Alcohol and pain in the population – BodyInMind – Comfortably numb – January 22, 2017
There is a problem in observational epidemiology. If a disease has an association with a behaviour within the population, we cannot tell which of these is true:
- the behaviour causes the disease;
- the disease causes the behaviour; or
- a third factor causes both.
The first instinct for the reader of an epidemiological study is often to infer that the behaviour causes the disease with which it is associated.
This is what gives rise to newspaper headlines warning of everyday items that cause or cure cancer.
A second instinctual and opposite reaction is to recite the response ‘correlation is not causation’ and to dismiss the result.
Both of these responses however would be wrong. There is always some causal relationship (that is a ‘reason’) behind an association and it is our job as researchers to try to determine exactly what the causal relationship is.
One such result from observational epidemiology that we and others have found is that those who drink alcohol are less likely to report chronic pain.
Furthermore, among those who do have chronic pain, those who drink alcohol are less disabled by the pain, have less severe symptoms and better quality of life.
The newspaper headline response to these findings might be ‘Alcohol helps cut disability caused by chronic pain’
more sceptical response would be ‘correlation is not causation’, and that this is a spurious and ridiculous finding.
Our response was rather, “Well, if we can’t necessarily conclude that alcohol is preventing people from reporting pain, what is the causal relationship behind these findings?”
To that end, we looked at the drinking habits and pain reporting in data collected from the UK Biobank
The UK Biobank is a large (over ½ a million participants) repository of data, including self-report data on a wide range of behaviours including diet, smoking, activity, and alcohol consumption, and both self-report and medical record data on disease outcomes
We were particularly interested in those people who had chronic pain all over the body. We were then able to look at whether people who drank less were more likely to report having chronic pain all over the body — and they were.
Apart from the problems of sampling error (which was overcome by having such a big sample) and measurement error (can people reliably report how much pain they have had? or how much alcohol?) there is a clear relationship between alcohol and pain.
What we wanted to know was:
could it be possible that those who did not drink were more likely to report pain because they had stopped drinking due to ill health?
We haven’t been able to show that alcohol helps people with pain or not.
My guess is that drinking alcohol is an indicator of good health – people drink to the extent that their health allows them, and they reduce their alcohol intake to the extent that they are prone to ill health and pain.
Again, here is the assumption that all pain is the same – and that could not be further from the truth.
No one is conducting studies comparing different kinds, types, or locations of pain, which leaves a wide gap in our knowledge about pain and its relief.
From personal past experience, I know that alcohol can ease some kinds of acute pain, but my chronic pain was always unaffected. Now that I’m taking opioids for my pain, I generally avoid drinking at all because it’s such a dangerous combination and only makes me sleepy.
So, if you know someone who is having problems with pain, it would definitely be unwise to advise them to have a drink – but if you know someone who avoids drinking altogether, it could be an idea to ask them if they have any problems with pain.
Author: Marcus Beasley
Marcus is a study coordinator with the Epidemiology Group at the University of Aberdeen in Scotland. His research interests include methodology in the epidemiology of chronic pain, particularly non-specific effects in trials of treatments for pain. He is currently working on recruitment for the MAmMOTH Study, a trial of CBT for the prevention of chronic widespread pain