Why Do Only Some Cohort Studies Find Health Benefits From Low-Volume Alcohol Use? A Systematic Review and Meta-Analysis of Study Characteristics That May Bias Mortality Risk Estimates

This study looks at how certain factors in research can skew the results when estimating the health effects of drinking small amounts of alcohol. These biases can affect public health advice and shape how people view alcohol’s potential health benefits.

Method:
- Data Collection: The researchers reviewed 107 studies with 4.8 million participants and over 425,000 recorded deaths, analyzing 724 estimates of how drinking affects the overall risk of death.
- Study Criteria: Higher-quality studies included participants aged 55 or younger, followed them past age 55, and excluded former or occasional drinkers from the non-drinker group. Low-volume drinking was defined as one drink per week to two drinks per day.
- Analysis: The researchers used statistical modelling to compare mortality risks in higher-quality studies versus lower-quality ones.

Results:
- Studies with younger groups that excluded former or occasional drinkers found no difference in death risk between low-volume drinkers and non-drinkers (Risk = 0.98).
- Studies that didn’t meet these criteria showed a lower risk of death for low-volume drinkers (Risk = 0.84).
- Studies that controlled for smoking and socioeconomic status also found lower risks for low-volume drinkers. Still, those that specifically looked at non-smokers showed a slight increase in risk (Risk = 1.16).

Conclusions:
Many studies have biases that can make it seem like drinking small amounts of alcohol is good for your health. These biases are common in alcohol research and can mislead people about the real risks of drinking. Future research should look more closely at how smoking might affect the link between alcohol use and health outcomes.