Elevated sleepiness and depressive symptoms are both viewed as risk factors for work-related accidents and injury, yet little is known about these risk factors in agriculture in general, and among farmworkers in particular. Especially important is previous research of a possible reciprocal association between elevated sleepiness and depressive symptoms. Understanding the relative dependence of these occupational risk factors has implications for health care delivery (appropriate identification and treatment of pathology; see13 and30
), as well as for creating and targeting occupational health interventions. The goal of this paper was to develop a better understanding of the interrelationship among depressive symptoms and daytime sleepiness among immigrant Latino farmworkers.
The results of this study provide one of the first descriptions of sleepiness in the Latino population. Very little sleep-related research has been done with immigrant Latino samples despite the substantial growth in the immigrant Latino population.18
Sleep research with Latino samples is especially important given the connection between sleep and occupational health outcomes,2;3
and the fact immigrant Latinos are over-represented in the most dangerous occupational sectors including agriculture.31
Our results suggest that 20% of immigrant Latino farmworkers reported elevated sleepiness at some point during the agricultural season that could place them at risk for injury. The only comparative data that could be located was a prevalence of 15.5% reported by Baron et al.,32
using data from older Latinos (M=65.7 years) in the Multi Ethnic Study of Athlerosclerosis. This single point of comparison suggests that sleepiness may be elevated among Latino farmworkers. Possible elevated sleepiness among farmworkers could be the consequence of the temporal structure of farmwork; that is, the absolute number of work hours and inadequate time for physical recovery and rest, and the timing of those work hours such as when work activities are shifted to the morning and evening/twilight hours to accommodate summer heat or particular crop needs. Both of these have the potential to contribute to disrupted sleep and subsequent daytime sleepiness, and therefore warrant attention in occupational health research and intervention.
The description of elevated depressive symptoms and sleepiness among Latino farmworkers is also a contribution to the literature. Although there is a growing literature on Latino mental health,9
this is the first study to document elevated depressive symptoms among farmworkers living in barracks. Perhaps the relative crowding in these dormitory style dwellings, or the close living quarters with relatively unknown individuals contributes to poorer mental health compared to those in other types of dwellings that are shared with more well-known individuals. This is an important area for future research. Elevated sleepiness was more common among women than men, and potentially among those who did not have a temporary work (H2A) visa. The observed gender difference in sleepiness is consistent with observations that women report higher feelings of sleepiness whereas men report more sleepy behavior.30
The differential rate of elevated sleepiness by work visa status may be attributed to generally poorer housing conditions in non-H2a camps,33
which may compromise workers’ ability to obtain restorative sleep.
The prevalence of co-occurring elevated sleepiness and significant depressive symptoms was relatively infrequent. Our estimates suggest that 3 to 5% of Latino farmworkers experienced both elevated sleepiness (i.e., ESS score ≥ 10) and elevated depressive symptoms (i.e., CES-D score ≥ 10). It is unclear whether co-occurring excessive sleepiness and depressive symptoms is elevated in our sample because good comparative data are not available. Nevertheless, the rate of co-occurrence is non-negligible; and it requires further research to determine its personal and occupational health-related implications.
The most meaningful contribution of the study is evidence indicating the absence of an iterative reciprocal association between depressive symptoms and sleepiness. Results from the lagged analyses yielded no evidence that depressive symptoms predicted subsequent sleepiness or that sleepiness preceded depressive symptoms suggesting no causal relationship between sleepiness and depressive symptoms among Latino farmworkers. These results are inconsistent with previous research suggesting that sleepiness contributes to major depression over time,15
and that unmanaged or poorly managed depression could produce subsequent experiences of sleepiness.13
However, our results are entirely consistent with the broader literature indicating a robust correlation between sleepiness and depression.34
Our results add to this literature by documenting the contemporaneous association of sleepiness and depressive symptoms in a sample of immigrant Latinos, a population with limited sleep-related research.18
The absence of a temporal association between depressive symptoms and sleepiness is informative. Theoretically, the fact that earlier depression is unrelated to subsequent sleepiness and vice versa suggests that depression and sleepiness and not causally related to each other, at least in the short term. Rather, the observed robust intercorrelation is likely due to other causes. Chellappa and colleagues 12
suggest that disruptions to circadian and homeostatic processes involving basic neurochemistry may account for the interrelationship of depression and sleepiness. This possibility is compelling because it is consistent with our results indicating that rates of elevated depressive symptoms and excessive sleepiness are greatest at the beginning of the agricultural season; the period following migration when circadian and homeostatic processes are most likely to be disrupted from physical relocation and accompanying changes in a myriad of circumstances ranging for daily work habits and routines, to changes in eating behavior and climate, to changes in housing or sleeping accommodation and social connections. This is a fertile area for research, and farmworkers provide an excellent model for studying these processes.
The significant bivariate association of sleepiness in June with depressive symptoms in August (see ) is noteworthy. The association is noteworthy because it is statistically robust despite the small sample size, and because it is consistent with evidence from previous research suggesting that sleepiness may accentuate negative emotions16
and potentially contribute to major depressive disorder.15
Although this single association should not be over-interpreted, it is compelling because the absence of a sleepiness-depression association from one month the next (evidenced in both bivariate and multivariate analyses) suggests a potential protracted latency between sleepiness, presumably caused by disrupted sleep, and the onset of elevated depressive symptoms. This protracted latency is consistent with Walker’s and Van der Helm’s16
suggestion that disordered sleep and subsequent sleepiness alters basic neurochemistry making individuals more likely to interpret environmental stimuli negatively. When combined with evidence that stressors like the pace of work escalate in the later portion of the agricultural season (i.e., August-September),9
the bivariate association hints at the possibility of a potential causal association that is worthy of more deliberate study.
The results of this study need to be considered in light of its limitations. The generalizability of the study findings is unclear, both because the sample was not designed to represent any particular group of immigrant Latino farmworkers, but also because the context of agricultural work is different in the Southeast relative to other regions of the country.36
Another limitation is the fact that this study did not explore factors like stress exposure, alcohol use or anxiety that could assist in interpreting levels of sleepiness in this sample and the possible intercorrelation of sleepiness with depression. Third, it is possible that the instruments used to assess key concepts may not be valid in immigrant Latino farmworkers. Although less concerning for the CES-D because it has undergone previous evaluation,27; 9
the Epworth Sleepiness Scale has not been fielded in this population before. As researchers respond to Loredo and colleagues’18
call for more sleep-related research among Latinos, an important first step will be determining the cross-cultural equivalence of common instruments used in sleep research. Finally, this study was unable to connect depressive symptoms and sleepiness with occupational health outcomes.
Limitations notwithstanding, this study makes several contributions. First, it marks one of the first forays into sleep research, a domain of agricultural health research highlighted by the National Research Council and the Institute of Medicine.10
Next, the results document that a substantial proportion of immigrant Latino farmworkers in eastern North Carolina may be at elevated risk for poor occupational health outcomes because of excessive sleepiness and depressive symptoms. Moreover, this elevated risk is most acute during early phases of the agricultural season and for specific groups of farmworkers (i.e., those living in barracks and potentially those without a work visa). Finally, our results help understand the interrelationship between sleepiness and depression. All of these results have the potential of improving the health of agricultural workers, either through the creation and targeting of outreach interventions if warranted by future research, or through the creation of therapeutic strategies for minimizing or treating Latino farmworkers’ experiences of elevated depressive symptoms or sleepiness.