Hospitalizations for Alcohol Linked to Increased Stroke in Low-Risk Atrial Fibrillation

Susan Jeffrey

August 30, 2016

ROME, ITALY — Hospitalization for alcohol-related conditions is associated with a significant increase in the risk for stroke among patients with nonvalvular atrial fibrillation (AF), even those deemed low risk for stroke, a new study suggests[1].

"We need more research to look at this relationship," said Dr Faris Al-Khalili (Karolinska Institutet, Danderyd Hospital, Stockholm, Sweden). In the meantime, clinicians should ask about alcohol use in their patients, he said, even low-risk AF patients, since those with alcohol problems sufficiently severe to be hospitalized may only be the tip of the iceberg in terms of the population at risk for ischemic stroke.

Dr Khalili presented the results here at the European Society of Cardiology (ESC) 2016 Congress.

Therapy Not Indicated

Treatment with oral anticoagulants reduces the risk of stroke and is recommended depending on the number of stroke risk factors, the authors note. Risk is estimated using the CHA2DS2-VASc score that assigns points for clinical risk factors. Patients with nonvalvular AF under the age of 65 and a score of 0 in men or 1 in women are considered to be at low risk for ischemic stroke, and oral anticoagulation therapy is not indicated according to current guidelines.

Dr Faris_Al-Khalili

Despite this low-risk classification, there are nevertheless ischemic strokes that occur among these patients, Al-Khalili said. They suspected that alcohol consumption had a role to play, he said.

"I came on this idea because I'm a clinician, I work with atrial fibrillation, and I meet patients who are in their 40s and early 50s who have no risk at all, but they have atrial fibrillation and they get a stroke, and I just wondered why," he told heartwire from Medscape. "I felt there was something with alcohol—most of these patients, they were excessive drinkers, even if they didn't tell you that straightaway."

The aim of this study, then, was to assess the incidence and predictors of ischemic stroke in this low-risk group with nonvalvular AF, he said. The study was retrospective and included 25,252 low-risk nonvalvular AF patients, aged 18 to 64, out of a total of 345,123 AF patients identified from the Swedish nationwide patient register for the period from January 1, 2006 to December 31, 2012.

The median age of these low-risk patients was 55 years, and 72% were men, he said.

The patient register contains data on all hospitalizations and visits to hospital-affiliated open clinics in Sweden. The 16 alcohol-related diagnoses they used to look at this issue are the same ones used by the Swedish authorities to investigate national issues of alcohol-related mortality, he noted. Some of the diagnoses relate to binge-style drinking, so some of the patients would not fall necessarily into the category of chronic alcohol abusers.

Socioeconomic variables were obtained from a database for health insurance and labor market studies, and data on current medication was obtained from the Swedish National Drug Register.

During a median follow-up of 5 years, ischemic stroke occurred at an annual rate of 3.4 per 1000 patient-years. The overall mortality was 7.5 per 1000 patient-years in patients without ischemic stroke and 29.6 per 1000 patient-years in patients who did suffer an ischemic stroke during follow-up.

In the multivariable analysis, Al-Khalili said, "we saw there were two main predictors [of stroke]: increasing age and alcohol-related hospitalization."

Risk for Stroke in AF (Multivariable Analysis)

Factor Hazard ratio 95% CI P
Increasing age (per incremental year) 1.06 1.05–1.08 <0.001
Alcohol-related hospitalization 2.01 1.45–2.79 <0.001

Use of oral anticoagulants was associated with a lower risk of ischemic stroke (HR 0.78, 95% CI 0.63–0.97; P=0.027).

There is a lot of published work that shows a significant relationship between alcohol and mortality and increased risk for thromboembolism, as well as a link between alcohol use and the incidence of AF, Al-Khalili told heartwire . "But this is the first time that we know that alcohol is a risk factor of ischemic stroke in patients with atrial fibrillation; this is something new."

Using alcohol-related hospitalization as a proxy for alcohol abuse probably underestimates the extent of the problem, he said. "We don't know how much they drank, but it must have been excessive drinking that led them to come to the hospital."

Further investigation should be undertaken to look at the potential benefit seen with oral anticoagulation in this group where anticoagulation is not indicated in current guidelines, he noted in a statement.

Dr Gerhard Kindricks (Herzzentrum-Leipzig Universitätsklinik, Germany) moderated a press conference here that featured this paper.

"As always in these situations, the key question is 'why?' " Kindricks commented. "It's impressive to look at this large Swedish cohort; I think it's new and very, very interesting to learn that there is an association between alcohol intake obviously and stroke risk in nonanticoagulated patients with a low stroke risk according to CHA2DS2-VASc score."

The "why" could arise from a number of factors, he said. "On the one hand, it could be that actually the patients were undertreated due to the fact that they were not correctly coded and that simply some states of disease were overlooked," Kindricks speculated. "The second would be that alcohol intake, hard-core drinking, relates to transient impairment of left ventricular function and changes stroke risk thereby.

"And the third is that metabolic or structural changes are induced by alcohol intake that can lead to an increase in stroke risk that is not detected by the CHA2DS2-VASc," he said.

The study received no outside funding. Al-Khalili reported no relevant financial relationships.

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