Thursday June 5 2008
Patients were asked about their drinking
Alcohol reduces the risk of arthritis, reports the Daily Mirror today. Scandinavian research has shown that a “regular tipple can cut the risk of developing arthritis by up to 50 per cent”, the newspaper says.
The story is based on studies of over 2,750 people, and looks specifically at rheumatoid arthritis, rather than the more common osteoarthritis. The limitations of the study design, and the fact that the mechanism by which drinking a moderate amount of alcohol exerts this potential protective effect is not yet fully understood means that it is too early to suggest alcohol as a treatment to prevent this disease. There are well-known dangers from drinking too much, and these certain risks probably outweigh any uncertain benefit for reducing the risk of rheumatoid arthritis.
Where did the story come from?
Dr Henrik Källberg of the Karolinska Institute in Stockholm led the research. Funding sources for the two separate data sources are declared in a supplement. The study was published online in the peer-reviewed medical journal: Annals of the Rheumatic Diseases.
What kind of scientific study was this?
This was an analysis of two separate case–control studies. One Swedish study, the Epidemiological Investigation of Rheumatoid Arthritis (EIRA), compared 1,419 people with newly rheumatoid arthritis (cases) with a matched control group without the disease, which was drawn from the general population. The second case–control study was from Denmark: the Case–Control Study on Rheumatoid Arthritis (CACORA) compared 515 people who already had rheumatoid arthritis (cases) with 769 controls, for an average of 2.3 years. Overall more than 2,750 people took part in the two separate studies, which assessed environmental and genetic risk factors for the disease.
In EIRA, a questionnaire was given to the patients shortly after they were informed about their diagnosis of rheumatoid arthritis. They were asked about alcohol, smoking and other environmental exposures. Similar data was obtained by posting questionnaires to the control group. Blood samples were also collected to check for genetic factors and antibodies to citrullinated peptide antigens (ACPA), which are a specific group of proteins involved in the development of the disease.
In CACORA the alcohol information was collected from both groups using a structured telephone interview.
The researchers quantified the average alcohol consumption in drinks per week, based on an average drink being equivalent to 16g of alcohol. Four categories were used: non-drinkers (12.5% of people in EIRA; 10.1% of those in CACORA); low consumption (consuming some alcohol, but less than the top half of the population); moderate consumption (consuming more than the bottom half of the population, but less than the top 25%); high consumption (among the top 25% of consumption).
The researchers used statistical methods to calculate the chances of developing or having rheumatoid arthritis in the four separate consumption groups, and also related this to those who had the ARPA antibody.
What were the results of the study?
Alcohol consumption was significantly more common in the control groups that did not have rheumatoid arthritis, and it was associated with a reduced risk of rheumatoid arthritis in both studies. The risk decreased as the alcohol consumption increased.
Among those who drank alcohol, the quarter with the highest consumption had a decreased risk of rheumatoid arthritis compared to the half with the lowest consumption, with a reduction of 40% in one study and 50% in the other. For the group of rheumatoid arthritis patients who had the ARPA antibodies, alcohol consumption reduced the risk most in smokers who carried a specific genetic variation.
What interpretations did the researchers draw from these results?
The researchers conclude that their findings of an association between increased alcohol intake and reduced risk of rheumatoid arthritis, along with “the recent demonstration of a preventive effect of alcohol in experimental arthritis, indicate that alcohol may protect against rheumatoid arthritis”. They suggest that the results emphasise the benefits of stopping smoking, but not necessarily to abstain from alcohol as a strategy to reduce the risk of developing this disease.
What does the NHS Knowledge Service make of this study?
These studies have been analysed and reported separately in the Annals of the Rheumatic Diseases. This is appropriate, because in one study the participants had new onset of rheumatoid arthritis, and in the other they had already developed the disease. In addition, the studies came from different countries and from populations in which the authors say there was a different average level of alcohol consumption (consumption was higher in Denmark). Other limitations acknowledged by the authors relate to the study design and the challenges of measuring lifestyle factors by questionnaire:
- In ideal case–control studies, the control group is selected from a population that is as similar to the cases (those with rheumatoid arthritis) in as many other respects as possible. For example, they should be of similar age and sex, and drop out rates from the study should be similar in both arms. This allows for a reasonable comparison of the two groups. The controls in the CACORA group were more likely to be women and less likely to have smoked than the people with rheumatoid arthritis. In the EIRA study the controls were also less likely to have smoked than the people with rheumatoid arthritis.
- The researchers also suggest that people with rheumatoid arthritis may have been advised to abstain from alcohol by their doctors (because of the medication they take) and this could introduce a bias into the results. However, in reality, there was a similar amount of alcohol consumed among people taking medication.
The exact mechanism by which drinking a moderate amount of alcohol exerts this potential protective effect is not yet fully understood. There is a danger that these results might be interpreted as a suggestion that increasing alcohol intake among non-drinkers is a reasonable choice if they want to prevent the development of arthritis. However, there are also well-known dangers from drinking too much, and these certain risks probably outweigh any uncertain benefit for reducing the risk of rheumatoid arthritis.
Sir Muir Gray adds...
This is not evidence to start drinking alcohol to reduce the risk of arthritis, but encouraging news for those who enjoy one or two drinks a day.