Night work is necessary in hospitals, factories and many services.
Medical researchers classify it as a probable .
The harm comes from of the body clock rather than from the workplace itself.
Sleep in the day is shorter and lighter, and the accumulates across a week.
Accident rates on night shifts are consistently higher, with a peak between three and five in the morning.
Some of this cannot be avoided, and a great deal depends on how the is built.
Rotating forward, from morning to afternoon to night, is tolerated far better than rotating backward.
Two nights are easier to recover from than five.
Short rest periods between shifts are the single most damaging design, and the most common.
Workers frequently prefer the , since it produces longer breaks.
Their preference is real and does not make the schedule safe.
Regulation therefore sets minimum rest rather than maximum hours in most countries.
for night work is common, and paying for harm is not the same as reducing it.