In comparing the results across studies, the writers of the meta-analysis found that on the whole, music caused significant improvements in sleep quality.[iii] The only exceptions to this occurred in two trials where researchers studied people with chronic sleep disorders for less than three weeks; in these cases, sleep quality did not significantly improve when people listened to music.[iv] However, in four of the ten studies the benefits of listening to music seemed to accumulate over time.[v] Considering this, you have to wonder if music might have significantly improved sleep quality in all of the studies if researchers had looked at its effects over a longer period of time. The authors of the meta-analysis obviously wondered this too, because they wrote that researchers must follow-up with study participants for more than three weeks in order to properly evaluate the effect of music on people with chronic sleep disorders.[vi]