Q: My doctor insists that I should get more sleep, but if it feels OK to sleep for just about five hours a night, isn’t that what my body naturally needs? I am 53 and in pretty good health. — Steve R., White Plains, N.Y.

A: Sleep is a complicated phenomenon. You may feel like it’s just a passive respite from the daily grind, but your body is as active while you sleep as it is while you’re awake.

Among the various bodily functions that are affected by the lack of sufficient sleep, there’s memory consolidation, abstract thinking and cognition, neuron repair, gut biome health, and immune system strength and resilience. And that doesn’t even include what goes on in your bone-building osteoblasts and your lipid- and glucose-processing liver when you sleep — or the disruption of those processes that happens when you don’t get enough sleep.

How much is enough? Studies indicate that seven hours a night is a good target for folks in their 50s, 60s and 70s. A new study in PLOS Medicine looked at the risk of multiple serious health conditions that are associated with sleep duration. Data on more than 10,000 people covering 25 years reveals that folks in their 50s who get five or less hours of sleep a night are at a 20% greater risk of developing a chronic condition in the short term and 40% more likely to be diagnosed with two or more chronic diseases over 25 years. Sleeping less than five hours or more than nine at age 60 also bumped up the risks.

Another hazard: If you’ve been diagnosed with a chronic condition, then sleeping for nine or more hours a night increases your risk of being diagnosed with a second chronic condition by 35%.

My suggestion for you: Ask your doctor for a referral to a sleep clinic; turn off all digital devices two hours before bedtime; sleep in a dark, cool, quiet room.