Is Alcohol Abuse a Bigger Dementia Risk Than We Thought?

Scientists have long known that too much alcohol can do a number on cognition, but the evidence was spotty and the magnitude of the problem unclear. Now, a massive study of hospital patients in France finds that heavy drinking triples the risk of dementia and leads to more than half of earlier-onset cases. Reporting in the February 20 Lancet Public Health, scientists led by Michaël Schwarzinger, Translational Health Economics Network (THEN), Paris, and Jürgen Rehm, University of Toronto, suggest alcohol abuse should be added to the list of major risk factors for dementia about which people can do something. They argue for more diligent screening and treatment.

“This study is immensely important and highlights the potential of alcohol use disorders, and possibly alcohol consumption, as modifiable risk factors for dementia prevention,” wrote Clive Ballard and Iain Lang, both at the University of Exeter Medical School, U.K., in a Lancet commentary.

Many studies on alcohol use and dementia have focused on the health benefits of moderate drinking. Few have examined if heavy use hastens disease, and only some have made a connection to dementia (for a review, see Ridley et al., 2013; Topiwala et al., 2017). Alcohol use is not one of the nine modifiable risk factors included in “Dementia Prevention, Intervention, and Care,” a report commissioned by The Lancet, or as one of the modifiable risk factors suggested by the National Academies of Science, Engineering, and Medicine in its report last June (Aug 2017 conference news on Livingston et al., 2017; Jun 2017 news). Gill Livingston, University College London, who led the Lancet commission, told Alzforum they recognized that alcohol consumption could be important but lacked the data to include it in risk calculations. However, more evidence has become available recently and will appear in the commission’s newest assessment, which is in preparation, she added.

To get a handle on the population-wide link between alcohol abuse and dementia, Schwarzinger and colleagues turned to a database of medical records for 31.6 million people older than 20 who were discharged from French hospitals between 2008 and 2013. The database included patient demographics such as age and sex, plus discharge diagnosis codes, which cover various forms of dementia and alcohol use disorders. Since France provides universal health care, this study captured half of all French adults younger than 65 and 80 percent of people over 65 who were hospitalized in this period for any reason. The researchers excluded anyone who might have had a known type of cognitive decline, for example from HIV/AIDS or Huntington’s disease. They also controlled for vascular risk factors, cerebrovascular disease, educational level, depression, and hearing or visual impairment.

Of the 30.5 million people who were included in the final analysis, 1,109,343 had dementia—57,353 of them before age 65. Of the same 30.5 million, 945,512 people had an alcohol use disorder, and in 87,659 cases, the two diagnoses overlapped. For both women and men, alcohol abuse more than tripled the risk for dementia, and emerged as the strongest modifiable risk factor for the disease, beating out smoking, obesity, high blood pressure, and diabetes. In addition, the authors estimated that 56 percent of early onset sporadic dementia cases were a direct result of, or co-diagnosed with, alcohol use disorders (see image above).

The results suggest heavy drinking has strong links to dementia, especially cases that occur before age 65, wrote the authors. Interestingly, while abstaining from alcohol after a period of abuse reduced a patient’s odds of dying in the hospital, it had no impact on risk for dementia onset. “This study supports that heavy drinking incurs lifelong brain damage,” Schwarzinger wrote to Alzforum.

“This is a very large nationwide sample over a five-year period, and adds to the evidence that alcohol use disorders can increase risks of dementia,” wrote Brian Draper, University of New South Wales, Sydney, to Alzforum. A general decline in drinking has been seen since 1960, and further modeling will be required to determine if that explains falling dementia trends in developed countries, Schwarzinger added (Sep 2017 news; Nov 2016 news). Meanwhile, health care providers should be alert to the association between excessive alcohol consumption and cognitive decline. They could employ earlier and more aggressive screening and interventions to reduce its burden in the population, he said.

Ballard noted that alcohol consumption is often accompanied by poor diet and lifestyle, smoking, cardiovascular disease, depression, failure to comply with medical treatments, and social isolation. “Understanding the pathways of risk in people with alcohol use disorders will help us to model the attributable risk more accurately and to develop better prevention strategies,” he wrote.—Gwyneth Dickey Zakaib