Doctors often ask their patients to estimate how much alcohol they consume in a week. If the answer is “Ten drinks a week,” it could be five drinks a night twice a week, or two drinks a night five days a week, or something in between.

The pattern of the drinking is what's important and unless told to your doctor can significantly hide alcohol's health impact. Though moderate alcohol consumption is considered beneficial for health and longevity, if it includes a night of binge drinking, the exact opposite may be true.

It’s not just a young person’s problem. Middle-aged and older adults may also have heavy drinking episodes. And it can be even harder on their health.

The National Institute on Alcohol Abuse and Alcoholism defines binge drinking as a pattern of drinking that brings a person’s blood alcohol concentration (BAC) to 0.08 grams percent or above. This typically happens when men consume five or more drinks, and when women consume four or more drinks, in about two hours.

In a new study, researchers followed people over a 20-year period. After giving the participants detailed questionnaires, they found that 372 were moderate drinkers who never binged. Another 74 were moderate drinkers who sometimes engaged in binge drinking, or episodic heavy drinking. The team monitored how many of the participants died over the next two decades.

“We found that among older adults, those who engage in heavy episodic drinking — even when average consumption is moderate — show significantly increased total mortality risk compared to regular moderate drinkers,” study author Charles J. Holahan said in a statement.

Binge drinking is linked to a greater risk of mortality for two reasons. One is that alcohol is much more concentrated during these episodes, so its toxicity, and resulting effects on the organs, is also exaggerated. The other reason is that during a heavy drinking episode, people are more likely to engage in risky and destructive behaviors, such as fights or domestic violence, and to be involved in accidents like car crashes or falls.

Researchers and healthcare professionals are becoming more aware of both the risks of binge drinking and of the surprising regularity with which people seem to engage in it. It’s not just a young person’s problem, the authors point out. Middle-aged and older adults may also have heavy drinking episodes. And it can be even harder on their health, since their physical “reserves” are generally less than those of a younger person.

That's why it’s important for doctors to ask their patients not just how much they drink on average, but how many drinks they may have in one sitting. As Timothy Naimi, a physician and alcohol researcher at Boston Medical Center at Boston University, pointed out in comments on the study, “Approximately a quarter of ‘moderate’ drinkers report binge drinking, and most folks in the US don't typically drink in an 'average' way or on a daily basis.”

Moderate drinking may still be all right in the long-run, provided that it is indeed moderate. But if a person's alcohol consumption includes episodes of binging, the effect on health may be very different. As Naimi says, “It's not just how much you drink but how you drink. ”

The research was carried out by a team at the University of Texas at Austin and the Center for Health Care Evaluation at Stanford University. It is published in Alcoholism: Clinical & Experimental Research .