Mental problems causing sleep disturbance are three times more common in younger adults. The commonest psychiatric problem in the elderly is very treatable depression. Sleep apnea is repeated 10 second periods of stopping breathing. Continuous nocturnal positive pressure through the nose can treat this. Others need minor surgical nasal passage correction.
Restless legs is a strong urge before sleep to repeatedly move ones legs preventing sleep.
If severe it can be treated with levodopa, opioids, or benzodiazepines. Sleeping pills may stop working after two weeks and it can take several weeks to recover from their effects. They can also exacerbate sleep apnea. If you are on pills, reduce the dose by a quarter weekly. Exercise works better than pills.