Posttraumatic Stress and Lifestyles Are Associated with Natural Killer Cell Activity in Victims of the Hanshin-Awaji Earthquake in Japan,

Background. The relationships among mental health status, lifestyle, and natural killer (NK) cell activity, which plays important roles in the immune surveillance of tumors and viral infections, were investigated in victims of the Hanshin-Awaji Earthquake. Methods. About 1 and 1/3 years after the earthquake, 155 male workers who experienced the event were administered questionnaires concerning their unhealthy mental status, such as symptoms of posttraumatic stress disorder (PTSD), lifestyles, and demographic variables. Peripheral blood was taken from all of them to measure NK cell activity. Results. Subjects who had PTSD symptoms showed lower NK cell activity than those without symptoms. Subjects with positive lifestyles showed higher NK cell activity than those with poor or moderate lifestyles. When subjects were divided into four groups by lifestyle and PTSD symptoms, subjects with positive lifestyles and few or no PTSD symptoms showed the highest NK cell activity among the four groups. The other three groups were subjects with positive lifestyles but many PTSD symptoms; subjects with poor or moderate lifestyles and many PTSD symptoms; and subjects with poor or moderate lifestyles and few or no PTSD symptoms. Conclusion. PTSD symptoms and lifestyles were associated with NK cell activity in the earthquake victims.