PDS 66: Climate change, Exhibition Hall (PDS), Ground floor, August 28, 2019, 1:30 PM - 3:00 PM Background/Aim: There has been growing concern about the effects of heat wave on health. However, the effect on the health indicators for vulnerable group has rarely been examined. We aimed to investigate the acute effects of heat wave on body temperature and blood pressure of elderly individuals living in poor housing conditions in rural areas. Methods: Indoor temperature, body temperature (BT), blood pressure, and sleep disturbance were repeatedly measured up to six times for each 104 elderly individuals living in four southern rural areas in South Korea during heat waves in 2018. Changes in the BT, systolic blood pressure (SBP) and diastolic blood pressure (DBP) according to variations in the indoor and outdoor temperature were analyzed using linear mixed effect models controlling for age, sex, drug use, and smoking. We also analyzed the health effects of heat wave from socioeconomic status. Results: The average of indoor temperatures measured during the study period was 30.5°C (range, 22.9~38.3°C) and that of daily maximum outdoor temperature 34.5°C (range, 29.5~37.5°C). Indoor temperature was higher in low-income group than relatively high-income group. BT increased by 0.05°C [95% confidence interval (CI), 0.03 to 0.06°C] with an increase in the indoor temperature of 1°C. The effect of increased indoor temperature on BT was greater in the elderly with hypertension and sleep disturbance. DBP generally decreased with increase in indoor temperature, while the DBP decrease in the elderly with hypertension showed a statistical significance [-0.41 mmHg (95% CI, -0.02 to 0.80 mmHg) per 1°C]. SBP increased as the indoor temperature increased, particularly for the elderly without air conditioner. Conclusions: The elderly with poor house condition are directly exposed to heat waves, while their vital signs respond sensitively to temperature increase indoors. More active strategies to cope with increasing heat wave are required, particularly for vulnerable group.