Coffee is one of the most prevalent beverages consumed worldwide – estimated in 2020/2021 to be around 166.63 million kilograms, a slight increase over 164 million bags in the previous year.
According to “Coffee Consumption and Incident Tachyarrhythmias Reported Behavior, Mendelian Randomization, and their Interactions,” which appeared in July 2021 online in JAMA Internal Medicine, “coffee consumption may have multiple beneficial properties, often attributed to antioxidant and anti-inflammatory effects, and is associated with reduced risks of cancer, diabetes, Parkinson disease, and overall mortality. Indeed, the benefits appear to be most pronounced when caffeinated coffee is consumed.”
Mendelian randomization is a method of using measured variation in genes of known function to examine the causal effect of a modifiable exposure on disease in observational studies.
Tachyarrhythmias are defined as arrhythmia characterized by a rapid irregular heartbeat – “with cardiac arrhythmia at a rate greater than 100 beats per minute,” notes oxfordmedicaleducation.com.
Arrhythmias can occur “when the electrical impulses that coordinate your heartbeats don’t work properly.” comments the Mayo Clinic.
The JAMA investigators, from the Division of Cardiology, Institute for Human Genetics, Department of Epidemiology and Biostatistics, University of California, San Francisco, state that, “although professional society guidelines that suggest avoiding caffeinated products to diminish the risk for arrhythmia have relied on assumed mechanisms and a small observational study from 1980, more recent investigations have consistently not demonstrated an increased risk of tachyarrhythmia among coffee consumers.
The California researchers investigated the association of coffee intake with the risk of tachyarrhythmias in a large, population-based cohort, using participant self-reporting, mendelian randomization, and an analysis of related interactions to elucidate these associations.
The cohort population came from the UK Biobank, a prospective study of 502,543 participants in the UK National Health Services, who were 40 to 69 years of age, and resided within 40 kilometers of 22 assessment centers.
The participants were recruited between January 1, 2006, and December 31, 2010. They completed questionnaires, underwent physical examinations, and provided biological samples.
Coffee consumption, assessed from the participant questionnaires, segmented into 8 categories, which corresponded into the following daily coffee intake: 0, less than 1,1,2,3,4,5, and 6 or more cups daily. Excluded were those people, who answered “do not know” or “prefer not to answer.”
The primary outcome of interest, note the investigators, “was incident tachyarrhythmia, ascertained between January 1, 2006, and December 31, 2018, using International Classification of Diseases, Ninth Revision (ICD-9) and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes available from inpatient and outpatient records.”
Race and ethnicity were ascertained from the baseline survey, while educational level was categorized as middle school graduate, high school graduate, college degree, other professional degrees, and none of the above. Body mass index was based on height and weight.
Physical activity was categorized by the number of days per week of moderate physical activity greater than10 minutes. Hypertension, diabetes, hyperlipidemia, coronary heart disease, congestive heart failure, valvular heart disease, cerebrovascular disease, peripheral artery disease, chronic kidney disease, and cancer were determined by ICD-9 and ICD-10 codes from inpatient and/or outpatient visits between January 1, 2000, and December 31, 2005, commented the California researchers.
The data analysis determined that, “there was no evidence that the association between coffee intake and arrhythmia risk was affected by genetic variants associated with caffeine metabolism. The mendelian randomization analyses failed to provide evidence that caffeine consumption leads to a greater risk of arrhythmias.”