Associations between Natural Ventilation for the Child's Bedroom during Night and Childhood Asthma in Shanghai, China.

From March 2013 to December 2014, we conducted a case-control study and inspected 454 residences with asthmatic or non-asthmatic children from six districts in Shanghai. Carbon dioxide (CO 2 ) were passively measured 24 hours in the child's bedroom. We took the average concentration of CO 2 during 00:00 to 06:00 as an indicator for the status of natural ventilation in the child's bedroom during night and investigated its association with childhood asthma. A total of 45.6% ( n = 203) residences had CO 2 average concentrations higher than 1000 ppm . The mean CO 2 concentration ± standard deviation was 1123 ± 741 ppm (range: 367 to 4595 ppm ). CO 2 average concentrations in the residences measured in autumn and in summer were significantly lower than measured in winter. No significant differences were found among CO 2 average concentrations among Case group and Control group in total and in different measured seasons. More deeply analyses were warranted. [ABSTRACT FROM AUTHOR]