Why does physical pain intensify at night?

The only thing I can think of is when you wake up you are rested and your muscles are relaxed. By the end of the day you have been using and irritating the muscles and they are now inflamed again. As with the injury and a cold, perhaps you take your NASIDS and OTC medicines and again by the end of the day they wear off and symptoms are back in full swing.

I notice the same thing with the cold.

In addition to what @Cruiser suggests, it may also be that with fewer distractions at night, your mind tends to focus more on the pain.

I asked a doctor: “why do chigger bites itch horribly all night long but little during the day??” He said, “I dunno.” Big help.
I have you a GQ because I’ve wondered about this.

How about a cough? If I go out I had better take a Mucinex at bedtime or I will cough my head off all night from dust?? But cough during the daytime? I’d have to be half dead to do that.

During the day you’re busy doing things, and you don’t notice it as much.

I sure wish I knew!

Absence of distractions As my dentist was about to begin some work, I shut my eyes. He said, “Closing your eyes intensifies the experience; try opening them..” The quiet and dark of night can intensify pain.

The body’s circadian rhythm Cortisol and other stress hormones act like gatekeepers in the brain that regulate which pain signals will get through to the pain processing centers. When the levels are low, more pain signal get through; when the levels are high, you feel much less pain. Stress hormones ebb and flow throughout the day, and levels are low at night.

Dr. Vicki!

I don’t think this is a reliable generality. I have a set of pains that plague me at night and another set that comes on when I get up. It probably depends on where the pain is, what causes it, and whether it’s relieved by activity or by rest.

Physical pain caused by “arthur” etc. strikes me at any given time during the day.

But, when I have a cold, virus infection , etc. my worse time is in the evening. Also, when I had surgery on my hip, my worse time was in the evening.

I hurt worse in the evening, from fibro and such.
I toss and turn like a rotisserie chicken.

It could be the temperature. I usually feel better when I am warm.

Less input from the other senses may be allowing the pain a greater amount of your attention.