Can adults adapt to less sleep?
A paper by Kaul et al. from 2010 suggest that meditation can indeed decrease the need for sleep. Meditation acutely improves psychomotor vigilance, and may decrease sleep need

Quote from conclusions:


  These results suggest that meditation provides at least a short-term performance improvement even in novice meditators. In long term meditators, multiple hours spent in meditation are associated with a significant decrease in total sleep time when compared with age and sex matched controls who did not meditate. Whether meditation can actually replace a portion of sleep or pay-off sleep debt is under further investigation.