This pilot study is one of the first to examine the impact
of job strain and shift work on both the autonomic nervous
system (ANS) and the hypothalamic-pituitary-adrenal (HPA)
axis using two salivary stress biomarkers and two subclinical
heart disease indicators. This study also tested the feasibility
of a rigorous biological sampling protocol in a busy workplace
setting. Paramedics (n = 21) self-collected five salivary samples
over 1 rest and 2 workdays. Samples were analyzed for
α-amylase and cortisol diurnal slopes and daily production.
Heart rate variability (HRV) was logged over 2 workdays with
the Polar RS800 Heart Rate monitors. Endothelial functioning
was measured using fingertip peripheral arterial tonometry.
Job strain was ascertained using a paramedic-specific survey.
The effects of job strain and shift work were examined by
comparing paramedic types (dispatchers vs. ambulance attendants)
and shift types (daytime vs. rotating day/night). Over
90% of all expected samples were collected and fell within
expected normal ranges. Workday samples were significantly
different from rest day samples. Dispatchers reported higher
job strain than ambulance paramedics and exhibited reduced
daily alpha-amylase production, elevated daily cortisol production,
and reduced endothelial function. In comparison with
daytime-only workers, rotating shift workers reported higher
job strain, exhibited flatter α-amylase and cortisol diurnal
slopes, reduced daily α-amylase production, elevated daily
cortisol production, and reduced HRV and endothelial functioning.
Despite non-statistically significant differences between
group comparisons, the consistency of the overall trend
in subjective and objective measures suggests that exposure
to work stressors may lead to dysregulation in neuroendocrine
activity and, over the long-term, to early signs of heart disease.
Results suggest that further study is warranted in this population.
Power calculations based on effect sizes in the shift
type comparison suggest a study size of n = 250 may result
in significant differences at p = 0.05. High compliance among
paramedics to complete the intensive protocol suggests this
study will be feasible in a larger population.