Lail et al. BMC Public Health 2011, 11:148 http://www.biomedcentral.com/1471-2458/11/148 Several quantitative studies have found that dog-owners tend to be more physically active than non-owners [11,19]; all of these cross-sectional studies, however, were conducted in geographical areas with mild or moderate climates, including one Canadian study [19] undertaken in a coastal city with a temperate climate. Focus group research, meanwhile, suggests that dog-owners view their dogs as a source of companionship and motivation for get- ting outdoors and walking [20,21] - regardless of weather conditions [21]. As one participant put it, “But if you’ve got a dog, you’ve got to come out in all weathers” [21], p.443], while another said, “If it’s absolutely foul weather sometimes you think, oh dear, I’ve got to go out, but once you’re out there, providing you’re dressed appropriately, it’s just fabulous, so yes, so I walk every day” [21], p.444]. The available evidence thus suggests a potential role for dog-ownership in overcoming or mitigating the reduction in physical activity often observed during winter months, but this possibility has yet to be examined quantitatively. We investigated the extent to which dog-ownership influ- ences seasonal patterns in neighbourhood-based walking among adults living in highly-variable climate. Method Sample, Setting and Data Collection This paper presents longitudinal findings among respon- dents nested within a larger observational study. A ran- dom cross-section of adults (n = 2223) residing in Calgary, Canada participated in telephone-interviews in winter 2007/08 (January to April) as part of the EcoEU- FORIA (Economic Evaluation of Using Urban to Increase Activity) project. One adult per household was invited to participate in the telephone-interview. To be eligible to participate, respondents had to reside in the Calgary metropolitan area, be 18 years or older, and be proficient in English. Details regarding the telephone survey are fully described elsewhere [7]. The Conjoint Health Research Ethics Board at the University of Calgary approved this study. The Calgary metropolitan area is 745 km2, includes 1071515 residents and 122325 dog-owning households [22] and offers a relatively high standard of living [23]. Located east of the Rocky Mountains, Calgary is elevated over one-kilometer above sea level, and has a continental climate. Calgary winters are characterized by subzero temperatures, snow fall, and periodic daytime thaws fol- lowed by overnight freezing, resulting in icy conditions. Summers in Calgary, meanwhile, are characterized by warm temperatures with some precipitation and occa- sional heat waves. The amount of daylight also varies considerably from summer to winter. At winter solstice (21 December), sunset occurs 7.9 hours after sunrise, whereas at summer solstice (21 June), sunset occurs 16.56 hours after sunrise [24]. During the winter data Page 2 of 7 collection (January to April 2008), the mean temperature ranged from -8.5 to 1.5 degrees Celsius, with total snow- fall ranging from 16.8 to 65.8 cm per month, respectively [25]. During the summer data collection (August, 2009), the mean temperature was 15.9 degrees Celsius, with a total rainfall of 62.2 mm [25]. Of those who completed the telephone-interview, 1823 respondents agreed to complete a postal questionnaire, which was sent out within one week of completing the telephone interview. Postal questionnaires measured, among other variables, demographic characteristics (income, education, age, sex, housing tenure and housing type), health behaviours, and dog-ownership [7]. Overall 1049 respondents completed and returned the postal questionnaire (by April 2009). Of those, 798 agreed to participate in a second postal questionnaire sent in sum- mer (August, 2009). The second postal questionnaire included an expanded set of dog-ownership questions, as well as repeating the physical activity items from the tele- phone survey. A total of 428 respondents completed both the winter and summer questionnaires (Figure 1). Measures Demographic characteristics The winter telephone-interview and questionnaire cap- tured baseline demographic characteristics including age, sex, annual household income (<$60000, 60000-119999, or ≥120000), highest education achieved (≤high school, technical college, undergraduate university, or postgradu- ate university), marital status (single or married), ethni- city (white or non-white) and housing type (detached/ semi-detached or other housing). Neighbourhood-specific walking The winter telephone-interview and the summer question- naire included items from the Neighbourhood Physical Activity Questionnaire [26] capturing transportation and recreational walking undertaken inside the neighbourhood during a usual week (everywhere within a 15-minute walk from home). Specifically, respondents were asked: “In a usual week how many times do you walk as a means of transportation such as going to and from work, walking to the store or walking to the bus stop or LRT in your neigh- bourhood or local area?” Respondents were also asked: “In a usual week how many times do you walk for recreation, health or fitness (including walking your dog) in or around your neighbourhood or local area?” Respondents reporting participation also reported the total time spent walking for transportation or recreation in their neighbourhood. Neighbourhood-specific walking items capturing fre- quency and duration have been shown to have acceptable reliability [26,27]. Dog-ownership In the winter and summer questionnaires respondents reported the number of dogs their household owned.