Obstructive Sleep Apnea - Drivers At Risk

According to medical research, Obstructive Sleep Apnea (OSA) is a major contributing factor in vehicle crashes, resulting in thousands of deaths and injuries each year.^1,2 This represents a two- to seven-fold increase in risk over drivers not suffering from OSA.³ OSA may cause some drivers to fall asleep at the wheel or be more likely to suffer from lack of alertness due to sleep deprivation. In many instances, OSA is left undiagnosed and therefore goes untreated. Not only can OSA increase the risk of a driver being involved in a crash, but it also increases the possibility of that individual having significant health problems such as high blood pressure (hypertension), heart attacks, stroke, and mood disorders.

What Is OSA?

OSA is a serious medical condition which is characterized by pauses or gaps in the breathing due to a partial blockage or closure of the upper airway during sleep. This causes repeated sleep disturbances and possible complete awakenings. When asleep, the person’s back throat muscles relax, causing repeated stops and starts in breathing. It sometimes reduces oxygen levels and can be accompanied by loud snoring. The Mayo Clinic calls OSA a “potentially serious sleep disorder” because people stop breathing repeatedly during their sleep, often for a minute or longer and as many as hundreds of times during a single night. It leads to poor sleep quality and excessive daytime sleepiness.

Prevalence of OSA

Estimates are that nearly one in three drivers suffers from mild to severe OSA.⁴ Given the public safety risks associated with OSA, it has been suggested that mandating OSA screenings could reduce the risk of motor vehicle collisions.

The prevalence of OSA has been shown to be dependent on the relationship between two major factors — age and degree of obesity, as measured by body mass index (BMI).⁵ While age and body mass index are the two major factors, only age has been found to be associated with both OSA and the occurrence of crashes. The mean age of subjects with some degree of OSA was 48.7 years compared to an average age of 45.5 years for those who were not diagnosed with OSA.⁶ While older drivers are at higher risk, it should be noted that younger drivers with fewer years of driving experience also have an increased likelihood of motor vehicle collisions.

Another meaningful study finding showed that the prevalence of OSA depends on the average duration of sleep over consecutive nights. Short sleep duration of six hours or less per night results in an increase in the prevalence of OSA.

Most Common Symptoms of OSA

The signs and symptoms of OSA result from disruption of the normal sleep pattern. The frequent arousals and the inability to achieve or maintain the deeper stages of sleep can lead to excessive daytime sleepiness, non-restorative sleep, automobile accidents, personality changes, decreased memory, erectile dysfunction (impotence), and depression. Individuals rarely complain about frequent awakenings due to obstruction, but awakenings do occur. Excessive daytime sleepiness may be mild or severe, depending on the severity of the obstruction. In some cases, individuals continue to experience excessive daytime sleepiness while they are being treated for OSA.

Predisposing Factors

Often the person with OSA is not the first to recognize the signs. OSA is often first noticed by the bed partner or a person who observes the patient at rest. Many people who have OSA have no sleep complaints. Predisposing factors⁷ include:

• Obesity – The primary risk factor for OSA is excessive weight gain; a BMI ≥ 30 is a predictor of OSA. The accumulation of fat on the sides of the upper airway causes it to become narrow and predisposed to closure when the muscles relax.
• A thick or large neck – A neck circumference greater than 17 inches (43 centimetres) is associated with an increased risk of OSA. That’s because a thickneck may narrow the airway and may be an indication of excess weight.
• High blood pressure (hypertension) – OSA is 50% more common in people with hypertension.
• A small airway – A smaller airway in the nose, throat, or mouth. The small airway can be related to the actual size and shape of the airway, or to obstructions (such as adenoids) or other medical conditions that are causing obstructions.
• Being male – Men are twice as likely to have OSA, in fact, 4% of middle-aged men have OSA; male hormones can cause structural changes in the upper airway.
• Being older – Loss of muscle mass is a common consequence of the aging process.If muscle mass decreases in the airway, it may be replaced with fat, leaving the airway narrow and soft. People over 65 years of age have a higher risk of having OSA, especially if they also have other risk factors.
• Having heart disorders – People with atrial fibrillation or congestive heart failure are 25% more at risk of OSA.
• Family history – If an individual has family members with OSA, he/she may be at increased risk.
• Use of alcohol, sedatives, or tranquilizers – These substances relax the muscles in the throat.
• Smoking – Smokers are three times more likely to have OSA than are people who have never smoked. Smoking may increase the amount of inflammation and fluid retention in the upper airway. This risk likely drops after the smoker quits.
• Prolonged sitting – Studies suggest that long periods of daytime sitting can cause fluids to shift from the legs when a persons reclines at night. This narrows airway passages and possibly increases the risk of OSA.

Severity of OSA and Crash Risk

Most studies use the scores on the Apnea-Hypoxia Index (AHI) to measure the severity of OSA. In 18 studies that reported on this relationship, seven studies demonstrated a significant positive statistical relationship between the severity of apnea and crash risk.⁸

Apnea-Hypoxia Index⁹

• Mild OSA is associated with five or more episodes of apnea/hour; odds of having hypertension is 42% greater.
• Moderate OSA is associated with 15+ episodes of apnea/hour; doubles the risk of hypertension.
• Severe OSA is associated with 30+ episodes of apnea/hour; triples the risk of hypertension.
  

Predisposing Factors Screening Questionnaire¹⁰

• Do you use or are you supposed to use a breathing machine (Continuous Positive Airway Pressure (CPAP) or Bilevel Positive Airway Pressure (BiPAP)) while you sleep? Yes/No
• In the last five years, has your bed partner commented that you snore? Yes/No
• Do any of your blood relatives (NOT those married into the family) have OSA or use a breathing machine while they sleep at night? Yes/No
• Compared to others you know who are drivers, do you notice that you are much sleepier in the daytime than they are? Yes/No

The Epworth Sleepiness Scale

Situation/Chance of Dozing

• Watching television
• Sitting inactive in a public place such as a theatre or a meeting
• As a passenger in a car for an hour without a break
• Lying down to rest in the afternoon when circumstance permits
  
• Sitting quietly after a lunch without alcohol
• In a car, while stopped for a few minutes in traffic    
  

Chance of Dozing - 0 = no chance, 1 = slight, 2 = moderate, 3 = high
Score - 0-9 = normal,10-12 = borderline,13-24 = abnormal

Numerous studies using the Epworth Sleepiness Scale (ESS) have supported high validity and reliability.¹¹ The ESS is a subjective measure of sleepiness with a score of 10 or more being considered sleepy. A high score on the ESS is also a strong indicator of possible OSA.

It is important to note that although the ESS has advantages of being brief and simple to carry out, its limitation is its subjectivity and an individual can over or underscore.

¹ “Obesity Linked To Dangerous Sleep Apnea in Truck Drivers,” Science Daily, www.sciencedaily.com (Mar. 12, 2009).
² Ellen, R. et al, “Systematic Review of Motor Vehicle Crash Risk in Persons with Sleep Apnea,” Journal of Clinical Sleep Medicine (Vol. 2, No. 2, 2006).
³ Hartenbaum, Natalie et al, “Sleep Apnea and Commercial Vehicle Operators,” Statement from the Joint Task Force of the American College of Chest Physicians, the American College of Occupational and Environmental Medicine, and the National Sleep Foundation (Chest 2006; 130:902-905).
⁴ Levy, S., “Obstructive Sleep Apnea and the Commercial Driver: Understanding the Controversy and Applying Screening Criteria,” Western Occupational and Environmental Medical Association, CME Webinar Series (June 16, 2011).
⁵ Ibid., Levy (2011).
⁶ Alvarez, Albert, “Tech Brief: Sleep Apnea Crash Risk Study,” FMCSA, Department of Transportation (September 2004).
⁷ “Sleep Apnea, Risk Factors,” Mayo Clinic, www.mayoclinic.com (accessed August 9, 2011).
⁸ Op. cit., Ellen.
⁹ Op. cit., Levy.
¹⁰ Op. cit., Talmage.
¹¹ Smythe, Carole, “The Epworth Sleepiness Scale (ESS),” The Hartford Institute for Geriatric Nursing (New York University, College of Nursing, Issue Number 6.2, 2007).