (n = 5397) Dog and cat owner (n = 3529) Body mass index <25 kg/m 2 18,828 44.5 (0.4) 60.8 (0.5) 17.1 (0.3) 13.5 (0.3) 8.6 (0.2) 25 to <30 kg/m 2 14,223 35.2 (0.3) 60.3 (0.5) 18.7 (0.4) 12.8 (0.4) 8.3 (0.3) 30+ kg/m 2 8463 20.3 (0.3) 61.6 (0.7) 17.2 (0.5) 12.4 (0.4) 8.8 (0.3) Housing Housing type house 28,285 65.9 (0.3) 53.3 (0.4) 22.3 (0.3) 13.3 (0.3) 11.1 (0.2) duplex 2065 5.7 (0.2) 66.6 (1.5) 14.6 (1.1) 13.6 (1.1) 5.3 (0.6) building with 3+ units 9285 24.7 (0.3) 79.6 (0.5) 6.2 (0.3) 12.1 (0.4) 2.1 (0.2) mobile home 1879 3.6 (0.1) 59.3 (1.7) 16.6 (1.2) 13.5 (1.2) 10.5 (1.0) Abbreviation: FPL, federal poverty level. a Use of sample weights yields estimates representative of the state of California. 222

Table 2 Transportation and Leisure Walking by Pet-Ownership Status Pet ownership Total No pet Dog owner Cat owner Dog and cat owner P value b Transportation walking yes, weighted a % (SE) 43.7 (0.3) 46.2 (0.4) 38.6 (0.7) 41.8 (0.8) 39.5 (1.0) <.01 no, weighted a % (SE) 56.3 (0.3) 53.8 (0.4) 61.4 (0.7) 58.2 (0.8) 60.5 (1.0) mean min walking per week (SE) 51.1 (1.2) 55.1 (1.3) 43.2 (2.4) 46.5 (4.6) 46.3 (3.7) <.01 Leisure walking yes, weighted a % (SE) 55.9 (0.4) 52.8 (0.6) 66.4 (0.7) 53.2 (0.9) 60.5 (1.0) <.01 no, weighted a % (SE) 44.1 (0.4) 47.2 (0.6) 33.6 (0.7) 46.8 (0.9) 39.5 (1.0) mean min walking per week (SE) 68.9 (0.8) 64.6 (1.1) 86.1 (1.6) 61.5 (1.8) 75.7 (2.3) <.01 Transportation and leisure walking either, weighted a % (SE) 73.0 (0.3) 72.4 (0.4) 76.7 (0.6) 70.4 (0.6) 73.3 (0.9) <.01 neither, weighted a % (SE) 27.0 (0.3) 27.6 (0.4) 23.3 (0.6) 29.6 (0.6) 26.7 (0.9) mean min walking per week (SE) 120.0 (1.6) 119.7 (1.8) 129.3 (3.0) 107.9 (5.1) 122.0 (4.4) <.01 a Use of sample weights yields estimates representative of the state of California. b Categorical variables were compared with chi-square statistics, and means for continuous variables were compared using linear regression. 223

Table 3 Association Between Pet-Ownership Status and Transportation and Leisure Walking Pet ownership and transportation walking Pet ownership and leisure walking Adjusted for sociodemographic a characteristics Fully adjusted b Unadjusted Adjusted for sociodemographic a characteristics Fully adjusted b Unadjusted OR 95% CI OR 95% CI OR 95% CI OR 95% CI OR 95% CI OR 95% CI No pet 1.0 1.0 1.0 1.0 1.0 1.0 Dog owner 0.7 (0.7 0.8) 0.8 (0.8 0.9) 0.91 (0.85 0.99) 1.8 (1.6 1.9) 1.6 (1.5 1.7) 1.6 (1.5 1.8) Cat owner 0.8 (0.8 0.9) 1.0 (0.9 1.0) 1.0 (0.9 1.1) 1.0 (0.9 1.1) 0.9 (0.8 1.0) 0.9 (0.8 1.0) Dog and cat owner 0.8 (0.7 0.8) 0.9 (0.8 1.0) 1.0 (0.9 1.1) 1.4 (1.3 1.5) 1.2 (1.1 1.3) 1.3 (1.2 1.4) a Adjusted for gender, age in deciles, race/ethnicity, educational attainment, income as a percentage of federal poverty level, and marital status. Associations between all covariates and walking were all statistically significant at P <.05. b Adjusted for gender, age in deciles, race/ethnicity, educational attainment, income as a percentage of federal poverty level, marital status, self-rated health status, body mass index, housing type, and employment status. Associations between all covariates and walking were all statistically significant at P <.05. 224

Pet Ownership and Walking 225 Table 4 Association Between Pet-Ownership Status and Total Minutes of Walking per Week Unadjusted Adjusted for sociodemographic characteristics a Fully adjusted b coefficient 95% CI coefficient 95% CI coefficient 95% CI No pet 0.0 0.0 0.0 Dog owner 9.6 (2.8 16.4) 16.1 (8.6 23.6) 18.9 (11.4 26.4) Cat owner 11.7 ( 21.9 to 1.5) 5.1 ( 17.0 to 6.8) 3.9 ( 15.5 to 7.8) Dog and cat owner 2.3 ( 7.0 to 11.6) 10.5 (0.7 20.3) 14.8 (5.1 24.4) a Adjusted for gender, age in deciles, race/ethnicity, educational attainment, income as a percentage of federal poverty level, and marital status. b Adjusted for gender, age in deciles, race/ethnicity, educational attainment, income as a percentage of federal poverty level, marital status, self-rated health status, body mass index, housing type, and employment status. Associations between all covariates and walking were all statistically significant at P <.05. studies of pet ownership and health have included some physiologic measures of health 1-3 ; addition of measures of dog walking will be important in future research, especially given the importance of physical activity in many health outcomes. 22 A number of public health guidelines recommend accumulating at least 30 minutes of moderate activity on 5 or more days per week, for a minimum of 150 minutes per week, 24,27 in bouts lasting 10 minutes or more. 24 Only a small proportion of Americans actually meet these recommended levels of physical activity. 28 Approximately one-fourth of the adult population is sedentary, 29 and among adults who report any walking, the median duration is approximately 86 minutes per week. 30 Thus, in relation to current levels of physical activity, our findings that dog ownership is associated with an average of 19 more minutes spent walking per week compared with non dog or cat owners might be significant. Studies have suggested that even modest increases in physical activity can have health benefits, 31 particularly in combination with other lifestyle changes. 32 Because a substantial portion of the US population own dogs, 21 dog ownership could be a useful covariate in the studies of the causes and consequences of physical activity. Most of the previous studies of dog ownership and physical activity have been conducted in Australia, 11-14 and our findings are generally consistent with those studies. 12,13 Our study is one of the only population-based studies in the United States to have a large enough sample to explore associations between pet ownership and physical activity for different types of pets separately compared with non pet owners. Because physical activity is a possible mechanism through which pet owners experience health benefits, evaluating walking behaviors in owners of pets other than dogs can control for other correlates of pet ownership. In a study conducted in a Midwestern metropolitan area in the United States, Suminski and colleagues assessed dog walking by types of neighborhood features, but did not report the amount of walking or compare overall walking for dog owners and nonowners. 16 Ham and Epping reported daily frequency and duration of dog walking

226 Yabroff, Troiano, and Barrigan in the United States but did not describe total walking or compare their findings to walking behaviors in non dog owners. 15 Another smaller study conducted in western Canada also reported that dog owners participated in more mild to moderate physical activity than non dog owners 17 but did not report findings for other types of pets. Our findings suggest that mechanisms for potential health benefits of pet ownership might differ for cats and dogs, with little evidence of a physical activity benefit of cat ownership. Future studies should consider evaluating the relation between different types of pets (including dogs) and physical activity and health outcomes separately. We found that dog owners were more likely to walk for leisure but less likely to walk for transportation. It is likely that dog walking among those who walk their dogs is a routine activity, consistent with the positive association between dog ownership and leisure walking. In addition, it is possible that because walking the dog was included as an example of leisure walking, dog owners might have been more likely to classify their multipurpose trips as leisure rather than transportation. The CHIS is one of the first large surveys in the United States to include questions about both transportation and leisure walking. Others have reported that including only leisure walking in surveys underestimates total walking, 33 potentially resulting in misclassification. In addition, as demonstrated in this study, factors might be differentially associated with these 2 types of walking. Because walking is the most common form of physical activity in the United States 22 and leisure and transportation walking have different demographic and environmental correlates, 11 evaluation of the correlates of both transportation and leisure walking will be important in future studies. Despite the strengths of a large, multiethnic, population-based sample, there are several limitations associated with our study, including a relatively low response rate in the CHIS, use of data from only a single state rather than the entire United States, and use of self-report data to assess walking behaviors. Although California is the most ethnically diverse state in the United States, and is geographically diverse as well, there might be climate and environmental differences that might affect generalizability. In addition, the CHIS was not designed specifically to address questions about pet ownership and physical activity. The wording of the question we used to identify pet ownership was related to cats and dogs allowed in the home and did not specify them as pets. Misclassification of individuals who allow dogs or cats in the house as pet owners would likely underestimate the strength of any associations we observed, however. We did not have any information on the relationship between the owner and pet or pet characteristics, such as pet health, age, breed, or size. Pet size has been reported elsewhere to be associated with walking behavior. 14 In addition, we could not distinguish dog-walking from walking for other purposes. Overreporting of physical activity compared with its direct measurement has been described elsewhere, 34 although we have no reason to believe that overreporting would differentially vary for cat and dog owners and non pet owners. Finally, the CHIS is a cross-sectional survey; we cannot infer causality in the association between pet ownership, walking, and health. In summary, our findings support moderate associations between dog ownership and higher levels of walking. Inclusion of physical activity measures, both leisure and transportation walking, and evaluation of type of pet separately might inform future research related to pet ownership and health.

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