As a class, people who don't drink at all have a higher mortality risk than light drinkers. But nondrinkers are a diverse bunch, and the reasons people have for abstaining affects their individual mortality risk, in some cases lowering it on par with the risk for light drinkers, according to a University of Colorado study.
Multiple studies have shown that the likelihood of dying for people who drink increases as they consume more alcohol. Those same studies have shown that a person's mortality risk also increases at the other end of the spectrum - among people who choose not to drink at all - though the risk is still much less than for heavy drinkers.
Some researchers have hypothesized that the increased mortality among nondrinkers could be related to the fact that light alcohol consumption - drinking, on average, less than one drink a day - might actually protect people from disease and reduce their stress levels.
But researchers at the University of Colorado Boulder, working with colleagues at the University of Colorado Denver, decided to examine whether characteristics of different subgroups of nondrinkers could explain the increased mortality risk.
"Among nondrinkers, people have all sorts of background reasons for why they don't drink," said sociology Professor Richard Rogers, director of CU-Boulder's Population Program in the Institute of Behavioral Science. "We wanted to tease that out because it's not really informative to just assume that nondrinkers are a unified group."
For the new study, published in last month's issue of the journal Population Research and Policy Review, Rogers and his colleagues relied on data collected in 1988 by the National Health Interview Survey about the drinking habits of more than 41,000 people from across the United States. The researchers also had access to information about which respondents died between taking the survey and 2006.
During the survey, nondrinkers were asked to provide their reasons for not drinking. Possible answers ranged from "don't socialize very much" to "am an alcoholic" to "religious or moral reasons."
The research team divided nondrinkers into three general categories: "abstainers," or people who have never had more than 12 drinks in their lives; "infrequent drinkers," or people who have fewer than 12 drinks a year; and "former drinkers." Each category was further divided using a statistical technique that grouped people together who gave similar clusters of reasons for not drinking.
The team then calculated the mortality risk for each subgroup compared with the mortality risk for light drinkers, and they found that the risks varied markedly.
Abstainers who chose not to drink for a cluster of reasons that included religious or moral motivations, being brought up not to drink, responsibilities to their family, as well as not liking the taste, had similar mortality risks over the follow-up period to light drinkers.
"So this idea that nondrinkers always have higher mortality than light drinkers isn't true," Rogers said. "You can find some groups of nondrinkers who have similar mortality risks to light drinkers."
The other subgroup of abstainers - whose largest reason for not drinking appeared to be a dislike of the taste and to a lesser degree family responsibilities, religious or moral motivations or upbringing - had a 17 percent higher mortality risk over the follow-up period compared with light drinkers.
The scientists also found that infrequent drinkers generally had a slightly higher mortality risk than light drinkers. Former drinkers, however, had the highest mortality risk of all nondrinkers. Former drinkers whose cluster of reasons for not drinking now included being an alcoholic and problems with drinking, for example, had a 38 percent higher mortality risk than light drinkers over the follow-up period.
By comparison, people who drink between one and two drinks per day, on average, have a 9 percent higher mortality rate than light drinkers, while people who drink between two and three drinks per day have a 49 percent higher mortality. People who consume more than three drinks per day had a 58 percent higher mortality risk over the follow-up period compared with light drinkers.
Despite confirming that some subgroups of nondrinkers have a higher mortality rate than light drinkers, it doesn't necessarily follow that those people's mortality rates would fall if they began drinking, Rogers said. For example, people who were problem drinkers in the past might increase their mortality risk further by starting to drink again.
Also, people who don't drink at all, as a group, have lower socioeconomic characteristics than light drinkers, which could be one of the underlying causes for the mortality differences, Rogers said. In that case, starting to drink without changing a person's socioeconomic status also would not likely lower mortality rates.
"I think the idea that drinking could be somewhat beneficial seems like it's overstated," Rogers said. "There may be other factors that lower mortality for light drinkers. It's not just the act of drinking."