Prevalence of sleep apnea among Japanese industrial workers determined by a portable sleep monitoring system.

We developed a new portable sleep monitoring system and studied the prevalence of sleep apnea syndrome among Japanese industrial workers. This device assessed three kinds of parameters: nasal airflow, tracheal sound and electrocardiogram (ECG), and digitally stored the clock time of the onset of apnea, apnea duration and R-R intervals by a built-in microcomputer. After monitoring, the portable sleep monitor was connected to a host computer, and apneic episodes, the so-called 'apnea index' as apneic episodes corrected by measuring time ('AI') and R-R intervals were analyzed. In 170 inpatients referred to our sleep clinic, sleep monitoring by this device was performed simultaneously with all-night polysomnography, and the sensitivity and specificity of this device was determined under different criteria of the apnea index (AI) (AI > 5, 10, 15 and 20 episodes/h) by polysomnography. In all AI criteria, the sensitivity was more than 90%, and the specificity was also reasonably high. Using this system, successive 2-night home sleep monitoring was performed on 168 healthy workers in one Japanese industrial company, and 159 people (140 males; 19 females) who had successful monitoring were analyzed. The percentage of persons who had 'AI' of more than 10 episodes/h was 7.5%. There were no significant correlations between 'AI' and age, body weight or scores estimated by sleep questionnaires. These results suggest that even in people who are seemingly healthy significant apneic episodes could be detected by the portable home sleep monitoring system. This system may therefore be useful in evaluating the occurrence of sleep apnea syndrome in general populations.