Alcohol is the number one modifiable risk factor for dementia

There is an ongoing interest in the relationship between alcohol use, cognitive health, and dementia specifically. Previous research has presented inconsistent results with some evidence suggesting that light-to-moderate drinking has a positive effect on cognition, while moderate drinking can cause damage to brain structure (Rehm et al, 2017; Verbaten, 2009). Heavy drinking, on the other hand, has been associated with functional brain damage caused by ethanol, thiamine deficiency and vascular problems (high blood pressure, stroke, heart failure).

Mental Elf blogger, Josephine Neale, blogged about the World Alzheimer’s Report on evidence for protective and risk factors for dementia (Neale, J. 2014). It was suggested that heavy or excessive drinkers had similar risks to non-drinkers and those who only drank wine had similar risks to non-drinkers. So surely, the French have nothing to worry about, right?

This blog summarises the findings of a recent retrospective study examining the association between alcohol use disorders and dementia risk, in a retrospective cohort in France between 2008 and 2013 (Schwarzinger et al, 2018).

Red wine is often portrayed in the media as the ‘healthy’ alcoholic drink, so surely, the French have nothing to worry about, right?

Methods

Data was extracted retrospectively from the French National Hospital Discharge database. This database included standardised discharge summaries of demographics, primary and associated discharge diagnoses using WHO ICD-10, medical procedures, length of stay and discharge modes.

The authors searched discharge summaries for all adults aged 20 or over living in metropolitan France who were discharged between 2008 and 2013. They applied exclusion criteria according to ICD-10 taxonomy.

Exclusions

Individuals with diseases leading to rare types of dementia (F02): infectious diseases, HIV/AIDS, hereditary metabolic disorders, hereditary neurological disorders such as Huntington’s disease, other neurological disorders such as Parkinson’s disease and systemic connective tissue disorders
Individuals with early-life mental disorders, that could increase or confound dementia diagnosis: cerebral palsy, Down’s syndrome, learning disabilities and schizophrenia. (A full coding dictionary was included in the appendices).

Primary exposure

Alcohol use disorders defined, using ICD-10, as the chronic and harmful use of alcohol or alcohol dependence.

Discharge diagnosis

Two categories of discharge diagnosis (applying ICD-10 codes):

Mental and behavioral disorders due to former or current chronic harmful use of alcohol including alcohol abstinence
Chronic disease attributable to alcohol use disorders (Wernicke-Korsakoff syndrome, end stage liver disease and other forms of liver cirrhosis, epilepsy and head injury).

Primary outcome

Dementia, defined by any primary or associated discharge diagnosis (ICD-10) codes labelling dementia or related to dementia.

Dementia onset was reported as the age at first dementia diagnosis between 2008 and 2013. Diagnoses made before age 65 were classified at early-onset diagnosis.

Dementia onset was separated into three categories:

Alcohol-related brain damage
Vascular dementia
Other dementia including Alzheimer Disease.

Other risk factors extracted from the database included vascular risk factors (tobacco, smoking, obesity, high blood pressure, hyperlipidemia and diabetes), cardiovascular risk factors (hemorrhagic stroke, ischaemic stroke, history of stroke, history of IA and CC disease.), depression and hearing loss.

Other diseases (i.e. visual impairment, sleep apnoea) that might lead to rare cases of dementia were also controlled for.

Educational level was estimated using 5645 postal codes of residency as a proxy of educational level for each geographical area.

Results

31.6 million adults were discharged from French hospitals during 2008-2013. Approximately 1 million (3.4%) were excluded based on exclusion criteria noted above
1.1 million adults included in the study had a diagnosis of dementia of which 64.9% were women. This proportion was different for the early onset (aged <65 years) cases; 5.2% of total dementia cases were early-onset and of those, nearly 65% of those were men
3.1% of total adults included in the study were discharged with alcohol use disorders (5.5% of men and 1.3% of women)
For the dementia cases, alcohol-related brain damage was recorded in 35,034 (3.1%) and other alcohol use disorders in 52,625 (4.7%). Both these conditions were more frequent in men (74.5% and 66.5% respectively) and were found in over half early onset dementia cases
The authors also investigated risk factors for adults with dementia discharged between 2011-2013 who had no diagnosis of dementia between 2008 and 2010. They did this because delays in the diagnosis of dementia can lead to reverse causation
- It was found that 2.2% of men and 2.8% of women discharged in this time were newly diagnosed with dementia. There were significantly fewer cases of alcohol-related brain damage and vascular dementia in women than in men (p<0.0001)
Alcohol use disorders were associated with an increased risk for dementia onset which was similar in both men (HR=3.36. 95% CI: 3.31 to 3.41) and women (HR=3.34, 95%, CI 3.28 to 3.41) and were the strongest modifiable risk factor for dementia
Multivariate Cox analyses showed that alcohol use disorders remained associated with increased risk for each dementia type (vascular dementia: HR: 2.30, 95%, CI 2.24 to 2.36 and other dementias: HR: 2.36, 95%, CI: 2.31 to 2.42)
The same independent risk factors (adjusted HRs>1) for dementia onset were identified for both sexes including all alcohol-related conditions, tobacco smoking, high BP and diabetes amongst vascular risk factors hemorrhagic stroke, ischaemic stroke, history of stroke, peripheral arterial disease, atrial fibrillation and heart failure for cardiovascular disease
All independent risk factors apart from depression and hypothyroidism all were more frequently reported in men
Finally, the authors also conducted sensitivity and falsification analyses to support their results. This showed a strong association between alcohol use disorders and dementia onset.

This evidence suggests that drinking alcohol is the number one modifiable risk factor for dementia.

Conclusions

Alcohol use disorders are associated with all types of dementia and especially early onset dementia, even after controlling for confounding risk factors.

Alcohol use disorders are a risk factors for dementia in men and women although they are more frequently reported in men.

There is clear evidence that the impact of alcohol on dementia is much larger than previously thought and ought to be taken into consideration as a risk factor for dementia.

Even after controlling for confounding risk factors, this study found that alcohol use disorders are associated with all types of dementia and especially early onset dementia.

Strengths and limitations

The authors noted that more than 80% of French adults over 65 were admitted to hospital over the study period, which means that the results can be generalised to the French population. The availability of standardised discharge summaries gave a real advantage to carrying out a study like this allowing to consider confounding factors. Also, a systematic approach was used in extracting data using an established classification system for alcohol use disorders and dementia.

The prevalence of alcohol use disorders in France is close to the EU mean (Rehm et al 2015), so the results are of significance for the other European countries including the UK.

A limitation noted by the authors included the fact that dementia diagnosis was not confirmed by brain biopsy as is the case with most epidemiological studies. It is also likely that only very severe cases of alcohol use disorders were recorded in hospitals as there is a taboo around the subject of alcohol related disorders and it may be that alcohol use disorders are underestimated in the study.

Furthermore, although a significant proportion of total dementia cases had alcohol use disorders (4.7%) and alcohol related brain damage (3.1%), the majority did not. Our understanding of milder, non-disordered alcohol use and risk of dementia still needs further exploring.

This evidence doesn’t tell us how much alcohol is too much, in terms of our increased risk of dementia. There remains conflicting evidence on the benefits and harms of light to moderate alcohol use on dementia risk.

Implications for practice

Alcohol use disorders should be recognised as a major risk factor for all types of dementia and clinicians should be aware of the role of alcohol use disorders in dementia onset over the lifetime.

Identifying alcohol use problems early can help to provide intervention and support in managing the risk of future dementia.

Conflicts of interest

None

Links

Primary paper

Schwarzinger M, Pollock BG, Hasan OSM, et al. (2018) Contribution of alcohol use disorders to the burden of dementia in France 2008–13: a nationwide retrospective cohort study. Lancet Public Health 2018; published online Feb 20. http://dx.doi.org/10.1016/S2468-2667(18)30022-7.

Other references

Neale J. (2014) Risk factors for dementia: separating the facts from the myths. The Mental Elf, 12 Nov 2014.

Rehm, J, Gmel, GE Snr., Gmel, GE et al. (2017). The relationship between different dimensions of alcohol use and the burden of disease- an update. Addiction; 112; 986-1001.

Verbaten, M.N. (2009). Chronic effects of low to moderate alcohol consumption on structural and functional properties of the brain: beneficial or not? Human Psychopharmacology, 24; 199-205. [PubMed abstract]

Photo credits

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