(cns) | While a restful night’s sleep is tougher to achieve as we get older, age has little to do with it.

“If you look at older healthy adults, they have no complaints,” said Dr. Barbara Parry, associate professor of psychiatry at U.C. San Diego's School of Medicine.

Still, almost 40 percent of people 60 or older have trouble sleeping. The reason in most cases is ill health.

“As we get older, we develop medical problems, whether it’s heart disease, neurological or arthritis,” said Sonia Ancoli-Israel, a professor of psychiatry at UCSD. Any medical or psychiatric illness can cause sleeping difficulty, she said.

And if illnesses don’t keep us awake at night, the medications we take for them often will, she said.

Then there is the duration of sleep itself. Sleep comes in four stages, the deepest being the last stage. The problem is that the final stage begins to diminish in our 20s. By the time we reach our 50s, “noise that may not have bothered us when we were younger now disturbs us,” Ancoli-Israel said.

Obesity also can contribute to insomnia. Sleep apnea, a condition in which breathing is stopped temporarily while a person is sleeping, is directly related to being overweight.

Cramps and muscle spasms also get worse as one ages. And there is plain old stress.

There is also evidence that too much sleep actually can be detrimental.

“People who had more than nine hours had an increase in early mortality and a shorter life span,” said Parry.