Discussion
depression, pain, cot, musculoskeletal pain
EVENT, OBESE
In this study, we found that bubble wrap could not improve body pressure concentration, as with an air mattress, when using a cardboard bed at an evacuation shelter. However, subjective firmness and comfort were improved using the bubble wrap.No cot had been installed in Japanese evacuation shelters, and evacuees had to sleep on the floor with a futon or mattress until the Great East Japan earthquake. Since then, cardboard beds have been installed in evacuation shelters to protect evacuees from various health problems when a large-scale disaster occurs. Previous studies on healthy subjects have reported that they are more likely to develop musculoskeletal pain when lying on the floor than when lying on a mattress and that body-mattress contact pressure and contour area when lying on a cardboard bed without any mattress do not differ from that when lying directly on the floor (However, an excessively firm mattress could cause back pain because the weight is concentrated on the buttocks and shoulders. Although four stacked layers of bubble wrap were used in this study, they may not have been sufficient to disperse human weight because the particle size of a single bubble was only 10 mm. The amount of filled air in a single bubble also affects the rebound. Therefore, the capacity of body pressure dispersion by bubble wrap can be improved by changing the air-filling rate and the size of the air bubbles. It will be necessary to investigate how bubble wraps with different numbers of folded layers and bubble sizes will affect body pressure distribution. We will also obtain data on the effects of bubble wrap with different air-filling volumes on body pressure distribution. However, subjective firmness and comfort were improved by laying a bubble wrap on a cardboard bed. In the event of a large-scale disaster, some evacuees were forced to spend months in shelters, but the subjects were asked to lay on a bed for a very short time in this study. The amount of time spent lying down is an essential factor in influencing the strain on the musculoskeletal system. Therefore, long-term use of bubble wrap may affect the incidence of back pain in evacuees. Chronic pain, including back pain, is a known risk factor for depression (This study has several strengths. First, to our knowledge, this randomized controlled crossover trial is the first study aiming to improve evacuees’ body pressure concentration in a shelter environment where futons or any mattresses laid on a cardboard bed cannot be provided. Second, our results suggest that personal stockpiling or a building system to provide mattresses for evacuees may contribute to maintaining evacuees’ health when a large-scale disaster occurs.However, this study had some limitations. First, obese, or older people have a higher risk of back pain, but our subjects were mostly young females who were not obese. As the results in high-risk individuals may differ from ours, we adjusted for these effects by entering sex and BMI as covariates in our linear mixed model. Second, we considered that the carryover effect of body pressure distribution was not strong; therefore, we set the washout period to only 10 min. However, sequence and period (2nd–3rd), entered as fixed effects, did not significantly affect our results. The average body contact pressure was calculated using a maximum peak pressure of 110 mmHg. Therefore, localized peak pressures exceeding this value were not recorded and the actual average pressure may be higher than shown. In this study, the same size bubbles were used without taking body shape into account. However, the appropriate height of the bubble is likely to vary depending on variables such as weight, gender, and age. Individual factors should be considered when selecting a mattress of appropriate thickness.