Effect of Air Temperature and Wind Speed on the Incidence of Tuberculosis in Lanzhou

Objectives To explore the effect of air temperature and wind speed on incidence of tuberculosis and sensitive population.

Methods The data of daily reported tuberculosis cases in Lanzhou from 2008 to 2016 and the meteorological data at the same period were collected and integrated. The distributed lag nonlinear model(DLNM)was fitted to reveal the relationship between the mean air temperature and the incidence of tuberculosis cases.

Results A total of 16 996 cases were reported from 2008 to 2016, the ratio of male to female was 1.56 and most of patients (40.92%) were in the age of (36～64) years. There was a non-linear relationship between the mean air temperature and the number of tuberculosis cases. Taking the mean air temperature (11.11℃) as a reference, the exposure-response relationship between low-temperature effect and the number of tuberculosis cases was in an inverted U-shape, and the relative risks (RR) was the highest (1.14; 95% CI:1.02～1.26) while the air temperature was -9℃ with a 6 day lag time. The highest accumulative effect of low temperature (-5.2℃) was lagged for 14 days, and the RR for the male, (36～64) year-old people and the elders were 1.30(1.11～1.53), 1.30(1.10～1.55) and 1.25(1.06～1.46), respectively. The exposure-response relationship between high temperature and the daily cases of tuberculosis was in a S-shape, and the highest RR was 1.13(1.01～1.26) when the mean temperature was 28℃ with a 3 day lag time. The accumulative effect of high temperature (20.1℃) was the highest on 5 day lag time, and the RR for the male and (36～64) year-old people were 1.31(1.00～1.71) and 1.51(1.14～2.00), respectively. The association of wind speed and the risk effects of tuberculosis was roughly positive.

Conclusions Low and high temperature increased the risk of tuberculosis. The effect of low temperature lasted longer than that of high temperature. The male, (36～64) year-old people and the elders were sensitive to low temperature, and high temperature mainly affected men and young adults. High wind speed also increased the risk of tuberculosis.