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Usual Alcohol Consumption and Arterial Oxygen Desaturation During Sleep
To the Editor: Although acute alcohol ingestion is known to aggravate the severity of sleep-disordered breathing (SDB), no population-based epidemiologic study has been conducted to examine the effect of usual alcohol consumption.1 We investigated the association between usual alcohol consumption and nocturnal oxygen desaturation.
Methods
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Participants were recruited for a sleep study as a population-based sample from the 2000 to 2002 annual cardiovascular risk surveys of men in 3 Japanese communities. Participants were required to be 40 to 69 years old. Of the 1741 men eligible, 1517 (87%) agreed to participate.
A pulse oximeter (PULSOX-3Si, Minolta Co, Osaka, Japan) was attached to the wrist and index finger during all-night sleep at home. Every second it recorded a 5-second moving average of arterial blood oxygen saturation; thus, sampling time was short enough for accurate estimation of oxygen saturation.2 We used a sleep diary to exclude waking time from the analysis to minimize the potential overestimation of sleep duration. Data associated with total recording time less than 4 hours (n = 46) or with artifact likely due to frequent body movement, inadequate fitting of the probe, or excessive pulse pressure (n = 46) were excluded, leaving data from 1425 men available for analyses. The 3% oxygen desaturation index (ODI) was used to define SDB: 5 to less than 15 events per hour was considered mild SDB, and 15 or more events per hour was considered moderate to severe SDB. Pulse oximetry has been reported to have a sensitivity of 80% and a specificity of 95% for detecting an apnea-hypopnea index of 5 or greater using an ODI cutoff threshold of 5, and a sensitivity of 85% and a specificity of 100% using an ODI cutoff threshold of 15.3 Body mass index (BMI) was calculated as weight in kilograms divided by the square of height in meters.
Weekly ethanol consumption was based on interviews of participants. We found these values to be highly reproducible on measures 1 year apart (data not presented). To assess validity of these measures, mean levels of serum gamma-glutamyl transferase were compared according to reported ethanol consumption level after adjustment for age, BMI, smoking, and community. We also measured alcohol consumption on the night of the study.
A linear trend of current ethanol intake levels with ODI levels was tested using median values of the current ethanol intake categories. Analysis of covariance and logistic regression analysis were used to measure the mean ODI levels and the odds ratios (ORs) for the occurrence of SDB according to categories of ethanol intake per day per body weight in kilograms after adjustment for age, BMI, and smoking status (never, former smoker, currently 1-19 cigarettes/d, and currently  20 cigarettes/d). Participants were also stratified by BMI and the same analyses performed, adjusted only for age and smoking status.
The study was approved by the Medical Ethics Committee of the University of Tsukuba, and written informed consent was obtained from all participants.
Results
Study participants were slightly older (mean age, 58.4 vs 56.8 years) and less likely to be smokers (proportion of current smokers, 42% vs 52%) than nonparticipants. There was no difference in BMI or usual alcohol consumption levels between the 2 groups. Levels of serum  -glutamyl transferase among participants were 33 IU/L (never drinkers), 36 IU/L (former drinkers), 56 IU/L (ethanol consumption of <0.5 g/day per kg), 79 IU/L (ethanol consumption of 0.5 to <1.0 g/day per kg), and 97 IU/L (ethanol consumption of 1.0 g/day per kg) (P<.001 for trend).
Median ethanol consumption was 0 g/d per kg for never and former drinkers, 0.25 g/d per kg for those consuming less than 0.5 g/d per kg, 0.70 g/d per kg for those consuming 0.5 to less than 1.0 g/d per kg, and 1.14 g/d per kg for those consuming 1.0 g/d per kg or more.The mean ODI level correlated positively with ethanol intake among total participants (P = .003 for trend) (Table 1). For all participants with an ODI of 5 per hour or greater, the ORs for SDB were 1.45 (95% confidence interval [CI], 1.02-2.04) for those with ethanol intake of 0.5 to less than 1.0 g/d per kg and 1.95 (95% CI, 1.15-3.31) for those with an intake of 1.0 g/d per kg or more. For participants with an ODI of 15 per hour or greater, the ORs for SDB for these same categories were 1.94 (95% CI, 1.06-3.54) and 3.08 (95% CI, 1.30-7.29), respectively. For participants with an ODI of 5 per hour or greater and the greatest ethanol consumption, the association with SDB was stronger in those with lower BMI than in those with higher BMI (OR, 2.31; 95% CI, 1.13-4.72 vs OR, 1.13; 95% CI, 0.52-2.44, respectively). There were similar associations between alcohol consumption and mean values of oxygen desaturation (data not presented). When we analyzed alcohol consumption on the night of study, we found similar results, with a somewhat lower association for participants with an ODI of 15 or greater among men with an ethanol intake of 1.0 g/d per kg or more (OR, 2.35; 95% CI, 0.96-5.75).
Comment
We found a significant positive association between usual alcohol consumption and the severity of SDB among middle-aged Japanese men, independent of age, BMI, and smoking. There was an association with SDB even among men with a moderate ethanol intake (0.5 to <1.0 g/d per kg). We believe that the smaller effect found with alcohol consumption measured on the night of the study may represent usually heavy drinkers modifying or underreporting their alcohol consumption at that particular time. The overall findings are concordant with the results of an experimental study demonstrating an increase in the mean apnea-hypopnea index from 7.1 to 9.7 per hour following ingestion of ethanol prior to sleep at a dose of 0.5 g/kg.4 Alcohol depresses hypoglossal muscle activity and waking ventilatory responses to asphyxia. The association between alcohol intake and SDB among men with higher BMI may have been masked by a strong effect of excess weight on SDB. The stronger association between alcohol intake and SDB among nonoverweight patients with SDB emphasizes the importance of alcohol abstinence in this group.
Funding/Support: This study was supported in part by the Japanese Ministry of Education, Culture, Sports, Science and Technology (grant-in-aid for research B: 14370132), the Health and Labour Sciences Research Grant (Clinical Research for Evidence Based Medicine), Ministry of Health, Welfare and Labour, Japan, and a research grant from FULHAP, Japan.
Role of the Sponsors: The organizations funding this study had no role in the design and conduct of the study; the collection, interpretation, and analysis of the data; the preparation of the data; or the preparation, review, or approval of the manuscript.
Acknowledgment: We are grateful to Mss Minako Kudo and Yukiko Ichikawa for their technical assistance.
Takeshi Tanigawa, MD
Tt9178{at}aol.com
Department of Public Health Medicine
Graduate School of Comprehensive Human Sciences
University of Tsukuba
Ibaraki, Japan
Naoko Tachibana, MD
Osaka Medical Center for Health Science and Promotion
Osaka, Japan
Kazumasa Yamagishi, MD;
Isao Muraki;
Mitsumasa Umesawa, MD
Department of Public Health Medicine
Graduate School of Comprehensive Human Sciences
University of Tsukuba
Takashi Shimamoto, MD
Osaka Medical Center for Health Science and Promotion
Hiroyasu Iso, MD
Department of Public Health Medicine
Graduate School of Comprehensive Human Sciences
University of Tsukuba
1. Young T, Peppard PE, Gottlieb DJ. Epidemiology of obstructive sleep apnea: a population health perspective. Am J Respir Crit Care Med. 2002;165:1217-1239.
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2. Clark JS, Votteri B, Ariagno RL, et al. Noninvasive assessment of blood gases. Am Rev Respir Dis. 1992;145:220-232.
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3. Nakamata M, Kubota Y, Sakai K, et al. The limitation of screening tests for patients with sleep apnea syndrome using pulse oximetry [in Japanese with English abstract]. J Jpn Soc Respir Care. 2003;12:401-406.
4. Scanlan MF, Roebuck T, Little PJ, Redman JR, Naughton MT. Effect of moderate alcohol upon obstructive sleep apnoea. Eur Respir J. 2000;16:909-913.
ABSTRACT
Letters Section Editor: Robert M. Golub, MD, Senior Editor.
JAMA. 2004;292:923-925.
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