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In an interview, Dr. Daniel Perez Chada tells us about his research on fatigue and somnolence in professional drivers in Argentina

October 28, 2016


Neurovirtual News: Doctor, could you tell us a little bit about your background?

Daniel Perez Chada: I am a pulmonologist, and I work at the Hospital Universitario Austral, where I am the head of the pulmonology and Sleep Clinic service; also, since October 2016, I am the chairman of the Argentinean Sleep Foundation.

For many years, I worked in intensive treatment, with a special focus in respiratory failure and mechanical ventilation; I completed my training in Great Bretain, where I worked on basic investigation on mechanical ventilation and pulmonar injury. Throughtout the years, I started focusing on non-invasive ventilation, and, during the last 15 years, I have devoted 80% of my time to the study of respiratory disorders during sleep.

NN: Doctor,  could you tell us about the studies and services offered by the Sleep Clinic at Hospital Universitario Austral?

DC: In the Hospital Universitario Austral our staff studies patients with sleep disorders; we are specially focused on respiratory disorders during sleep. We have a Sleep Clinic with five beds to study patients through nocturnal polysomnography, and eight equipments for ambulatory poligraphy studies.

This is a very committed team, whose members interact with each other actively, besides constituting a strong exchange source with other hospital services, and we have managed to solve most of the sleep apnea problems of our patients.

NN: Doctor, could you tell us something about the investigation you conducted on fatigue and somnolence in professional drivers?

DC: This has been an investigation topic we have been interested in for years given its huge impact on society.

We have done a lot of crossdisciplinary work with basic researchers, mostly with investigators from CONICET, the main organization of  investigation in Argentina.

We trained a team, led by Dr. Daniel Cardinali, a renowned physiologist, with whom we studied the relationship between sleep deficit in professional drivers and the decline in their level of alertness.
We started by studying load transport truck drivers in Mercado Central in Buenos Aires. These drivers are freelancers who transport goods from and to Buenos Aires City, from different locations in the country. We discovered there is a high prevalence of snoring, and, as expected, a connection of this symptom to obesity.

These drivers suffered from high blood pressure and a severe restriction in the amount of hours they slept since they could not sleep for more than four hours per night on weekdays, and tried to make up for this sleep debt on weekends.
This was a group of young men, who chronically slept one hour less than their colleagues, with high prevalence of cardiovascular risk indicators like smoking and obesity.

These are people who, due the characteristics of their job, are not likely to have healthy diet habits, and who are also sedentary. We also found out that those drivers who were regular snorers had more chances of having an accident or were as likely to have an accident during their workday than those who did not snore.

On the other hand, daytime sleepiness was frequent; more than 40% of the drivers felt sleepy while driving. When these people felt sleepy in route, most tried to stop to take a rest; however, there were around 30% of them who adopted absolutely ineffecttive behaviors to fight sleepiness, like smoking, listening to loud music in the truck cab, cooling the cab, drinking carbonated beverages, etc.

Regrettably, the sleep debt is only paid through sleep so these measures are not quite efficient against sleepiness at the wheel.
This was a very interesting investigation that involved more than eight hundred drivers, in their work place, with a structured questionnaire. This has been the first large-scale work on the topic in Argentina; the results were published by SLEEP magazine.

Some years later, we worked with Unión de Tranviarios Automotor, which is the labor union gathering all public passenger transport drivers; we surveyed around two thousand public passenger transport drivers in this group working in Buenos Aires and in the city´s metro area; our finding, once again, was that the amount of hours these drivers slept was reduced, they were obese and experienced cardiovascular comorbidities.

Sleep apnea risk prevalence was present in the sample´s 55%.

Drivers working in the morning shift slept one hour less that those working in the afternoon shift, and it was precisely those drivers working in the morning shift, and chronically sleeping one hour less than their colleagues, the ones whose level of alertness declined, as measured by a very simple and reliable alertness test; these drivers had an earlier decline of alertness than the drivers working in the afternoon shift.

These objective measurements we performed in a small group of drivers included actigraphy for 5 nights, cortisol levels at the beginning and at the end of the workday, and a heart rate variability study.

Finally, we conducted a third study; this time, we studied a request from the Work Risks Superintendence Office, a sample of long distance professional drivers, that is, those drivers transporting passengers to the different regions of the Argentine Republic.

Once again, we performed objective measurements and we confirmed exactly what we had confirmed with the short-distance drivers: sleep hours were scarce, long workdays, and an early decline in alertness in the drivers, particularly on the way back.

Just one question: how did you measure the level of alertness?

DC: Yes, the level of alertness is assessed through a test similar to the psychomotor surveillance test.
When drivers are not at the wheel, but as co-drivers, they are placed in front of a laptop, at various stages during the workday; the screen shows a sequence of numbers and, whenever a number stops on the screen, the subject has to strike any key on the keyboard; the time between the sequence of numbers stopping and the subject striking the key is the reaction time.
What we saw is that the longer the workday the longer the reaction time, which means that the ability to respond to unexpected stimuli, like an animal crossing the road or an unexpected reaction from another driver, or a pedestrian crossing the road unexpectedly, the reaction time to avoid an accident in these situations is also deteriorated.

Doctor, do you think this type of professionals should have a closer follow-up in terms of their sleep disorders?

DC: In fact, the whole of society should know that the number of hours we sleep is below the number of hours we should sleep; during the last fifty years, we have lost 25% of our sleep hours and that is worldwide data, both in the North hemisphere and in the South hemisphere, according to surveys conducted by several organizations, it has been demonstrated that there is a two-hour sleep debt approximately.

Workdays are even longer and there is irrefutable evidence to confirm the fact that if a person is awake for more than fifteen hours, that person has the same chances of making a mistake in a driving simulator than a person who has had the maximum amount of alcohol permitted by law, which means, that being awake for sixteen hours is equal to having, for example, a 0.05 grams/liter Blood Alcohol Content; this BAC, obviously, for a professional driver should be equal to 0, but what I mean is that the restriction in sleep hours produces the same cognitive deterioration as having a blood alcohol content above what is permitted by law.

Obviously, sleep must be ranked in society, particularly for those at a higher risk of exposure such as the professional drivers, both, goods drivers, and passenger drivers, and obviously, campaigns have to be launched so that sleep hours start to be respected, both by workers, and by the companies hiring these workers, as well as by the regulatory entities controlling working shifts.

We also need to bear in mind that there are very prevalent diseases, particularly in males, and particularly in those leading a sedentary lifestyle, such as those who are drivers, which is the sleep apnea syndrome which deteriorates the quality of sleep. Sleep apnea syndrome is a pathology well known for increasing traffic acidents and which, when duly diagnosed and treated, allows people to lead an active and professional lifestyle without this representing a risk to them or to the people sharing the road with them.

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