Re: Alcohol consumption and risk of dementia: 23 year follow-up of Whitehall II cohort study
Examining the association between alcohol consumption and cognitive impairment is fraught with methodological difficulties and the results from this study should be interpreted with a high degree of caution. The study tells us little about how drinking above low risk guidance beyond the of age of 55 affects the development of dementia. We know that a third of older people with alcohol misuse develop this for the first time in later life. This group would not have been included in the study.
Although the finding regarding an association between dementia risk and progressively higher alcohol consumption above current UK government guidance replicates similar research, it is known that people with a history of heavy drinking may abstain for health reasons or people with health problems may choose not to drink. Both these possibilities can easily influence any meaningful interpretation of these results.
However, the elephant in the room here is the definition of alcohol related dementia. The inclusion criteria for this study was based largely on ICD diagnostic categories for Alzheimer's Disease using both "F" and "G" codes. It did not include the one diagnostic category that actually describes alcohol related dementia (F10.73). This is hidden away in the descriptor "Residual and Late Onset Psychotic Disorders".
Alcohol related dementia differs from other dementias in its clinical characteristics, including areas of cognitive impairment[1, 2} . Until we start using a more valid definition of alcohol related dementia, we are going to continue to be misled by research that uses degenerative and vascular dementia (which presents with a similar predilection for frontal lobe impairment)  as the basis for examining attribution and association.
1) Rao RT, Draper B. Addressing alcohol-related dementia should involve better detection, not watchful waiting. The British Journal of Psychiatry. 2018 Feb;212(2):67-8.
3) Rao R. Cognitive impairment in older people with alcohol use disorders in a UK community mental health service. Advances in Dual Diagnosis. 2016 Nov 21;9(4):154-8.
3) Bonnici-Mallia AM, Barbara C, Rao R. Vascular cognitive impairment and vascular dementia. InnovAiT. 2018 May;11(5):249-55.
Competing interests: No competing interests