J-curve – can also be found with moderate consumption of alcoholic beverages and neurological disorders
Alcohol use is associated with a wide spectrum of neurological disorders, including cognitive dysfunction and dementia. A high consumption of alcoholic beverages increases the risk of these and other neurological disorders. In contrast, low to moderate consumption was found to have either no or reduced risks. Because the results about alcoholic beverages and cognitive dysfunction and dementia have been inconsistent, the current systematic review and dose-response meta-analysis of prospective cohort studies intended to update the overall evidence on the intake of alcoholic beverages and cognitive dysfunction and address limitations of the previous meta-analyses.
Cognitive dysfunction is a common condition among older adults and the number of cases is expected to increase greatly by 2050 due to the larger number of individuals surviving to older ages. Since treatments for cognitive dysfunction so far have had limited benefit, identifying modifiable risk factors is important. Several lifestyle factors (poor diet, smoking, consumption of alcoholic beverages and sedentary lifestyle) have been associated with cognitive impairments in older persons. High alcohol consumption increases the risk of several chronic diseases including cognitive impairment and dementia. however, low-to-moderate alcohol intake has been associated with lower risks in some studies.
The current evaluation updated two earlier meta-analyses and paid particular attention to the dose-dependent effects. 17 studies – carried out between 1997 and 2018 lasting an average of twelve and a half years – were included in this meta-analysis.
The results showed no linear relationship between the highest and lowest consumption of alcoholic beverages and the risk of suffering cognitive impairment. However, when the data were analyzed in a dose-dependent manner, a J-shaped relationship – as in many previous studies – was found: up to an amount of 30 g of alcohol per day, the risk of cognitive impairment was slightly (-3%) but statistically significantly reduced compared to abstinence. This amount is equivalent to approximately 300 ml of wine. The findings for dementia were similar: there was no significant association when comparing the highest with the lowest consumption of alcoholic beverages compared to abstinence.
The authors concluded that according to the dose-response meta-analysis, there was a strong evidence of a non-linear (J-shaped) association between the moderate consumption of alcoholic beverages and the risk of cognitive dysfunction and dementia. Their findings suggested that light-to-moderate consumption of alcoholic beverages, an intake of 30 g/day (~ 2-3 glasses of wine), was associated with the greatest reduction in cognitive dysfunction risk, and an intake of 15 g/day was related to the greatest reduction in dementia risk (~ 150 ml of wine).
There was not enough data to distinguish between the type of alcoholic beverage or the drinking patterns. The findings come from observational studies that cannot provide cause-and-effect evidence and should be interpreted with caution. Based on the results presented here, it can be said that light to moderate consumption of alcoholic beverages can be associated with slightly reduced risks for the neurological disorders. Further investigations have to show now, whether this could be due to the type of drink, drinking patterns, lifestyle in general, certain ingredients such as the polyphenols in wine or other factors.
