Association between housing damage, present bias and delayed-onset post-traumatic stress symptoms among older adults 9 years after a natural disaster.

Background: Previous studies suggest that experience of natural disasters may heighten present bias. Research also suggests that impaired self-control (in particular, heightened present bias) could be linked to delayed-onset post-traumatic stress symptoms (PTSS) among survivors of natural disasters. We examined a hypothesis that the association between disaster experiences and delayed-onset PTSS is mediated through present bias among older survivors of the 2011 Japan earthquake and tsunami.

Methods: The baseline survey was conducted for older adults who lived in a city located 80 km west of the epicentre 7 months before the disaster. Approximately 2.5 and 8.5 years after the disaster, we surveyed older survivors to assess the trajectory of PTSS (2230 participants). We implemented analyses by three analytical groups: (1) resilient versus delayed-onset, (2) resilient versus improved and (3) resilient versus persistent.

Results: Logistic regression models showed that major housing damage was linked to raised present bias in all analytical groups (OR 2.47, 95% CI 1.04 to 5.87; OR 2.75, 95% CI 1.20 to 6.29; OR 2.65, 95% CI 1.15 to 6.10, respectively). The present bias, however, was significantly associated with only delayed-onset PTSS (OR 2.05, 95% CI 1.14 to 3.69). In the group of resilient versus delayed onset, housing destruction was also associated with delayed-onset PTSS (OR 2.44, 95% CI 1.11 to 5.37), and the association was attenuated by present bias (OR 2.36, 95% CI 1.07 to 5.18).

Conclusions: Present bias could mediate the association between housing damage and delayed-onset PTSS among older survivors of a natural disaster.