Objective: This study focuses on evaluating the relationship between physical findings, particularly collar size and Body Mass Index (BMI), and polysomnographic parameters in male patients seen at a Sleep Disorders Laboratory, suspected to have Obstructive Sleep Apnea (OSA). Methods: Design: Cross-sectional study Setting: Academic tertiary private hospital Participants: Charts of 149 adult male patients referred for polysomnography between July 1, 2005 and June 30, 2006 were reviewed. Height,

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... ight, and external neck circumference measurements were obtained. The data from polysomnography results were noted and correlated with the physical measurements. Results: The mean collar size for the OSA group was 42.03 cm with a mean BMI of 29.14 while the mean collar size for the normal group was 39.05 cm with a mean BMI of 25.36. A significant difference was noted in both the collar size and body mass index (BMI) between the OSA group and the normal group (p<0.005). Results showed a significant correlation between collar size and BMI. Collar size and BMI measurements were also correlated with increasing severity of sleep apnea in the OSA group. The ³40 cm collar size among male adults with symptoms of OSA was 80% sensitive and 67% specific with a positive predictive value of 94% in predicting true OSA. Conclusion: This study suggests that the external neck circumference and the degree of obesity determined through BMI measurement may be important predictors of sleep apnea in adult Filipino males suspected to have OSA. Given the high probability of having true OSA in symptomatic male adults with a collar size ³ 40 cm, outright definitive management may be opted for in these patients, while those with a collar size < 40 cm may need to undergo further confirmatory tests. Keywords: obstructive sleep apnea, external neck circumference, collar size, body mass index, polysomnography, obesity