Impact of Ambient Temperature on Incidence of Acute Lower Limb Ischemia

Abstract

This was a retrospective study to explore the possible association between atmospheric temperatures with the occurrence of acute leg ischemia (ALI). A linear regression analysis was performed for a period of 10 years on the impact of ambient temperature on the incidence of ALI. Mean ambient temperature on a daily basis was retrieved electronically from our observatory, and the daily incidence of ALI was retrieved from the Clinical Data Analysis and Reporting (CDAR) system. CDAR system could retrieve clinical data from all 42 public hospitals in our region, which provided almost 90% inpatient care of the population. Daily incidence was defined as total number of emergency admissions from all 42 pubic hospitals due to ALI from 00:00 till 23:59hr of that day. For the 10-year period, spanning from January 2005 to December 2014, there were a total of 634 recorded ALI with revascularization, 608 (95.9%) of which underwent emergency femoral embolectomy, 15 (2.4%) underwent thrombolysis, and 11 (1.7%) underwent thrombolysis and embolectomy. ALIs with primary amputation or conservative management were excluded from the study. The average daily incidence of ALI was 0.170. A linear regression model was built using mean ambient temperature as independent variable and incidence of ALI as dependent variables. The line of best fit was drawn through the data points. The daily incidence of ALI could be predicted by ambient temperature (in °C) with the equation: incidence=0.274-0.004 × temperature (linear regression; r=-0.053, r2=0.003, F=10.42, and P=0.001). In other words, daily incidence was 0.274 at 0°C; and for every 10°C increase, the incidence would drop by 0.040. At 30°C, daily incidence of ALI was 0.154. This study showed an association of cold temperature and ALI in our population. Measures to protect the susceptible population from cold temperatures should be considered.