Friday February 17 2012
Do walkers get dogs or do dogs make us into walkers?
“Dogs are a woman’s best friend too!” according to the Daily Mail, which said that research has ‘proved’ that expectant mothers with a pet pooch are more physically active than those without one.
The research examined data on over 11,000 pregnant women to look at links between pet ownership and the type of physical activity they undertook. One-quarter of the women owned a dog, and those who owned a dog were more likely to be physically active at least once a week, and to achieve three or more hours of physical activity each week. When broken down by type of activity, the one that dog owners did more of than women without a dog was brisk walking.
It is not surprising that women who own a dog would walk more regularly, However, before women go out and get themselves a canine companion, it should not be assumed that having a dog causes people who would otherwise be sedentary to be more active. It could be that people who have more active lifestyles are also more likely to have a dog.
While regular brisk walking is free and a good form of cardiovascular exercise for pregnant women, you do not need a canine companion to do it – you can just take yourself and avoid cleaning up dog droppings.
In pregnancy, both NICE and the Department of Health advise that beginning or continuing a moderate course of regular exercise is beneficial but advise that pregnant women avoid potentially dangerous, high-impact or contact sports.
Where did the story come from?
The study was carried out by researchers from University of Liverpool and other institutions in the UK and US.
Participants were drawn from the Avon Longitudinal Study of Parents and Children (ALSPAC), a long-running research project supported by the Medical Research Council, Wellcome Trust, UK Department of Health, Department of the Environment, Department of Education and the Environment, National Institutes of Health, and a variety of medical research charities and commercial companies.
This specific study on the role of dogs in pregnancy was funded by a grant from the WALTHAM Centre for Pet Nutrition - a subsidiary of Mars Petcare, which manufactures a range of pet foods including Pedigree Chum. The study was published in the peer-reviewed journal Plos One.
What kind of research was this?
This was an analysis of dog ownership and health in pregnant women who were taking part in the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort. Specifically, the research looked at the pregnant woman’s self-reported physical activity, pre-pregnancy BMI and looked at whether there was any relationship between these factors and whether the women owned a dog.
The study was cross-sectional, meaning it measured these factors at a single point in time rather than following participants to see how they progressed over a period. Although the study technically did assess the participants at two points during their pregnancy, these were only a few months apart and do not provide any meaningful data on women’s health and fitness levels before and after getting a dog. On this basis, it should be seen as providing cross-sectional data.
Regular physical activity is known to contribute to maintaining a healthy weight and wellbeing and it is not surprising that women who own a dog would take more regular activity.
However, given that the study only assessed the participants at a single point in time, it can provide only limited conclusions; that is, it can show us whether owning a dog is associated with good health, but not that the dog is the cause of someone’s health status. We cannot tell whether having a dog causes people who would otherwise be sedentary to be more active or whether people who have more active lifestyles are more likely to get a dog.
What did the research involve?
This study was an analysis of the long-running ALSPAC study started in the early 1990s to look a range of health and development factors among babies born in the Avon area of south-west England. The ALSPAC study recruited 14,541 pregnant women from Avon who were due to give birth between April 1991 and December 1992. This sub-study on pet ownership excluded any multiple births such as twins and looked at only the 14,273 women who went on to give birth to single babies.
During pregnancy, the women were assessed using questionnaires and clinical assessments. At 18 and 32 weeks of pregnancy, women were questioned on any regular physical activity that they took such as housework, gardening, brisk walking, jogging, cycling, aerobics, antenatal classes, ‘keep fit’, yoga, squash, tennis/badminton, swimming or weight training.
Options for response were seven or more hours a week, two to six hours, less than one hour, or never. The mother’s pre-pregnancy body mass index (BMI) was calculated from her self-reported height and weight. At enrolment the women had also been asked if they had any pets, and if so, what type of pet.
The researchers analysed how ownership of different pets related to:
- whether women did physical activity at least once a week or none
- whether they did three or more hours of exercise a week, or less than three hours
- the number of hours of different types of activity women did each week
- whether women were normal weight (BMI<25), or overweight or obese
The researchers then adjusted for potential confounders that could influence the relationship between physical activity and of pet ownership, including:
- maternal education
- maternal social class
- working during pregnancy
- maternal age at delivery
- number of people in household
- previous children
- house type
- whether the pregnant woman had pets as a child
What were the basic results?
The study analysis only looked at the 11,466 women who provided details on both physical activity and pet ownership during pregnancy. During pregnancy, 58% of these pregnant women owned one or more pets and 25% had one or more dogs. At 18 weeks of pregnancy, almost 70% of all pregnant women assessed engaged in any form or physical activity at least once a week, and 50% of all women took part in three or more hours of activity a week.
Women who owned a dog were 27% more likely to participate in physical activity at least once a week than those who did not have a dog (odds ratio [OR] 1.27, 95% confidence interval [CI] 1.11 to 1.41). Dog owners were also 53% more likely to achieve three or more hours of activity a week (equivalent to 30 minutes a day on most days of the week: OR 1.53, 95% CI 1.35 to 1.72).
When broken down by type of activity, dog owners were more likely to participate in brisk walking two to six hours a week (OR 1.43, 95% CI 1.23 to 1.67) or seven or more hours a week (OR 1.80, 95% CI 1.43 to 2.27), but they found no association between dog ownership and any other type of activity.
Similar associations were seen at 32 weeks of pregnancy.
There was no link between dog ownership and ‘weight status’(being of ideal weight, overweight or obese).
How did the researchers interpret the results?
The researchers conclude that in their study pregnant women who had dogs were more active than those who did not own dogs, principally through walking. They consider that, as walking is a low-risk exercise, it should be investigated whether encouraging pregnant women to participate in dog walking is useful as part of a broader strategy to improve activity levels in pregnant women.
This cross-sectional study looked at over 11,000 women who were pregnant in 1991 and 1992 and questioned them on their levels of physical activity and pet ownership. Women who owned a dog were found to do more brisk walking than those without.
It is not surprising that women who own a dog would walk more regularly. However, the study only looked at health and dog ownership within a narrow period, so limited conclusions can be drawn from this observational research. It is not possible to say whether having a dog causes people who would otherwise be sedentary to be more active, or whether people who have more active lifestyles are more likely to choose having a dog.
Although the researchers adjusted for some potential factors that can influence both levels of activity and dog ownership (for example, socioeconomic status or past dog ownership), it is still difficult to pick apart this relationship.
At all stages in life, regular physical activity and a healthy balanced diet are known to contribute to maintaining a healthy weight, increasing wellbeing and reducing the risk of many chronic diseases.
The National Institute for Health and Clinical Excellence (NICE) advises that beginning or continuing a moderate course of exercise during pregnancy is not harmful, but advises avoiding potentially dangerous, high-impact or contact sports. The Department of Health also advises women to keep up normal daily physical activity or exercise for as long as is comfortable, as the more active and fit they are during pregnancy, the easier it will be to adapt to pregnancy weight gain, cope with labour and get back into shape after the birth.
Similarly, the Department of Health advises against potentially dangerous activities such as contact sports, horse riding and gymnastics.
Regular brisk walking is free and a good form of cardiovascular exercise and a good activity choice during pregnancy. However, while you can get benefits from regular walking, you do not need a dog to do it.
Analysis by Bazian