[Relationship between daily mean temperature and emergency department visits for respiratory diseases: a time-series...

To quantitatively evaluate the influences of daily mean air temperature (DMT) on Emergency Department Visits (EDVs) for the respiratory diseases.

The EDV data from medical records for respiratory diseases in Peking University Third Hospital between January 2004 and June 2009 were collected. The data of the air pollutants (SO(2), NO(2) and PM(10)) and meteorological factors at the same time periods were also collected from the local authorities of Beijing. Time-series analysis and generalized additive models (GAM) were used to explore the exposurrre-response relationship between DMT and EDVs for respiratory diseases.

A total of 35 073 patients [males 14 707(41.93%,14 707/35 073), females 19 122(54.52%,19 122/35 073) and gender missing 1 244(3.55%, 1 244/35 073)] EDVs for respiratory diseases were included. The relationship between DMT and EDVs for the respiratory diseases was mainly of "V" shape, the optimum temperature(OT) was about 4 °C and the effect of DMT was significant with a 0-3 day lag structure for most of the models. When DMT≤OT, each 1°C decrease in DMT corresponded to 3.75% (95% CI of RR: 0.938 3-0.965 3), 3.10% (95% CI of RR:0.949 2-0.989 1), 4.09% (95% CI of RR:0.940 7-0.977 8) increase of EDVs for the overall, male, and female, respectively. When DMT>OT, the value caused by each increase in 1°C in DMT was 1.54% (95% CI of RR:1.006 6-1.024 3), 1.80% (95% CI of RR:1.005 3-1.030 9), and 1.51 (95% CI of RR:1.003 2- 1.027 2), respectively. The effect was statistically significant within the 0-3 day lag. When DMT≤OT, the effect was stronger for the older people, while the effect was strongest for the 45-59 years old people.

The relationship between DMT and EDVs for respiratory diseases is mainly of "V" type, with an optimum temperature of 4 °C.Both DMT decrease when DMT≤OT and increase when DMT>OT correspond to different increase of EDVs for respiratory diseases. Low DMT has stronger effect than high DMT. Different age group and gender have different effects.