Flying and Health — Page 112, Lesson 171

I want to walk you through a topic that directly affects your performance in the cockpit: caffeine and its effects on the body, followed by a brief but critical note on psychiatric illnesses. Let’s start with caffeine. Caffeine is a diuretic — that means it makes your body produce more urine, which can increase the risk of dehydration. This is especially important for us as aircrew because the relative humidity in an aircraft cabin is already very low, so we are already losing moisture through breathing and skin. Adding caffeine on top of that accelerates fluid loss. Caffeine enters your bloodstream very quickly — it is found in the blood only 10 minutes after you ingest it. It also has a half-life of approximately 4 hours. A half-life means that after 4 hours, half of the caffeine you consumed is still active in your system. After another 4 hours, half of that remaining amount is still there, and so on. So if you have a coffee at 8 AM, by noon you still have about half the caffeine working in your body. Now, regular intake of caffeine over a long period can lead to several serious health problems. The book lists: ulcers and other digestive disorders, increased risk of cardiac arrest, hypertension (which is high blood pressure), personality disorders, chronic muscle tension, insomnia (difficulty sleeping), disorientation, and hyperactiveness — especially in children. There is also a withdrawal syndrome. If you are a regular caffeine user and you stop, withdrawal symptoms typically appear 12 to 16 hours after your last dose. These include: irritability, sluggishness, headaches, depression, drowsiness, lethargy, and in more serious cases, occasional nausea and vomiting. Let’s look at the approximate caffeine content of common sources, because you need to know what you are actually consuming. A cup of brewed coffee contains 80 to 135 milligrams of caffeine. A cup of instant coffee has 65 to 100 milligrams. Decaffeinated coffee still has a small amount — 3 to 4 milligrams. A cup of espresso coffee contains about 100 milligrams. A cup of black tea has 30 to 70 milligrams. An average 12-ounce can of cola contains 30 to 60 milligrams. A bar of dark chocolate has about 30 milligrams. Even an average cold relief tablet contains 30 milligrams of caffeine — so you need to account for that if you take medication. A can of 7Up contains zero caffeine. The book gives a clear recommendation for aircrew: the absolute maximum caffeine limit of approximately 250 to 300 milligrams per day should be rigorously respected. That translates to about 2 to 3 cups of coffee. This is not a suggestion — it is a limit you should treat as a professional standard. Now, moving to a completely different topic: psychiatric illnesses. The book states that serious forms of psychiatric illness associated with loss of insight or contact with reality — specifically a psychosis such as bipolar disorder (also called manic depression) or schizophrenia — will always result in the permanent loss of a flying licence. This is a hard rule. If a pilot develops one of these conditions, they are permanently medically disqualified from flying.