It is well established that people with alcohol use disorder (AUD) have a higher risk of dying early than those without this disorder. In a study published in 2016 in JAMA Psychiatry, Ken Kendler and colleagues reported a 5.8-fold increase in mortality rates for those with AUD (Mortality rate can be defined as the number of deaths in a certain population per unit time). These researchers examined whether the reasons for the increased death rate in individuals with AUD were similar in younger and older individuals. Specifically, they wanted to know if alcohol consumption directly led to the increased death rate or whether personality traits and environmental conditions associated with AUD led to the markedly increased death rate. For example, people who are prone to develop AUD may have personality traits such as impulsivity that lead to increased deaths independent of the drug itself.
How can one study this question? Kendler’s group took advantage of the national health registers in Sweden to study a sample of almost three million individuals. This population included a significant number of identical twins, so the research team was able to examine death rates in twins who were discordant for AUD, i.e., one of the twins had AUD and the other twin did not. Identical twins share all of their genes, and those growing up together usually live in a similar environment. Many behaviors are highly inherited, and twin studies are a way to assess heritability. If alcohol consumption causes a direct effect on the increase in death rates, then the twin with AUD should have a markedly increased rate of death compared to the twin without AUD. If the increase in death rate is a result of shared behaviors and/or shared environment, then the twin with AUD and the one without AUD should have rates of death that are similar to each other and comparable to the entire sample of people with AUD. The investigators were also interested in comparing mortality rates in discordant twin pairs at different ages.
The results of this study indicated that the increased death rate associated with AUD resulted from inherited behavioral traits and environmental conditions in individuals less than 30 years old. In this age group, the rates of death were elevated to the same degree in both the twins without AUD and the twins with AUD. However, in those 60 and above, the death rate in the twins with AUD was much higher than the twins without AUD. In other words, increased alcohol consumption was directly responsible for the increase in death rates rather than the shared genes, behaviors, and environment.
The highest increase in mortality rate—over an 8-fold increase in death rate—occurred in individuals 30 to 39 years old. In this age group, both the direct effects of alcohol and the behavioral or environmental influences contributed to the increase.
Based on these results, it would be reasonable to focus therapeutic efforts in older individuals on achieving abstinence and on maintaining a healthy life style, including treating any chronic medical conditions and nutritional deficits. In younger individuals, encouraging abstinence is essential to decrease the risks of long-term use, but treatment should also heavily concentrate on diminishing risky behaviors.
This research is an excellent example of utilizing data from national registries and twin-based research approaches to better categorize different reasons for higher death rates in younger and older individuals. Such information has direct implications in choosing the most appropriate treatments and interventions.
This article was written by Eugene Rubin MD, PhD and Charles Zorumski MD.
Kendler, K.S., Ohlsson, H., Sundquist, J., & Sundquist, K. (2016). JAMA Psychiatry, 73, 575-581.