The beneficial effect of pet ownership on the physical, social and psychological health of people has been well documented (Friedmann, 1995; Headey, 2003; Katcher, 1981; Katcher & Friedmann, 1982; McNicholas et al., 2005). Contact with companion animals during childhood is likely to have effects on child development , and therefore ownership of pets (and the different types) is also likely to be of significance to child development.

Most studies of health benefits of pets are cross-sectional. Consequently it is difficult to determine whether these health benefits result from pet ownership or whether it is healthier people who choose to own pets. The relatively few longitudinal studies indicate the direction of causality is from pet to owner (Serpell 1991; Headey & Grabka 2007). Longitudinal national representative surveys in Germany and Australia show that pet owners make about 15% fewer annual doctor visits than non-owners (Headey & Grabka 2007). The relationship remains statistically significant after controlling for gender, age, marital status, income and other variables associated with health.

Pet ownership data was collected from the ALSPAC cohort up to age 10 years. This was using the carer questionnaire. At gestation, and 8 months, the number of cats, dogs, rabbits, rodents, birds and other pets were collected. This was then expanded to include categories fish, tortoises and turtles, and any remaining pet types as 'other pets', for the rest of the data collection. These data were collected at 21, 33, 47, 85, 97 and 122 months.

Our team at Liverpool University are currently using the ALSPAC data to explore if there is any association between pet ownership, and obesity, using measures of BMI, fatness and physical activity. This project is funded by WALTHAM(registered trademark) . The data is currently limited to up to 10 years, but it is plausible to consider that there may also be interesting effects beyond this time. In fact, the teenage years may be particularily important in relation to pet ownership, as this is a time when children become more independent and responsible, and for example may walk their dog on their own. For this reason we propose that questions on pet ownership be re-introduced to ALSPAC data collection. The data will be of use not only to researchers interested in obesity and physical activity, but those interested in the effects of the human-companion animal bond in relation to many different aspects of physical and psychological health and development.

To our knowledge, there have been no detailed longitudinal studies decribing pet ownership trends during childhood and teenage years, despite the knowledge that pets, in particular dogs, are more likely to be found in households with school age children that those without (Westgarth et.al., 2007). It is thought that pet ownership is associated with factors such as household type and socioeconomic status, and so there is high potential for confounding in studies of health-related factors. In addition, the factors associated seem to vary with specific pet type, and so the effects of, for example, cat, dog, and small animal ownership need to be investigated separately (Westgarth et.al., In Press). For these reasons it is well worth fully characterising aspects of pet ownership in childhood years using a large and detailed resource such as ALSPAC.

Our proposal to re-introduce pet ownership questions back into the ALSPAC questionnaire at 18 years can be done in a number of formats.

1) Firstly, we would like to re-introduce the basic questions relating to pet ownership, namely - Do you own a pet? And how many cats, dogs, rabbits, rodents, birds, fish, tortoises and terrapins, and other pets, do you own?

2) Because there is a data gap from age 10 to 18, we also propose attempting to inform this gap by asking children to recall whether they owned pets at age 14, and which types. We do not imagine recall bias to be a significant problem, because we imagine that people can reliably remember whether or not they owned a type of pet. They may not be able to recall 'numbers of' a particular pet as accurately though, and therefore a simple indication of pet type is probably most appropriate.

3) Because we have reliable pet ownership information up to 10 years, it would be possible to test the validity of asking respondents to recall pet ownership, by asking them what types of pet they owned up to 10 years old, and then checking this against the data already collected. Surveys of pet ownership are often cross-sectional and ask respondents to recall previous pet ownership, and so a measure of the validity of such an approach would be extremely useful in the field of Human-Animal Interaction research. It would also inform the results from 2) above.

4) The data on pet ownership in the ALSPAC resourse is limited, albeit of large numbers. This would be an opportunity to further explore particular aspects and attitudes relating to pet ownership, that may further elucidate any impact that pet ownership has on health.

In particular:

How much the child is involved in the day-to-day responsibilities and care of the pet.

For example, if they own a dog, do they walk it and how often. This can be compared with the reported frequency of activities such as walking from all children, in particular those not owning a dog.

If they own a dog, what breed, and size of dog.

Measures of attachment to the pet (measured using a published and validated pet attachment scale), as this may affect the impact of owning a pet on a particular individual.

WALTHAM(registered trademark) is a leading scientific authority in pet nutrition and well-being. For almost 50 years they have researched the nutritional and behavioural needs of companion animals and their benefits to humans. In 2008, WALTHAM(registered trademark) formed a public-private partnership with the National Institutes of Health (NIH) in the USA to encourage research in the field of HAI and to help grow the field. In particular they acknowledged the uses of birth cohort studies such as ALSPAC. Sandra McCune directs the Human-Animal Interaction research programme at the WALTHAM(registered trademark) Centre for Pet Nutrition where she manages a large portfolio of HAI research projects. WALTHAM(registered trademark) has identified the role of pets in physical activity and obesity as a research priority for the programme and are keen to support this study.

References

Friedmann, E. (1995). The role of pets in enhancing human well-being: physiological effects. In The Waltham Book of Human-Animal Interaction: Benefits and Responsibilities of Pet Ownership, pp. 33-53. Edited by I. Robinson. Oxford: Elsevier Science Ltd.

Headey, B. (2003). Pet ownership: good for health? Medical Journal Of Australia 179, 460-461.

Headey, B & Grabka, M.W. (2007) Pets and human health in Germany and Australia: National Longitudinal results. Social Indicators Research (2007) 80: 297-311.

Katcher, A. H. (1981). Interactions between people and their pets: form and function. In Interrelations between people and pets, pp. 41-67. Edited by B. Fogle. Springfield: Charles C. Thomas.

Katcher, A. H. & Friedmann, E. (1982). Potential health value of pet ownership. California Veterinarian 36, 9-13.

McNicholas, J., Gilbey, A., Rennie, A., Ahmedzai, S., Dono, J.-A. & Ormerod, E. (2005). Pet ownership and human health: a brief review of evidence and issues. BMJ 331, 1252-1254.

Serpell,J. (1991) Beneficial effects of pet ownership on some aspects of human health and behaviour Journal of the Royal Society of Medicine Volume 84 December: 717-720

Westgarth, C., Pinchbeck, G. L., Bradshaw, J. W., Dawson, S., Gaskell, R. M. & Christley, R. M. (2007). Factors associated with dog ownership and contact with dogs in a UK community. BMC Vet Res 3, 5.

Westgarth, C., Pinchbeck, G. L., Bradshaw, J. W., Dawson, S., Gaskell, R. M. & Christley, R. M. (In Press). Factors associated with cat ownership in a UK community. Vet Record.