不过仅读文摘便可以估计到这个实验的大致方法，这种回顾性统计研究得出的结论用证据分类打分都不高，可以说十项回顾性研究都不如一项随机对照试验更令人信服
ZT:
Cold temperature and low humidity are associated with increased occurrence of respiratory tract infections☆
Tiina M. MäkinenabCorresponding Author Informationemail address, Raija Juvonenbc, Jari Jokelainenad, Terttu H. Harjue, Ari Peitsob, Aini Bloiguf, Sylvi Silvennoinen-Kassineng, Maija Leinonenf, Juhani Hassiah
Received 2 July 2008; accepted 16 September 2008. published online 03 November 2008.
Corrected Proof
Summary
Objective
The association between cold exposure and acute respiratory tract infections (RTIs) has remained unclear. The study examined whether the development of RTIs is potentiated by cold exposure and lowered humidity in a northern population.
Methods
A population study where diagnosed RTI episodes, outdoor temperature and humidity among conscripts (n=892) were analysed.
Results
Altogether 643 RTI episodes were diagnosed during the follow-up period. Five hundred and ninety-five episodes were upper (URTI) and 87 lower (LRTI) RTIs. The mean average daily temperature preceding any RTIs was −3.7±10.6; for URTI and LRTI they were −4.1±10.6°C and −1.1±10.0°C, respectively. Temperature was associated with common cold (p=0.017), pharyngitis (p=0.011) and LRTI (p=0.048). Absolute humidity was associated with URTI (p<0.001). A 1°C decrease in temperature increased the estimated risk for URTI by 4.3% (p<0.0001), for common cold by 2.1% (p=0.004), for pharyngitis by 2.8% (p=0.019) and for LRTI by 2.1% (p=0.039). A decrease of 1g/m−3 in absolute humidity increased the estimated risk for URTI by 10.0% (p<0.001) and for pharyngitis by 10.8% (p=0.023). The average outdoor temperature decreased during the preceding three days of the onset of any RTIs, URTI, LRTI or common cold. The temperature for the preceding 14 days also showed a linear decrease for any RTI, URTI or common cold. Absolute humidity decreased linearly during the preceding three days before the onset of common cold, and during the preceding 14 days for all RTIs, common cold and LRTI.
Conclusions
Cold temperature and low humidity were associated with increased occurrence of RTIs, and a decrease in temperature and humidity preceded the onset of the infections.
"结论：冷温度和低湿度与呼吸道感染发病率的增加相关，感染发作之前都有温度和湿度的降低。"