A recent study suggests that dogs fed once a day have fewer physical health issues and better cognitive scores compared to dogs fed more frequently.
Decades of research in controlled settings has found links between diet and aging in rodents; however, connections aren’t as clear in settings outside the lab for animals or humans. Authors of the study realized that data from the Dog Aging Project, which has collected information on thousands of companion dogs, presented a unique opportunity to study diet in a large animal that shares human environments.
“We weren’t confident at all that we would see any differences in dogs’ health or cognition based on feeding frequency. I think we would have been excited to see an association between feeding frequency and health in just one domain. I was surprised to see associations in so many domains,” said senior author Kathleen Kerr, a professor of biostatistics in the University of Washington School of Public Health.
Kerr led development of the study’s analysis plan, which included decisions to expand the initial focus on cognition and incorporate other health conditions such as skin, orthopedic, kidney, urinary, liver, cardiac, and neurological disorders.
One of the statistical challenges the study faced involved pure-breed dogs. Dogs in the Dog Aging Project are almost evenly split between mixed-breed and pure-breed dogs. However, the pool of pure-breed dogs represented more than 200 different breeds, and only a few breeds have a lot of dogs in them.
“There are important differences among breeds, most obviously genetic differences but also potential environmental differences – dogs of different breeds might tend to live different dog lifestyles. Put all of that together, it is compelling to want to control for breed in the analysis, meaning to compare dogs with different feeding frequency of the same breed. This runs into known statistical issues for analyzing binary (yes/no) outcomes because with so many breeds effect estimates would tend to be exaggerated,” said Kerr.
Mixed-breed dogs presented their own challenges.
“The best information we have about mixed-breed dogs is their size, because size is such an important factor in dog health and longevity. Larger dogs and smaller dogs have different risks of health conditions and we didn’t want to pretend that mixed-breed dogs are a homogeneous group, so our analysis compared mixed-breed dogs with different feeding frequency but similar size,” said Kerr.
Zihan Zheng, a student in the Master of Biostatistics Capstone program, is a study co-author. She conducted statistical analysis and says her work included, but was not limited to, cleaning and merging data, constructing new variables, performing the primary analysis, interpreting analytic results, and creating key tables and figures for publication.
“It was a wonderful experience working with Professor Kerr and the other team members. I was impressed and inspired by their passion and conscientiousness, and it was very exciting to see the interesting results!”
“Zihan was fully engaged in the project and the science behind it from the beginning. Some of the methods we used in the project were new to her, but she took every challenge in stride,” said Kerr.
While the results are intriguing, Kerr said the evidence base is not strong enough to impact the care and feeding of dogs, and that people should not change the way they feed their dogs based on this study.
“The study is a small step toward understanding whether effects seen in laboratory animals generalize to dogs who live in highly varied, non-controlled environments. An important next step for the Dog Aging Project will be to re-visit our study questions in the future, after the study has followed dogs over time,” said Kerr.
The Dog Aging Project continues to welcome new dogs of all ages, sizes, and breeds to the pack. Nominate your dog for the project.
- Deb Nelson, UW Biostatistics Communications
