Shift work and cognitive aging: a longitudinal study

Abstract

OBJECTIVES: The few studies of shift work and late life cognitive functioning have yielded mixed findings. The aim of the present study is to estimate the association between shift-work experience and change in cognitive performance before and after retirement age among older adults who were gainfully employed. METHODS: Five hundred and ninety five participants with no dementia were followed up for a mean of 17.6 standard deviation (SD) 8.8 years from a Swedish population-based sample. Participants had self-reported information on any type of shift-work experience (ever/never) in 1984 and measures of cognitive performance (verbal, spatial, memory, processing speed, and general cognitive ability) from up to 9 waves of cognitive assessments during 1986–2012. Night work history (ever/never) from 1998–2002 was available from a subsample (N=320). Early adult cognitive test scores were available for 77 men. RESULTS: In latent growth curve modeling, there were no main effects of "any-type" or night shift work on the mean scores or rate of change in any of the cognitive domains. An interaction effect between any-type shift work and education on cognitive performance at retirement was noted. Lower-educated shift workers performed better on cognitive tests than lower-educated day workers at retirement. Sensitivity analyses, however, indicated that the interactions appeared to be driven by selection effects. Lower-educated day workers demonstrated poorer cognitive ability in early adulthood than lower-educated shift workers, who may have selected jobs entailing higher cognitive demand. CONCLUSION: There was no difference in late-life cognitive aging between individuals with a history of working shifts compared to those who had typical day work schedules during midlife.

Keywords

• longitudinal study
• aging
• retirement
• shift work
• shift worker
• cognitive performance
• ageing
• cognitive functioning
• night shift work
• growth curve modeling