Objective To study the association between dog ownership and cardiovascular risk factors.
Design A nationwide register–based cohort study and a cross-sectional study in a subset.
Setting A cohort of 2 026 865 participants was identified from the Register of the Total Population and linked to national registers for information on dog ownership, prescribed medication, hospital admissions, education level, income and country of birth. Participants were followed from 1 October, 2006, to the end of the study on 31 December, 2012, assessing medication for a cardiovascular risk factor, emigration and death. Cross-sectional associations were further assessed in 10 110 individuals from the TwinGene study with additional adjustment for professional level, employment status, Charlson comorbidity index, disability and tobacco use.
Participants All Swedish residents aged 45–80 years on 1 October, 2006.
Main outcome measures Initiation of medication for hypertension, dyslipidaemia and diabetes mellitus.
Results After adjustment for confounders, the results indicated slightly higher likelihood of initiating antihypertensive (HR, 1.02; 95% CI, 1.01 to 1.03) and lipid-lowering treatment (HR, 1.02; 95% CI, 1.01 to 1.04) in dog owners than in non-owners, particularly among those aged 45–60 years and in those owning mixed breed or companion/toy breed dogs. No association of dog ownership with initiation of treatment for diabetes was found in the overall analysis (HR, 0.98; 95% CI, 0.95 to 1.01). Sensitivity analyses in the TwinGene cohort indicated confounding of the association between dog ownership and prevalent treatment for hypertension, dyslipidaemia and diabetes mellitus, respectively, from factors not available in the national cohort, such as employment status and non cardiovascularchronic disease status.
Conclusions In this large cohort study, dog ownership was associated with a minimally higher risk of initiation of treatment for hypertension and dyslipidaemia implying that the previously reported lower risk of cardiovascular mortality among dog owners in this cohort is not explained by reduced hypertension and dyslipidaemia. These observations may suffer from residual confounding despite access to multiple important covariates, and future studies may add valuable information.
- cardiac epidemiology
- general diabetes
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Contributors TF conceived the study and acquired funding. MM, AE, EI, JS and LB contributed to the design of the study. TF acquired the national data and PKEM is responsible for the Swedish Twin Registry data. MM performed data cleaning. MM and TF ran statistical analyses. MM drafted the manuscript and all authors reviewed the manuscript.
Funding The study was funded by the Agria Research Foundation and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS), grant number 2013-1673. TF has personal funding from the Goran Gustafsson foundation. The Swedish Twin Registry is managed by Karolinska Institutet and receives funding through the Swedish Research Council under the grant no 2017-00641.
Competing interests EI is a scientific advisor for Precision Wellness and Olink Proteomics for work unrelated to the present project.
Ethics approval The regional ethical review board in Stockholm, Sweden, approved the study (national study: 2012/1114-31/2, with amendment 2013-1687-32; TwinGene: 2007/644-31/2 and 2016/1392-31/1).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The register data that support the findings of this study were made available by record-linkage with data from Statistics Sweden, the National Board of Health and Welfare, the Swedish Kennel Club, Swedish Board of Agriculture and the Swedish Twin Register. Restrictions apply to the availability of these data, which were used under license and ethical approval for the current study, and so are not publicly available. Data are however available from the authors upon reasonable request and with permission of the Regional Ethical Review Board in Stockholm, Sweden.
Presented at The results of this study were previously presented as a poster at the World Congress or Cardiology and Cardiovascular Health 2018 and an abstract was published in Global Heart Volume 13, Issue 4, December 2018, Page 483.
Patient consent for publication Not required.
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