- Shi H et al. Rotating Night Shift Work and Healthy Aging After 24 Years of Follow-up in the Nurses' Health Study. JAMA Netw Open. 2022;5(5):e2210450. doi:10.1001/jamanetworkopen.2022.10450
The Nurses' Health Study (DOI: 10.1001/jamanetworkopen.2022.10450) was launched in 1976. 121,701 US nurses aged between 30 and 55 took part at the time. The starting point for the current study was 1988, when the nurses completed a questionnaire about their work and their experiences of night shifts. The 46,000 participants included in the study, all of whom were free of serious chronic illnesses at the time, were followed for 24 years. All of them had reached the age of 70 at the end of the follow-up period in 2012.
The researchers looked into what the health of these long-serving night shift workers was like. "Healthy ageing" was defined as follows:
The duration of rotating night shift work was divided into 4 categories:
Of the 46,000 or so participants, 3,695 (8%) entered old age in good health. All the others had problems in at least one of the defined health areas. It also emerged that the probability of ageing healthily decreased with the increasing duration of night shifts. While it was 4% lower after 1-5 years, nurses who had spent 10 or more years pulling all-nighters had an overall 20% lower probability of retiring in good health.
This applied to all dimensions of healthy ageing: the probability of reaching retirement age without serious chronic illnesses was 17% lower, for stable physical and mental health 13% lower, and for good memory function 9% lower.
The researchers suspect a possible explanation is a disruption of the circadian rhythm as a result of alternating day and night shifts. This could irritate metabolic functions and favour the development of diseases. Chronic sleep deprivation could also have a negative impact on mental health and cognitive functions. And finally, unfavourable changes in health behaviour increase the risk of overweight and obesity, which in turn is an independent risk factor for healthy ageing.
Long-term night shift work not only shortens life expectancy, but also worsens the general state of health of older people and thus impairs the remaining years of retirement age. This problem is becoming even more urgent in view of an ageing population. This makes it all the more important to minimise potentially modifiable negative factors such as night shifts as far as possible.