Impact of ambient temperature and atmospheric evaporation on the incidence of acute deep venous thrombosis in the northeast of China.

BACKGROUND

Meteorological variables have been reported to be associated with increased morbidity; however, fewer studies have study the correlations between the occurrences of acute deep venous thrombosis (DVT) and meteorological variables.

METHODS

Data relating to hospital admissions with DVT in Shenyang were collected retrospectively for a ten year period for which corresponding meteorological recordings were available. Using a time-series design and distributed lag nonlinear models (DLNM), we estimated the relative risk (RR) of DVT presentation associated with mean daily temperatures, including cumulative RR for a 28-day period, and RR for individual daily lags through 28 days.

RESULTS

We found significant seasonal variation in DVT with a winter peak. A significant correlation was found between the ambient temperature and the number of hospital admissions for DVT. The lower the average, minimal, and maximal ambient temperature, the higher the incidence of DVT (P=0.001, P=0.002, and P<0.001). Furthermore, high evaporation (P=0.026) and high vapor pressure (P=0.003) on the date of admission was associated with an increase in the rate of presenting with DVT. Based on a time-series analysis, this study showed that the associations between mean daily temperature and DVT presentation were not monotonic. Compared to centered temperature at 8 °C, the cumulative 28-day (lag 0 to lag 27) RR was significantly elevated at -16 °C, -15 °C, -14 °C, and -13°C for DVT (P<0.05). To the extreme low temperature (-17.7 °C) in Shenyang, the RR of cumulative 8-day (lag 0 to 7 days) was remarkably increased for DVT (RRlag8-day=1.03, 95% CI: 1.01-1.05). For the extreme high temperature, nevertheless, no particular finding was detected regarding acute and prolonged effects for DVT.

CONCLUSIONS

In general, low ambient temperature was significantly associated with DVT presentations in comparison with that of high temperature. The effects of cold were delayed by one week. DVT is particularly associated with high evaporation and high vapor pressure.