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The effect of ambient temperature on the onset of acute Stanford type B aortic dissection.

BACKGROUND
The aim of this work was to study the associations between weather conditions and the occurrence of type B acute aortic dissections (ABAD).


PATIENTS AND METHODS
This study was a retrospective review of all ABAD cases between January 1st, 2006 and December 31st, 2015. Using a time-series design and distributed lag non-linear models (DLNM), we estimated the relative risk (RR) of ABAD presentation associated with mean daily temperatures, including cumulative RR for a 28-day period, and RR for individual daily lags through 28 days.


RESULTS
A total of 213 patients were admitted with ABAD. A significant association was found between the daily maximal temperature and the number of hospital admissions for ABAD. The lower the maximal temperature, the higher the incidence of ABAD (P = 0.044). Furthermore, the onset of ABAD was higher in winter than in summer and autumn (P = 0.009 and P = 0.001). Based on a time-series analysis, this study showed that the associations between mean daily temperature and ABAD presentation were not monotonic. Compared to the centered temperature at 8°C, the cumulative 28-day (lag 0 to lag 27) RR was significantly elevated at - 20 °C and - 19 °C for ABAD (RR = 1.39; 95%CI: 1.02, 1.98 and RR = 1.36; 95%CI: 1.02, 1.98). At the extreme low temperature (- 17.7 °C) in Shenyang, the cumulative 14-day (lag 0 to 13 day) and 21-day (lag 0 to 20 day) RR were remarkably increased for ABAD (RRlag14-day = 1.34; 95%CI: 1.08, 1.40 and RRlag21-day = 1.06; 95%CI: 1.06, 1.23). For the extreme high temperature, however, no particular finding was detected regarding acute and prolonged effects on ABAD.


CONCLUSIONS
In general, low ambient temperature was significantly associated with ABAD presentations in comparison with high temperature. The effects of cold were delayed by two weeks and persisted for a few days.