The association between dog ownership or dog walking and fitness or weight status in childhood.

BACKGROUND: Health benefits of dog walking are established in adults: dog owners are on average more physically active, and those walking their dogs regularly have lower weight status than those who do not. However, there has been little research on children.
OBJECTIVES: This study aimed to examine the association between dog ownership or dog walking and childhood fitness or weight status.
METHODS: A survey of pet ownership and involvement in dog walking was combined with fitness and weight status measurements of 1021 9 to 10-year-old children in the Liverpool SportsLinx study.
RESULTS: We found little evidence to support that children who live with, or walk with, dogs are any fitter or less likely to be obese than those who do not.
CONCLUSIONS: This is an important finding, as it suggests that the activity that children currently do with dogs is not sufficient enough to impact weight status or fitness.

Introduction

Dog‐owning adults are on average more physically active than non‐owners 1, and there is some evidence that owners who walk their dogs are less likely to be obese than both owners who do not walk with their dogs and non‐dog owners 2. A few studies show that children who own dogs are marginally more physically active 3, 4, 5, although others do not 6, but there has been little research into other health outcomes, especially regarding actual involvement in dog walking, as opposed to simply dog ownership 4, 6, 7, 8. This study examined the association of dog ownership and involvement in dog walking with childhood obesity and overweight. It also examined, for the first time, the association between dog ownership and involvement in dog walking with fitness measures.

Methods

Data collection has been described previously 9, 10, 11, 12, 13, 14. Briefly, over 10 weekdays in October–November 2010, 1021 9 to 10‐year‐old children, from 31 schools, were sampled during attendance at SportsLinx Fitness Fun Days in Wavertree, Liverpool, UK. The children completed the Child Lifestyle and Pets Questionnaire as part of their rotation of activities. Participation in SportsLinx is subsequent to granted informed parental consent and participant assent and after the completion of medical screening forms. Ethical approval for the addition of the Child Lifestyle and Pets Questionnaire to a sample of the 2010–2011 SportsLinx data collection was obtained from the North West 3 Research Ethics Committee – Liverpool East.

The children were asked about the pets they currently owned and how often they walked with any dog (theirs or someone else's) and walked with their own dog. Frequency was recorded as never, once a week or less, several times a week or once a day or more. To ensure sufficient numbers for analyses, this was further collapsed into a two‐level variable of ‘once a week or less’ vs. ‘several times a week or more’. Parental consent forms collected information such as gender, age and home postcode (used to assign Index of Multiple Deprivation 2007). Developmental age was estimated via years to peak height velocity by using the equation developed by Mirwald 15. Outcomes measured during EUROFIT fitness testing included 20‐m multi‐stage shuttle runs test, 10 × 5 agility, sit and reach, standing broad jump and grip strength 16. Height and weight (Seca, Bodycare, Birmingham, UK), both measured by instructors, were used to calculate BMI. Age‐ and sex‐specific cut‐off points (International Obesity Task Force; 17) were used to classify the participants in binary terms as being ‘overweight or obese’ or ‘obese’.

Predictive variables tested were lives with a dog, frequency of walks with any dog and frequency of walks with own dog. Univariable analysis was conducted by using t‐test or Kruskal–Wallis tests, followed by adjustment for confounders by using regression modelling in mlwin. For continuous measures, non‐normally distributed data were transformed (log10). Multivariable two‐level models were developed initially by using a residual iterative generalized least‐square algorithm, and then for binary outcomes, a second‐order penalized quasi‐likelihood 18. The variables ‘school’ and ‘child’ were set as levels 2 and 1 respectively, to account for non‐independence of the data (children clustered in schools). All models were adjusted for gender, developmental age and Index of Multiple Deprivation 2007. Analyses were also conducted stratified by gender in case there was evidence of effects in boys but not girls (or vice versa), but we did not find anything of interest (data not shown). Fitness outcome models were also adjusted for BMI standard deviation score, and weight status models are presented both with and without additional adjustment for positive and negative food score intake 19. Sample size calculations estimated that to detect a 50% reduction in risk of overweight (comparable to published interventions; 20) with expected 25% dog ownership 21 or 65% dog‐owning children walking with their dog several times a week or more 14, it would require 600 and 100 participants respectively (95% confidence level, 80% power).

Results

Table 1 shows evidence that dog ownership, but not dog walking, may be associated with lower flexibility (P = 0.01) and explosive leg strength (standing broad jump: P = 0.003). More frequent dog walking of own or any dog was weakly associated with greater grip strength (P = 0.03–0.05). There was no evidence of an association between dog ownership or dog walking and obesity or overweight (Table 2). In model 2 of Table 2, we further adjusted for a measure of nutrition, using ‘positive’ (healthy) and ‘negative’ food intake by food types indicated 19. Interestingly, this reversed the direction of effect for dog walking variables to protective but remained insignificant.

Table 1

Multi‐level multivariable regression models of association between living with a dog and walking a dog, with childhood fitness

Outcome					Crude*			Adjusted†
Variable	n	Median		Kruskal Wallis test	Coef	SE coef	P	Coef	SE coef	P
20‐m SRT		(Runs)
Lives with a dog
No	566	30.00		0.38
Yes	333	29.00			−0.01	0.02	0.44	−0.01	0.02	0.75
Frequency walks with any dog
Once a week or less	575	29.00		0.91
Several times a week or more	238	32.00			−0.00	0.02	0.82	0.01	0.02	0.44
Frequency walks with own dog
Once a week or less	101	28.00		0.42
Several times a week or more	186	29.50			0.03	0.03	0.35	0.04	0.03	0.15
10 × 5 agility		(s)
Lives with a dog
No	576	22.54		0.40
Yes	333	22.59			0.00	0.00	0.50	0.00	0.00	0.50
Frequency walks with any dog
Once a week or less	580	22.66		0.74
Several times a week or more	241	22.48			0.00	0.00	0.50	−0.00	0.00	0.32
Frequency walks with own dog
Once a week or less	101	22.64		0.93
Several times a week or more	186	22.56			0.00	0.01	0.84	−0.00	0.01	0.69

Outcome is log10.

Regression adjusted for gender, developmental age, Index of Multiple Deprivation 2007, BMI Standard Deviation Score.

Bold = P < 0.05.

Table 2

Multi‐level multivariable regression models of association between living with a dog and walking a dog, with childhood weight status (International Obesity Task Force cut off for overweight or obese and obese)

Outcome				Crude			Model 1			Model 2 (+ nutrition)
Variable	No, n (%)	Yes, n (%)	Chi‐squared	OR	95% CI	P	OR	95% CI	P	OR	95% CI	P
Overweight or obese
Lives with a dog
No	367 (73.0)	136 (27.0)	0.90
Yes	214 (73.0)	81 (27.0)		0.96	0.68–1.35	0.81	1.04	0.67–1.60	0.86	1.05	0.62–1.77	0.86
Frequency walks with any dog
Once a week or less	373 (74.0)	131 (26.0)	0.93
Several times a week or more	162 (74.3)	56 (25.7)		1.10	0.74–1.63	0.63	0.84	0.53–1.35	0.48	0.95	0.31–2.93	0.92
Frequency walks with own dog
Once a week or less	64 (73.6)	23 (26.4)	0.53
Several times a week or more	118 (69.8)	51 (30.2)		1.27	0.70–2.31	0.44	1.14	0.49–2.67	0.76	1.40	0.43–4.63	0.51
Obese
Lives with a dog
No	470 (93.4)	33 (6.6)	0.24
Yes	269 (91.2)	26 (8.8)		1.37	0.79–2.37	0.27	1.60	0.80–3.20	0.19	1.09	0.43–2.79	0.85
Frequency walks with any dog
Once a week or less	474 (94.1)	30 (5.9)	0.11
Several times a week or more	198 (90.8)	20 (9.2)		1.57	0.86–2.88	0.14	1.66	0.79–3.48	0.18	0.94	0.32–2.77	0.92
Frequency walks with own dog
Once a week or less	81 (93.1)	6 (6.9)	0.27
Several times a week or more	150 (88.8)	19 (11.2)		1.44	0.54–3.86	0.47	1.21	0.36–4.06	0.75	0.60	0.09–3.99	0.60

Model 1 – logistic regression adjusted for gender, developmental age and Index of Multiple Deprivation 2007.

Model 2 – logistic regression adjusted for gender, developmental age, Index of Multiple Deprivation 2007, positive food score and negative food score 19.

Bold = P < 0.05.

Discussion

These analyses offer a small amount of evidence to support the premise that children who live with dogs are fitter, and no evidence that they are at less risk of obesity. The potential association between involvement in dog walking and improved grip strength is feasible, considering that children of this age walking with a dog may at some point hold the leash. Our other tentative findings may be due to confounders associated with both dog ownership and health. For an association between health outcomes and dog walking to be biologically plausible, we would expect to find a positive association between involvement in dog walking and child health rather than a negative association with ownership alone. We found no evidence of an association between dog ownership or dog walking and obesity or overweight. We may lack statistical power to detect a difference; however, this is unlikely, at least regarding weight given exceeding our sample size estimations. Furthermore, we did adjust for nutrition quality as well as social deprivation, as dog ownership is associated with socio‐demographic factors related to poor health 13, 21. Other studies have also found no association between dog ownership and child weight status 4, 6, 8 or a negative association only in some age groups 7. Overall, this suggests that the intensity of physical activity performed when walking a dog might not be vigorous or sustained enough to noticeably impact weight status. Further research is required into the intensity and contexts of physical activity during interactions between children and pet dogs.

Conflicts of interest statement

Prof Dawson, Prof Gaskell, Prof Bundred, Dr German, Dr Coyne and Dr Westgarth report grant funding from WALTHAM and MARS Petcare during conduct of the study. Dr German reports grants, personal fees, non‐financial support and others from WALTHAM (owned by Mars Petcare); grants, personal fees, non‐financial support and others from Royal Canin (owned by Mars Petcare); personal fees and others from Hills Petcare (owned by P&G); and personal fees and others from Nestle‐Purina outside the submitted work. Dr Westgarth reports grants from Medical Research Council, outside the submitted work. Dr McCune reports grants from Mars Petcare UK (sister company) during the conduct of the study, and WALTHAM, who is the main sponsor of the study, pays her salary. Prof Stratton and Dr Boddy have nothing to report.