NEW YORK (Reuters Health) - Norwegian and Swedish users of mobile phones commonly report headaches, warmth on the ear and burning sensations of the facial skin, according to a report published in a recent issue of the journal Occupational Medicine.

Dr. Gunnhild Oftedal, of the Norwegian University of Science and Technology in Trondheim, and colleagues in Sweden sent a questionnaire to 12,000 people in Sweden and 5,000 in Norway who use mobile phones as part of their job. In Sweden, 7,803 people responded, and in Norway there were 2,828 respondents.

Among the Norwegians, 31% experienced at least one symptom, while among the Swedish respondents, 13% reported one or more symptoms associated with mobile phone use. The researchers account for this difference by noting differences in the response rate and population characteristics between the two groups. They also point out that the reported symptoms were similar for both groups.

``The warmth sensations were predominately experienced during the mobile phone call. Other symptoms, like headaches, most often began during or within half an hour after the call and usually lasted for up to 2 hours,' according to the report.

Among the Norwegians, the investigators found that, depending on the symptom, 48% to 78% ``indicated that the phone call had to be 5 minutes or longer to provoke the symptoms.' Similarly, 38% to 68% of the Swedish participants reported that symptoms developed after 5 minutes or longer. Other factors related to symptom onset for subjects in both countries were stress conditions (16%) and difficulty hearing (10%).

Most of the respondents had not seen a physician, but about 45% had taken steps to relieve their symptoms. The most common strategies for symptom relief, according to the researchers, were reducing the duration of calls and using ``hands free equipment.' They add that ``most people experienced a reduction of the symptom as a result of the reported steps.'

``The fact that people experience a symptom, or become aware of a symptom during or shortly after a phone call, does not necessarily imply a causal relation between the use of the mobile phone and the symptom,' Oftedal and colleagues caution. They also add that the study findings ``can not be generalized to all mobile phone users.'

难点词汇：
　　 Norwegian　 挪威的，挪威人　 　 　Swedish　瑞典人，瑞典的　　　sensation　感觉
　　 questionnaire　调查问卷　　　 　　symptom　症状　　　　　　　　respondent　 回答者
　　 predominately　主要地，优势地　 　provoke　惹起, 驱使　　　　　onset　发作
　　 caution　 警告 　　　　　　　　　 generalize　归纳，推广