Despite the belief that caffeine keeps us awake, researchers say they couldn't find any evidence that drinking coffee in the evening is the culprit. Instead, smoking and wine were more likely to cause a sleepless night.
Researchers from Florida Atlantic University tracked the lifestyle and sleeping habits of 785 people for a total of 5,164 days. In particular, they were looking at alcohol and caffeine consumption and smoking four hours before bedtime.
People who smoked or drank wine before going to bed were more likely to suffer interrupted sleep, although coffee didn't have the same effect.
Of the three, smoking had the most dramatic impact, with smokers losing around 42 minutes of sleep.
Up to 70 million Americans regularly suffer a disturbed sleep.