Occupational exposure to solvents may have lasting effects on brain health

Researchers in France and the US have found that high occupational exposure to solvents is linked to poorer cognition in retirement.

Posted on 12th May 2014

Researchers in France and the US have completed a study of 2,143 retired French utility workers and found that high occupational exposure to solvents was linked to poorer cognition in retirement. The study is published on 12 May in the journal Neurology.

Occupational exposure to organic solvents such as paints, degreasers, adhesives and glues has been associated with health problems, with studies suggesting they may affect memory and thinking skills. To investigate potential long-term effects of occupational solvent exposure on cognition, a team of researchers studied 2,143 retired male French civil servants. All had been previously employed at the national utility company, Electricite de France-Gaz de France (EDF-GDF). The average age of volunteers was 66, and the average time since retirement was 10 years.

In 2010, the volunteers underwent physical and cognitive examinations. These examinations included assessment of general cognitive ability, as well as those that tested more specific memory and thinking skills including memory for words, the ability to plan and organise, and the ability to coordinate vision with movement.

Using the full job histories of the volunteers, available through company records, the researchers were able to create a ‘job-exposure matrix’ which estimates the lifetime exposure to inhaled organic solvents based on job description. These solvents included petroleum solvents and benzene. The team used this information to estimate the yearly exposure to solvents of each volunteer between 1960 and 1998.

Volunteers were categorised into groups of those never exposed, and those with moderate and high exposure. Those volunteers who were exposed to solvents as part of their job were also categorised by the date they were last in contact with the chemicals.

The results showed that those men who had a high lifetime exposure to solvents tended to score more poorly on the MMSE, a test of general memory and thinking skills. They were also more likely to perform less well on some, but not all, of the specific cognitive tests.

The poorest performing group on several different cognitive tests comprised volunteers who had experienced high exposure to solvents the most recently. Those volunteers who had moderate exposure to solvents consistently showed a lower risk of cognitive problems compared to those with high exposure.

The authors suggest the findings are of importance, particularly in industrialised countries with rising retirement ages. They suggest the need to consider how to support those retiring from jobs involving exposure to high levels of solvents, to maintain cognition as they get older.

Dr Simon Ridley, Head of Research at Alzheimer’s Research UK, the UK’s leading dementia research charity, said:

“These kinds of studies are helpful for identifying trends and highlighting possible risk factors for cognitive decline but it is always hard to discount other factors that might be at play. This study shows some strengths in terms of research design, using company records to estimate solvent exposure rather than rely on workers self-reporting using questionnaires, but the findings are not clear cut.

“The report reveals associations between high solvent exposure and poorer performance on some, but not all, memory and thinking tests, suggesting a potentially complex picture in need of further investigation. It is also unclear what effect this poorer performance had on a person’s day-to-day life and their long-term risk of dementia.

“While the study raises an important area for further research, it’s important to remember that volunteers in this study had long-term exposure to solvents through their work at much higher levels than the general population experience in everyday life.”

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