A study involving U.S. military veterans diagnosed with post-traumatic stress disorder (PTSD) found that their heart rates were lower during sleep when they were in close proximity to a service dog, compared to nights without one. This effect was more significant among those with more severe PTSD symptoms. The study was published in Biological Psychology.
PTSD is a mental health condition that can develop in individuals who have experienced or witnessed a traumatic event. It is characterized by a range of symptoms, including intrusive and distressing memories, nightmares, flashbacks, heightened anxiety, and emotional numbing. People with PTSD often avoid reminders of the trauma, have negative changes in mood and cognition, and experience heightened arousal and reactivity, such as being easily startled or irritable.
Persons diagnosed with PTSD have an elevated risk of cardiovascular disease. They are also more likely to have a poor diet, smoke tobacco, have heightened blood pressure, which are all risk factors for cardiovascular disease. This has attracted researchers to try to develop new methods that could alleviate these risks in individuals with PTSD.
A promising avenue of research is the use of dogs. A group of studies conducted in different parts of the world reported that dog owners have reduced risks of cardiovascular disease and of dying from its complications. The risk reductions were particularly high in individuals living alone (with a dog compared to living alone without a dog).
Study author Steven H. Woodward and his colleagues wanted to examine whether dog ownership could reduce the risk of cardiovascular disease in individuals with PTSD. They focused on heart rate measured during sleep. Elevated heart rates during sleep and at waking are well-established predictors of cardiovascular disease. However, heart rate at waking can vary widely due to emotional arousal, recent activity, food intake and other factors. This is not the case with heart rate during sleep, which is why study authors chose to follow this indicator in their study.
Participants were 45 U.S. military veterans undergoing residential treatment for PTSD at the Trauma Recovery Program at the VA Palo Alto Health Care System. Their typical length of stay was 100 days. These veterans, primarily from the Iraq and Afghanistan wars, ranged in age from 25 to 71.
During their time in the trauma recovery program, the participants engaged in an intensive service animal training program, providing preliminary training to service dogs in collaboration with the non-profit organization, Paws for Purple Hearts. Professional trainers from this organization supervised the veterans.
Each dog was assigned two trainers. These trainers alternated weeks for dog custody—one week with one trainer and the next week with the other. Participants training the same dog did not share accommodations. During their week of custody, the trainer would maintain close contact with the dog throughout the day and night. On the alternate weeks, their contact with the dog was minimal.
To assess the severity and frequency of PTSD symptoms among participants, the researchers utilized the Structured Clinical Interview for DSM-5 and the Clinician Administered PTSD Scale for DSM-5. They also employed mattress actigraphy to monitor participants’ heart rates during sleep, collecting data for an average of 24 nights per participant.
The study’s findings revealed that 70% of participants also had major depressive disorder, 61% had alcohol use disorder, 30% struggled with substance abuse, and 76% were either overweight or obese.
The presence of the service dog did not affect the time when participants went to sleep, nor the time they spent sleeping. The mean heart rate during sleep was 64.6 beats per minute. Heart rate during sleep tended to increase as the study progressed. However, this progressive increase was much smaller for nights when participants were with a dog.
Initially, participants with service dogs exhibited slightly higher heart rates than those without. By the study’s conclusion, the heart rate on nights with a dog saw a minor increase to just above 64 beats per minute. In contrast, the average heart rate on nights without a dog was around 66.3 beats per minute. The service dog’s impact on heart rate was more pronounced among participants with severe PTSD symptoms.
“In summary, this study observed 1) a lowering of sleeping heart rate with service dog contact not attributable to preintervention sample bias, 2) accentuation of that effect in participants at higher levels of PTSD severity and a converse attenuation or even reversal at lower levels PTSD severity, 3) an unexpected increase in sleeping heart rate over the course of study participation, and 4) attenuation of that effect in association with service dog contact. Later in study participation, sleeping heart rate was approximately 2 bits per minute lower on nights in contact with a familiar service dog over all participants,” the study authors concluded.
The study provides valuable insights into health benefits from service dogs for individuals with PTSD. However, it also has limitations that need to be considered. Notably, the number of participants of the study was very small, they were all males, and military veterans. Results on other demographic categories might not be the same.
The paper, “Heart rate during sleep in PTSD patients: Moderation by contact with a service dog”, was authored by Steven H. Woodward, Andrea L. Jamison, Sasha Gala, Catherine Lawlor, Diana Villasenor, Gisselle Tamayo, and Melissa Puckett.
