Effects of Sleep Deprivation on Fire Fighters and EMS ... - NAEMT

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<strong>Effects</strong> <strong>of</strong> <strong>Sleep</strong> <strong>Deprivation</strong> on Fire Fighters and Other EMS Responders Long work hours and sleep deprivation may result in performance-related slowed reaction times and less alertness. They also can lead to a constant feeling <strong>of</strong> fatigue, irritability and a reduced sense <strong>of</strong> well being. 1.5 Physiological <strong>Effects</strong> In general, long work hours and chronic sleep loss have been associated with adverse health consequences for most bodily systems (Knutsson, 2003; Sparks et al., 1997; Spurgeon, Harrington & Cooper. 1997; van der Hulst, 2003). Table 1.3 (page 14) summarizes studies assessing work hours and general health/overall mortality, and a consistent relationship between increasing work hours and more health complaints was observed across studies. More recent data from approximately 20,000 European workers from a broad range <strong>of</strong> occupations confirmed a clear direct correlation between the number <strong>of</strong> hours worked per week and health complaints (Raediker et al., 2006). Caruso and colleagues (2004) performed a critical review <strong>of</strong> studies linking work hours and health outcomes. In their analysis, they separated shift work in general and shift work that involved more than 40 hours <strong>of</strong> work a week. When those latter criteria were met, findings consistently demonstrated lower perceived general well being and more health problems, along with an increased risk <strong>of</strong> occupational injuries. Eight hours <strong>of</strong> sleep per night is recommended for adults, because that number is the average preferred duration among healthy adults, who do not have other demands limiting sleep. Longitudinal mortality studies and sleep seem to confirm that optimum duration. Mortality increases in men and women when they deviate from that amount. In long term studies, even controlling for other factors influencing life expectancy, sleeping less than that per night was associated with higher mortality (Heslop et al., 2002; Patelet et al., 2004). 1.5a Cardiovascular Disease The evidence linking long working hours and adverse cardiovascular events is not yet definitive, but findings are concerning. Several lines <strong>of</strong> evidence indicate that long work hours (more than 50 to 60 hours each week) increase the incidence <strong>of</strong>, and risk factors for, heart disease and cardiovascular events. The potential mechanisms for this association include Comparisons are difficult, but some have suggested getting less than six hours <strong>of</strong> sleep per night increases heart disease risk comparable to that <strong>of</strong> smoking a pack <strong>of</strong> cigarettes a day (Akerstdt et al., 1984). lack <strong>of</strong> normal cardiovascular rest during deep sleep, increased inflammation associated with sleep deprivation (see Section 1.5d) and the unhealthy lifestyles that accompany long work hours. In a study <strong>of</strong> individuals admitted to U.S. hospital with myocardial infarction, more than half regularly worked more than 60 hours per week, compared with only one-quarter <strong>of</strong> a matched control group (Thiel, Parker & Bruce, 1973). As shown in Table 1.4, other studies have found a direct relationship between the risk <strong>of</strong> myocardial infarction and longer working hours, with a two-fold increase in risk associated with working more than 40 hours each week (Sokejima & Kagamimori, 1998; Lui et al., 2002). Most studies linking heart disease and long work hours have been among Japanese men. However, recent longitudinal assessment <strong>of</strong> U.S. nurses has confirmed that short sleep duration, even after adjusting for other risk factors, increased the risk <strong>of</strong> coronary heart disease by 50 percent, and interestingly, long sleep duration (more than 9 hours a night) also increased that risk (Ayas at al., 2003). 9
<strong>Effects</strong> <strong>of</strong> <strong>Sleep</strong> <strong>Deprivation</strong> on Fire Fighters and Other EMS Responders The stages <strong>of</strong> deep sleep are times when the heart rate and blood pressure are lowered, and important bodily repair functions may occur. Disruption in that sequence may predispose to hypertension. Daytime ambulatory blood pressure cuff measurements found that prolonged work hours were associated with an increase in blood pressure (Fialho et al., 2006). Large cross-sectional studies also support the relationship between loss <strong>of</strong> sleep and hypertension (Gangwisch et al., 2006). Along with high blood pressure, tobacco use is a major risk factor for heart disease, and lack <strong>of</strong> sleep has been associated with greater tobacco use (Caruso et al., 2004). 1.5b Digestive Disorders Digestive enzymes are secreted in a cyclical fashion related to the normal daily rhythm, and the different daily patterns and unusual meal times <strong>of</strong> longer work hours and night shifts may disrupt that normal sleep physiology. Those alterations may relate to the up to six-fold increase in gastrointestinal disorders, such as peptic ulcers, indigestion, diarrhea and constipation, observed among those with sleep deprivation and night shift work (Reid et al., 1997; Orr & Chen, 2005). 1.5c Obesity, Diabetes and Obstructive <strong>Sleep</strong> Apnea Strong mounting evidence links sleep loss with obesity and the hormonal changes that result in weight gain (Vorona, Winn & Babineau, 2005). Over the last 40 years, self-reported sleep duration in the U.S. has decreased by almost two hours, and that change coincides with a marked increase in the prevalence <strong>of</strong> obesity. Large longitudinal studies <strong>of</strong> the U.S. population have found that young adults (ages 30 to 50 years old) with sleep durations at <strong>of</strong> less than seven hours per night were more likely to gain weight and become obese than subjects with longer sleep durations (Gangwisch et al., 2005). Six large U.S. studies and investigations from six other countries have linked lack <strong>of</strong> sleep with obesity (Cizzi, Skarulis & Mignot, 2005). Weight gain and obesity have strong genetic components, comparable to the inheritance <strong>of</strong> height. In recent years, researchers have recognized that obesity is a metabolic disorder, and they have identified the physiology explaining why people differ in their propensity to gain weight. In part, those are explained by differences in the hormone levels that regulate eating behavior and metabolic rate. Ghrelin is a hormone produced by stomach cells that stimulates the appetite, and its level increases before meals. It is considered the counterpart <strong>of</strong> the hormone leptin, produced by adipose tissue. Leptin levels directly relate to the amount <strong>of</strong> body fat, and higher levels lead to reduced eating and an increase in metabolic rate. Higher ghrelin levels stimulate appetite, as do lower levels <strong>of</strong> leptin. Laboratory studies and observations in the field indicate that shorter sleep duration in young, healthy adults is associated with a hormonal pattern (decreased leptin and increased ghrelin levels) that stimulates hunger and promotes weight gain (Spiegel et al., 2004; Copinschi, 2005). Weight gain and obesity are associated with development <strong>of</strong> type 2 diabetes (Speigel et al., 2005). Short sleep durations more than double the risk <strong>of</strong> developing diabetes (Yaggi, Araujo & McKinlay, 2006). A longitudinal study <strong>of</strong> Japanese workers documented that those not on day shifts had a significantly greater risk <strong>of</strong> developing diabetes over 10 years, even when controlling for body weight, One <strong>of</strong> the strongest biological links is between chronic sleep deprivation and weight gain. 10
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