Dog Ownership and Cardiovascular Disease

The relationship between pet ownership and human health has been studied extensively; however, the effect of dog ownership on human health has had conflicting results. The overall aim of this research project was to investigate the impact of dog ownership, and the death of the dog, on human cardiovascular health and all-cause mortality. Study I was a population-based study investigating the association between dog ownership with the risk of cardiovascular disease (CVD) and death. Of 3,432,153 individuals included, dog ownership (13.1%) was associated with a lower risk of CVD- and all-cause death by 23% and 20%, respectively. In single-person households, there was an inverse association between dog ownership and incident CVD, as well as a stronger inverse association with CVD-death and all-cause death. Study II was a population-based study investigating the association between dog ownership and initiation of treatment for cardiovascular risk factors in 2,026,865 adults. Dog ownership (14.6%) was associated with a slightly elevated risk of initiating treatment (2%) for hypertension and dyslipidaemia, but not for diabetes mellitus. However, some evidence for residual confounding was found. Study III investigated the risk of death after hospitalization for a first-ever acute myocardial infarction (n=181,696) or first-ever ischemic stroke (n=157,617) in two population-based cohorts. Dog ownership was associated with a 20% to 24% lower risk of all-cause mortality and CVD-death, respectively. In Study I-III, ownership of hunting breed dogs was associated with the lowest risk of the outcomes, while owning dogs of mixed pedigree was associated with worse cardiovascular health. Study IV found evidence of an increased risk of CVD after the loss of a life-insured pet (dog or cat; n=147,251) during the first week, 3-6 months after and 6-12 months after pet-loss. This thesis has used the Swedish population and health registers to investigate the relationship between various aspects of dog ownership and cardiovascular risk. By using defined, quantifiable end-points and robust statistical methods, this project has made an important contribution to the body of research underlying the positive relationship between dog ownership and cardiovascular health, paving the way for further research into causal mechanisms