The Migraine Threshold

Have you ever wondered how so many different migraine triggers can produce such similar disabling headaches? How can red wine, flickering lights in an adventure movie, the food additive MSG, and weather changes all act to bring on the same thing, a severe migraine? Why does something like red wine trigger headache in some individuals and not in others? Why does it trigger headache some times and not others in the same individual? Questions like these have long vexed migraine sufferers and headache specialists alike. Over the past few years, researchers have made considerable progress in finding the answers. The topic was recently reviewed by Drs. Vince Martin and Michael M. Behbehani in the journal Medical Clinics of North America.

A migraine trigger is any factor that can lead to the development of a migraine headache. How a specific trigger brings on a headache is becoming more clear, thanks to recent scientific studies on the subject. One leading theory suggests that migraine occurs because of an inherited hyperactivity of the nervous system. Individuals with migraine are genetically programmed to be more vulnerable to irritating stimuli such as flickering lights or sudden changes in weather. When one, two, or several of these irritating stimuli occur, their hyperactive nervous systems respond with a full-blown migraine attack.

According to this theory, migraine-prone individuals simply have a lower threshold for developing migraine. It takes less stimulation of their overactive nerve cells to trigger a headache than is the case for other people. A single glass of red wine may trigger an attack for migraine-prone person, while someone else may be able to drink 4 or 5 glasses before experiencing the throbbing head pain, nausea, and light and noise sensitivity of a migraine.

All triggers are not created equal. The wide variety of triggers has often made tracking and predicting their effects a daunting task. Some bother one migraine sufferer and not another. Some people will have no clearly defined triggers, while others will report many. A specific trigger might bring on a headache 1 time out of 10 or 9 times out of 10.

The concept of the migraine threshold helps to make sense of the seemingly unpredictable nature of triggers. Some people may be strongly sensitive to specific triggers. Others may be vulnerable only when several triggers combine. For example, a tough deadline at work, together with long hours and a missed meal, may bring on a severe migraine in someone who can usually tolerate any one of those triggers (stress, fatigue, fasting) alone.

As summarized by Drs. Martin and Behbehani, population studies have identified many different triggers (see table). This is an inexact science because many triggers may go unnoticed by the migraine sufferer. Headaches can be so disabling that the sufferer may be unable to remember details leading up to the attack. Another variable is the length of time after the exposure before a headache starts. Certain triggers can quickly bring on a headache, whereas other headaches can be delayed for 48 hours or more after exposure to the trigger.

Based on the available scientific evidence, stress, menstruation, caffeine withdrawal, visual stimuli, and weather changes are strongly associated with triggering migraine. Nitrates (in cured meats), fasting, sleep disturbances, wine, MSG, and aspartame are somewhat less strongly associated with consistently bringing on a headache.

Trying to make sense of triggers is a worthy goal for migraine sufferers, as they may be able to prevent attacks by merely avoiding certain dietary, environmental or behavioral triggers. But how? Do they have to forego red wine, action-packed movies in a theater, and late nights out? The answer is--not necessarily. The best advice is to pay attention and to develop a sense of your own migraine threshold--how much you can or cannot do before risking an attack.

First, decide if a rigorous hunt for triggers is even necessary. Someone with occasional, mild, non-disabling headaches does not necessarily have to look for trouble. These fortunate people aren't likely to be significantly affected by triggers.

Second, try to prioritize the triggers. Obviously, you can't avoid everything on the usual lists of potential triggers. Some you can't realistically avoid at all--such as weather changes or, for women, menstruation. Others can be managed with a common sense approach. Limit caffeine consumption to 2 beverages daily. Try to sleep and wake at about the same time every day (including weekends if you have weekend attacks). Eat regularly and avoid skipping meals (very important). Minimize stress by practicing relaxation skills, exercising, or using other anti-stress techniques. Avoid fast moving, flickering lights if possible.

Third, pay attention to possible triggers. Use a headache calendar or diary to keep careful records. Mark when you get a headache, how bad it was on a 1-10 scale, any suspected triggers, and what you did to relieve the pain. Women should also track their menstrual cycles on the calendar.

Fourth, analyze your headache diary for patterns. Try to sort out how consistently a specific trigger seems to lead to a headache--for example, 10%, 50%, or 100% of the time.

Fifth, if your headache pattern is out of control, start with a reasonable trial period of withdrawal of your suspected triggers. For example, set up a 3-month trial of avoiding the more common triggers. If no change is seen, resume the avoided triggers if desired.

Sixth, be aware of the cumulative effects of triggers. Around the time of a woman's period, it may be more important to avoid other triggers such as red wine, sleep deprivation, or skipping meals. If you have a seasonal pattern to your headaches, for example, more attacks in the winter, it is during this time that you should be extra careful about other triggers.

In summary, the typical migraine sufferer is exposed to many potential triggers on a daily basis. These triggers vary from individual to individual. Trying to identify and avoid specific triggers can pay huge dividends. Even if only one or two headaches per month can be avoided by paying more attention to triggers, it is well worth the effort.

Studies of Migraine Trigger Factors

Reported trigger

Scientific evidence supporting the link

% of people with migraine reporting the trigger

Stress/post-stress Strong 36%-51%
Menstruation Strong 8%-54%
Weather changes Strong 7%-52%
Visual stimuli (glare or flickering lights, etc) Strong  
Caffeine withdrawal Strong  
Changes in sleep Moderate 38%
Fasting Moderate 56%
Nitrates (in cured meats) Moderate  
MSG Moderate  
Food Weak to moderate 22%-44%
Chocolate Weak 2%-23%
Smoking Weak 2%-9%

Table and article are derived with permission from Vince Martin, MD, and Michael M. Behbehani, PhD. Toward a Rational Understanding of Migraine Trigger Factors. Medical Clinics of North America 85(4): 911-939, 2001.

Article by Philip Bain, MD, From Headache, The Newsletter of ACHE. Spring 2002, vol. 13, no. 1.