"This may be due to the fact that adults who are able to continue consuming alcohol into old age are healthier, and therefore have higher cognition and larger regional brain volumes, than people who had to decrease their alcohol consumption due to unfavourable health outcomes," he added.
Findings from animal studies suggest that moderate alcohol consumption may help to preserve hippocampal volume - the area of the brain critical for memory - by promoting generation of new nerve cells.
Exposing the brain to moderate amounts of alcohol may also increase the release of brain chemicals involved with cognitive functions, scientists said.
The study also found that most people drank less in old age than in middle age and that middle-aged men were more likely than middle-aged women to drink heavily.
Those aged over 60 who did not drink at all were less likely to have gone through higher education and were also less likely to have smoked when they were younger.
The amount of alcohol consumption had no impact on overall mental ability.
The report stated: "There were significant differences in cognitive functioning according to late life, but not midlife, alcohol consumption status.
"Patients who were light alcohol consumers during late life had significantly higher episodic memory compared with late life abstainers, whereas no significant differences between moderate and heavy alcohol consumers were detected compared with abstainers."
The findings were published in the American Journal of Alzheimer's Disease and Other Dementias.