Does smoking make MS cognitive symptoms worse?

Summary

About half of all people with MS have problems at some time with aspects of thinking such as memory, concentration or problem solving. Cognition is the term that covers all aspects of thinking and so these symptoms are referred to as cognitive problems.

Previous research has implicated smoking as a trigger for MS, as well as suggesting it can increase the number of relapses and increase disability progression. Despite the evidence for its role in influencing the course of MS, the effect of cigarette smoking on cognition has not been investigated.

72 people with MS from Turkey took part in the study. Participants were asked about their smoking habits and their cognitive function was assessed using the Brief Repeatable Battery of Neuropsychological Tests (BRB-N). These tests assess memory, attention, language function and how well the person can process information.

The study found that there were 24 non-smokers in the group and 20 heavy smokers. When the researchers compared the test scores it was found that although some of the non-smokers had cognitive problems, more of the heavy smokers had cognitive difficulties and their problems with memory and information processing were significantly worse.

The study shows that heavy smoking appeared to be related to cognitive difficulties in people with MS. The authors conclude that this study is the first to investigate the effect of smoking on cognition in people with MS, but it fits in with previous research that has shown that smoking can also make other MS symptoms worse.

Background

About half of all people with MS have problems at some time with aspects of thinking such as memory, concentration or problem solving. Cognition is the term that covers all aspects of thinking and so these symptoms are referred to as cognitive problems.

Previous research has implicated smoking as a trigger for MS, as well as suggesting it can increase the number of relapses and increase disability progression. Despite the evidence for its role in influencing the course of MS, the effect of cigarette smoking on cognition has not been investigated.

How this study was carried out

72 people with MS from Turkey took part in the study. 80% had relapsing remitting MS, 14% had secondary progressive MS and 6% primary progressive MS. The average age was 35.5 years old, on average the participants had MS for 6.5 years and the average EDSS score was 1.5 although this ranged from 1-7.5.

Participants were asked about their smoking habits and the researchers calculated how much they smoked, using the 'pack year' calculation. This is calculated by multiplying the number of packs of 20 cigarettes smoked each day by the number of years the person has smoked, therefore one pack year is the equivalent to smoking a pack of 20 cigarettes every day for one year. The researchers considered participants were heavy smokers if they had smoked for at least 10 pack years (equivalent to 20 cigarettes a day for 10 years) and were still smoking.

Cognitive function was assessed using the Brief Repeatable Battery of Neuropsychological Tests (BRB-N). These tests assess memory, attention, language function and how well the person can process information.

What was found

The study found that there were 24 non-smokers in the group, 20 heavy smokers and the remaining 28 were either ex-smokers or light smokers. The non-smokers were more likely to be women (15 out of 24) and the heavy smokers more likely to be men (13 out of 20), but both groups EDSS scores, number of years in education and number of years since MS diagnosis were all very similar.

When the researchers compared the test scores it was found that heavy smokers were more likely to have cognitive difficulties and they also had significantly greater difficulties than non-smokers. The heavy smokers had the greatest problems with working memory (short term storing and manipulating pieces of information) and how well they could process information.

What does it mean?

The study shows that heavy smoking appeared to be related to cognitive difficulties in people with MS. Although non-smokers did have cognitive problems, more of the heavy smokers had difficulties and their problems with memory and information processing were significantly worse.

The authors conclude that this study is the first to investigate the effect of smoking on cognition in people with MS, but it fits in with previous research that has shown that smoking can also make other MS symptoms worse.