Introduction: Cardiometabolic disorders (CMD) are highly prevalent among workers. Though much evidence
has gained that shift work is a risk factor for CMD onset among healthy workers, its
impact on CMD prognosis is under-investigated. The aim of our study was to examine
the temporal relationships between shift work and mortality outcomes among workers
with CMD, and to provide insights into targeted secondary prevention strategies for
this population.
Methods: Data was extracted from the 2010 and 2015 National Health Interview Survey (NHIS),
which employed multistage sampling techniques to select dwelling units representing
the civilian, non-institutionalized adult population (age 18 or older) of the United
States (U.S.). A total of 9,622 workers with CMD and complete data were included.
Working schedule was self-reported at baseline and shift work was defined as ‘a regular
evening shift’, ‘a regular night shift’, or ‘a rotating shift’. The National Center
for Health Statistics (NCHS) provided a linkage to the NHIS data with death records
from the National Death Index (NDI) where participants were followed up through December
31, 2019 for mortality outcomes, including all-cause mortality, CMD mortality, and
cardiovascular diseases (CVD) mortality. Cox proportional hazards models were used
to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), with adjustment
for baseline demographic information, socioeconomic status, and occupational characteristics.
Results: Among 9,622 study participants, 2,470 (25.7%) were engaged in shift work at baseline.
Over the follow-up period, 308 deaths in the non-shift work group and 129 deaths in
the shift work group were documented, resulting in the all-cause mortality rates of
45.0 per 1000 person-years and 52.2 per 1000 person-years, respectively. Furthermore,
CMD mortality rates were 14.0 per 1000 person-years (in the non-shift work group)
and 20.2 per 1000 person-years (in the shift work group), CVD mortality rates were
12.6 per 1000 person-years (in the non-shift work group) and 17.4 per 1000 person-years
(in the shift work group). After adjusting for baseline covariates, including age,
sex, race, marital status, education, income, insurance, number of jobs, and occupation,
multivariable regression analyses suggested that shift work was associated with a
28% higher risk of all-cause mortality (HR=1.28, 95% CI=1.02, 1.62), a 57% higher
risk of CMD mortality (HR=1.57, 95% CI=1.01, 2.42), and a 61% higher risk of CVD mortality
(HR=1.61, 95% CI=1.02, 2.53).
Conclusion: In this nationally representative cohort of U.S. workers with CMD, shift work contributed
to a significantly higher risk of mortality. We anticipate that our research will
address critical knowledge gaps among workers with CMD, thereby ultimately improving
current clinical guidelines for CMD secondary prevention, given the fact that the
current guidelines in the U.S. do not recognize the crucial role of workplace / working
conditions in preventing adverse outcomes among CMD patients.
