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Dog Ownership Is the Best Preventive ‘Medicine’ for Patients

  • Lary A. Robinson
    Correspondence
    Requests for reprints should be addressed to Lary A. Robinson, MD, Division of Thoracic Oncology, Moffitt Cancer Center, 12902 Magnolia Drive, Tampa, FL 33612.
    Affiliations
    Division of Thoracic Oncology, Moffitt Cancer Center, Tampa, Fla
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Published:February 20, 2021DOI:https://doi.org/10.1016/j.amjmed.2021.01.033
      Dogs were the first animals to be domesticated, and based on paleogenomic techniques this likely occurred in the Neolithic Period 20,000-40,000 years ago in Europe and Central and East Asia.
      • Botigué LR
      • Song S
      • Scheu A
      • et al.
      Ancient European dog genomes reveal continuity since the Early Neolithic.
      By 14,000 years ago, people were burying loyal dog companions. Over the millennia, dogs have become ingrained in society with 48% of US households having a pet, for a total of more than 89 million pet dogs. Aside from the obvious joy of having a companion dog, there are many known and suspected health benefits of canine ownership.

      Physical Activity

      More than 50% of annual (preventable) deaths result from adverse lifestyle choices, with poor diet and physical inactivity being the most important.

      Centers for Disease Control and Prevention (CDC). Potentially Preventable Deaths from the Five Leading Causes of Death—United States, 2008–2010. Available at: https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6317a1.htm?s_cid=mm6317a1_w#Tab1. Accessed January 19, 2021.

      Regular exercise has been documented to prevent numerous conditions from developing, significantly reducing all-cause mortality, cardiovascular disease, and cancer mortality, and is considered to be effective treatment for 26 chronic conditions (“exercise as medicine”) including depression, hypertension, cognitive decline, osteoarthritis, and type 2 diabetes.
      • Bricca A
      • Harris LK
      • Jager M
      • et al.
      Benefits and harms of exercise therapy in people with multimorbidity: A systematic review and meta-analysis of randomised controlled trials.
      Although the US government's Physical Activity Guidelines for Americans recommends at least 150 minutes of physical activity weekly, less than one-third of Americans meet that recommendation and other countries, such as Taiwan, have only 20% of people meeting that goal.
      • Wen CP
      • Wai JPM
      • Tsai MK
      • et al.
      Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study.
      Dog owners feel obliged to take their canine companions for regular walks, and when studied, dog ownership resulted in a 4 times greater chance of meeting these physical activity guidelines compared with people without a dog
      • Westgarth C
      • Christley RM
      • Jewell C
      • et al.
      Dog owners are more likely to meet physical activity guidelines than people without a dog: An investigation of the association between dog ownership and physical activity levels in a UK community.
      (Figure). Credible evidence demonstrates that owning a dog, with its walking obligation, is strongly associated with a lower risk of cardiovascular conditions and death (hazard ratio = 0.77, 95% confidence interval = 0.73-0.80).
      • Mubanga M
      • Byberg L
      • Nowak C
      • et al.
      Dog ownership and the risk of cardiovascular disease and death–a nationwide cohort study.
      Canadian author O. A. Batista sums up the importance of a canine companion: “A dog is one of the remaining reasons why some people can be persuaded to go for a walk.”

      Allergies and Autoimmune Diseases

      A pandemic of immune-mediated disorders, including allergies, asthma, and autoimmune diseases such as multiple sclerosis, Crohn's disease, lupus, and even autism, continues to accelerate in industrialized countries, such that 1 in 5 children suffers from these maladies. There is mounting evidence that this baffling change in immune system function appears to be a side effect of combating infections with sanitation improvements, vaccines, and antibiotics that have eliminated the microorganisms that co-evolved with us (“old friends”) and have kept our immune system in balance. We have become “too clean,” resulting in a portion of the immune system, the T-helper-2 cells (Th2) that normally pursue parasites and worms, not being counterbalanced by the T-helper-1 cells (who attack bacteria and viruses, which are now less abundant).
      • Okada H
      • Juhn C
      • Feillet H
      • Bach JF
      The ‘hygiene hypothesis’ for autoimmune and allergic diseases: an update.
      This led to an overstimulated immune system (T-helper-1 and -2 deviation) that mistakenly attacks other proteins such as pollen, peanuts, and even the body's own tissues, resulting in allergies and autoimmune diseases. This “hygiene hypothesis” proposes that the modern hygienic environment and dearth of childhood infections and exposure to our usual bacteria leads to a wide spectrum of immune-related disorders.
      • Okada H
      • Juhn C
      • Feillet H
      • Bach JF
      The ‘hygiene hypothesis’ for autoimmune and allergic diseases: an update.
      Children living on farms, especially those younger than 5 years old, who are exposed to bacteria in barns, animal feed, manure, and mud are much less likely to develop allergies or autoimmune diseases compared to nonrural children. This “farming effect” is evident throughout the world and appears to protect children from asthma (odds ratio = 0.48, 95% confidence interval = 0.31-0.76) and allergic diseases. And if the child does not live on a farm, exposure to innocuous microbes that protect against allergic diseases is also obtained by having a dog at home and playing outside in the dirt.
      • Fall T
      • Lundholm C
      • Ortqvist AK
      • et al.
      Early exposure to dogs and farm animal and the risk of childhood asthma.
      Dogs share numerous favorable microorganisms on their coats and mouth with children.

      Mental Health

      The National Academies of Sciences, Engineering and Medicine reported before the coronavirus pandemic that more than one-third of adults 45 years of age and older felt lonely and one-fourth of adults 65 and older were considered socially isolated.
      National Academies of Sciences, Engineering, and Medicine
      Social Isolation and Loneliness in Older Adults: Opportunities for the Health Care System.
      Living alone, loss of friends and family, chronic illness, visual or hearing impairment, and the COVID-19 shelter-at-home environment no doubt exacerbate these statistics. Loneliness and social isolation are significantly associated with a 50% increased risk of dementia, 29% increased risk of heart disease, 32% increased risk of stroke, and a greater risk of all causes of premature death. More severe mental health issues of depression, anxiety, and suicide may follow. In 2018, 48,344 Americans committed suicide with a major depression as the primary risk factor, followed by drug use.
      National Academies of Sciences, Engineering, and Medicine
      Social Isolation and Loneliness in Older Adults: Opportunities for the Health Care System.
      Intuitively, pet ownership would seem to alleviate numerous mental health problems. The published literature on this topic is broad, self-reported, but inconsistent, with significant design limitations. Critically examined, pet ownership surprisingly did not appear to prevent depression across the board with all demographic groups combined.
      • Cline KMC
      Psychological effects of dog ownership: role strain, role enhancement, and depression.
      Nevertheless, dog ownership does reduce depression and has positive effects on well-being in certain subgroups, including single individuals, women, homeless kids, older individuals who suffer a loss of spouse or divorce, elderly women, and people who are more attached to their dog.
      • Cline KMC
      Psychological effects of dog ownership: role strain, role enhancement, and depression.
      ,

      Herzog H. The sad truth about pet ownership and depression. Psychology Today. Available at:https://www.psychologytoday.com/us/blog/animals-and-us/201912/the-sad-truth-about-pet-ownership-and-depression. Accessed January 3, 2021.

      However, pet ownership does not appear to decrease the risk of suicide, although studies suffer from weaknesses of not accounting for the ownership duration, who actually the primary caregiver is, or if the suicide victim just happened to live in a household with a pet.
      • Batty GD
      • Bell S
      Animal companionship and risk of suicide.
      Posttraumatic stress disorder (PTSD) is a common stressor-related condition that adversely affects the mental health and quality of life of nearly 14% of military members and veterans returning from wars. PTSD portends serious comorbidities, including depression, substance abuse, and suicidal tendencies. Aside from conventional treatment with psychotherapy or pharmaceuticals, specially trained PTSD service dogs have been employed. Objective clinical research has shown that compared to usual care, provision of trained service dogs results in significant reductions in PTSD symptoms, reduced depression, and increased social participation.
      • O'Haire ME
      • Rodriguez KE
      Preliminary efficacy of service dogs as a complementary treatment for posttraumatic stress disorder in military members and veterans.
      Emerging evidence suggests that companion animals (dogs and cats) favorably influence the functioning of nonmilitary PTSD populations and drug addiction recovery, as dramatized in the English biographical film A Street Cat Named Bob.
      • Spottiswoode R
      A Street Cat Named Bob.
      Pet therapy (animal-assisted therapy) proves effective in various locations including cancer centers, hospitals, and long-term care and rehabilitation centers. Seeing the unconditional love of a happy, tail-wagging dog brings a smile to anyone's face, and the mere act of touching a dog's fur causes release of the feel-good brain hormone oxytocin in the human. Amazingly oxytocin is also released in the dog who enjoys human touch.
      • Petersson M
      • Uvnäs-Moberg K
      • Nilsson A
      • et al.
      Oxytocin and cortisol levels in dog owners and their dogs are associated with behavioral patterns :an exploratory study.
      No doubt the vintage colloquial term “petting” was coined to refer to romantic physical contact between 2 people because that same pleasure hormone is also released!

      Recommendations

      Should health care providers recommend dog ownership to their patients? Yes, of course, but with several caveats. Potential dog owners need to realize that pet ownership carries a 10- to 15-year commitment. Although most people outlive their dogs, older people with multiple comorbidities should make plans for the care for their animal should they die first. Because dogs rapidly become a treasured member of the family, their inevitable demise may be as stressful as losing any relative.
      The evolution from an aggressive, reclusive wolf to the dazzling variety of always-attentive, human-centered furry buddies is truly remarkable. And for the spiritually oriented reader, dogs are a gift obviously placed on the Earth for 1 primary reason: to take care of us humans–our physical and mental health. And it is not coincidental that “dog” is “God” spelled backward.
      • Cameron WB
      A Dog's Journey.
      Whether they are terrestrial angels without wings (as many believe) or a highly-evolved species of wolf with an instinctive love of humans, their well-documented mental and physical health benefits should strongly encourage physicians to recommend dog ownership to their patients.

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        Ancient European dog genomes reveal continuity since the Early Neolithic.
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