Doctors commonly view excessive daytime sleepiness as a cardinal sign of disturbed or inadequate sleep. But a new study suggests it could also signal depression or even diabetes, regardless of whether an individual doesn't sleep well.

Among a random sample of 16,500 men and women ranging in age from 20 to 100 years old from central Pennsylvania, 8.7 percent had excessive daytime sleepiness.

Researchers, who considered a wide range of possible reasons for why these individuals were excessively sleepy during the daytime, found that excessive daytime sleepiness was more strongly associated with depression and obesity or metabolic factors than with sleep-disordered breathing or sleep disruption.

Depression was by far the most significant risk factor for excessive daytime sleepiness, they report in the Journal of Clinical Endocrinology and Metabolism.

The likelihood of being excessively sleepy during the daytime was more than three times higher in those who reported they were being treated for depression.

The investigators also observed strong ties between excessive daytime sleepiness and diabetes. Individuals reporting treatment for diabetes were close to two times more likely to report excessive daytime sleepiness than those who were not being treated for diabetes.

Being overweight also increased the likelihood of excessive daytime sleepiness.

Excessive daytime sleepiness was more common in people younger than age 30, a finding that hints at the presence of unmet sleep needs and depression, and in the over-75 crowd, suggesting increasing medical illness and health problems, they explain.

Smoking also emerged as a risk factor for excessive daytime sleepiness, a link that hasn't been shown before. It could be that smokers use the stimulant effect of nicotine to self-treat their daytime drowsiness, the authors suggest.

Sleep apnea -- brief episodes when breathing stops during sleep -- was not a significant player in excessive daytime sleepiness. This is consistent with prior studies that have reported only weak associations between sleep apnea and excessive daytime sleepiness.

The authors conclude that adults plagued by excessive daytime sleepiness should be thoroughly evaluated for depression and diabetes, regardless of whether or not sleep-disordered breathing is present.

医生们通常认为白天极度嗜睡是夜晚睡眠时间不足或睡眠紊乱造成的。但美国一项最新的研究结果则显示，白天极度嗜睡可能是出现糖尿病或抑郁症的征兆。

据路透社9月5日报道，美国研究人员在宾夕法尼亚州中部地区随机调查了1.65万名年龄在20岁至100岁的男女，其中8.7％的被调查者曾有过日间极度嗜睡的情况。

研究人员在考虑到很多能引起人们日间极度嗜睡的原因后发现，与睡眠呼吸紊乱或睡眠中断相比，日间极度嗜睡和抑郁症、肥胖或新陈代谢等因素具有更为紧密的联系。

研究人员发现，到目前为止，精神抑郁是导致人们日间极度嗜睡最为重要的危险因素。在那些患有抑郁症的被调查者中，出现日间极度嗜睡的可能性要比其他人高3倍还多。另外，糖尿病也和日间极度嗜睡具有非常紧密的联系。在那些患有糖尿病的被调查者中，他们出现日间极度嗜睡的可能性是其他人的近2倍。研究人员还发现，体型肥胖也能增加人们出现日间极度嗜睡的可能性。

研究人员同时发现，日间极度嗜睡症状在30岁以下的年轻人和75岁以上的老年人中更为常见。研究人员对此解释说，年轻人出现这种症状暗示着他们常常睡眠不足或精神抑郁；而老年人则是由于逐渐增多的各种疾病和健康问题所致。

值得一提的是，睡眠呼吸暂停症在日间极度嗜睡中扮演的角色却并不那么重要。这与先前一个研究结果相一致，该研究认为，睡眠呼吸暂停症和日间极度嗜睡两者之间具有的联系非常微弱。

另外，研究人员还首次发现日间极度嗜睡和吸烟之间存在着某种联系。研究人员称，一些吸烟者就是利用尼古丁的刺激作用来驱散自己在白天的睡意。