Studies of the health effects of alcohol consumption may underestimate the risks of imbibing, particularly for younger people, according to a US study. This is because cohort studies generally do not encompass the full age spectrum of adults or represent all people who drink alcohol.
Although cohort studies – the type of observational investigations typically used to study health benefits and risks – sometimes show benefits from moderate alcohol consumption, they tend to enrol people age 50 and older. Studying people at this age range eliminates all those who have died before age 50 because of alcohol consumption.
Simply put, “deceased persons cannot be enrolled in cohort studies”, write the authors led by Dr Timothy Naimi of the Boston Medical Centre. “Those who are established drinkers at age 50 are ‘survivors’ of their alcohol consumption who (initially) might have been healthier or have had safer drinking patterns” compared with others.
In fact, more than 40% of overall deaths from alcohol occur before age 50, according to the study. This suggests that most current studies underestimate alcohol-related risk compared with what would be observed across the full age spectrum. Further, the study demonstrates that most study participants are not representative of all persons who begin to drink alcohol.
To obtain data for the current research, Naimi and his colleagues used the Alcohol-Related Disease Impact software application from the US Centres for Disease Control and Prevention. The data used were derived from government statistics on cause of death and health benefits from 2006 to 2010 in the US.
Naimi and colleagues found age was a large factor in deaths prevented by alcohol consumption. Some 35.8% of the total deaths caused by alcohol occurred in people ages 20 to 49. However, of the deaths determined to have been prevented by alcohol consumption, only 4.5% occurred in this younger age group.
Although those ages 65 and older saw a similar 35.0% of the mortality caused by drinking, 80% of the deaths that were prevented by alcohol consumption occurred in this group.
A somewhat similar pattern emerged when the researchers looked at years of potential life lost as a result of drinking. Of the overall years of life lost, 58.4% occurred in those ages 20 to 49. But this younger group saw only 14.5% of the years of life saved from drinking.
People 65 and older accounted for 15% of the overall years of life lost from alcohol consumption. However, more than 50% of the years of life saved occurred within this older group.
In general, their results show that younger people “are more likely to die from alcohol consumption than they are to die from a lack of drinking,” according to the authors, whereas older people are the ones most likely to see the health benefits of moderate drinking often mentioned in the news.
“This study adds to the literature questioning protective effects for alcohol on all-cause mortality,” the authors conclude. Nonetheless, they write that “most who choose to drink can do so with relatively low risk.”
Alcohol, Age and Mortality: Estimating selection bias due to premature death
Journal of Studies on Alcohol and Drugs
Timothy S Naimi, Lyndsey A Stadtmueller, Tanya Chikritzhs, Tim Stockwell, Jinui Zhao, Annie Britton, Richard Saitz and Adam Sherk, Adam
Alcohol use causes approximately 10% of deaths among adults ages 20–65 in the United States. Although previous research has demonstrated differential age-related risk relationships, it is difficult to estimate the magnitude of selection bias attributable to premature mortality based on existing cohort studies, the average age of which is greater than 50 years. The objective of our study was to assess the distribution of mortality-related harms and benefits from alcohol among adults ages 20 and older in comparison with the distribution among those older than age 50.
Data from the Centers for Disease Control and Prevention’s Alcohol-Related Disease Impact software application from 2006–10 were used to determine the distribution of alcohol-attributable deaths (AADs) and the years of potential life lost (YPLLs) that was caused or prevented by alcohol for 54 conditions by 15-year age groupings (20–34, 35–49, 50–64, 65+) in the United States. We also determined the proportion of net deaths and YPLLs occurring in each age group, overall and by cause of death.
Adults ages 20–49 years experienced 35.8% of the deaths and 58.4% of the YPLLs caused by alcohol, whereas the same group accrued only 4.5% of AADs and 14.2% of YPLLs gained. Overall, 46.3% of the total net deaths and 64.7% of the net YPLLs occurred among those ages 20–49; adding net deaths occurring among those ages 20–49 to those occurring after age 50 would result in an 86.3% relative increase in net deaths.
Because of premature mortality, alcohol-mortality associations based on cohort studies may underestimate negative health consequences compared with those observed among the general population.