Smokers and former smokers are more sensitive to pain than non-smokers, according to conclusions drawn from the Norwegian Tromsø Study and presented at the Congress of the European Pain Federation EFIC in Florence, Italy. "Until now, research into nicotine and pain has produced conflicting results. Some experimental studies have shown that smoking cigarettes and nicotine lessened sensitivity to pain, while observational studies have revealed that smokers were at higher risk of acute and chronic pain. Our aim was to investigate the association between smoker status and pain sensitivity," explained study author Dr Aslak Johansen of the University Hospital of North Norway, Tromsø.

10,364 people participated in the study. 22.1% of the women and 18.8% of the men who took part were smokers, while 38.6% of the women and 46.8% of the men were former smokers. Pain tolerance was assessed by the cold pressor test, using cold water.

"The smokers had the lowest tolerance to pain induced by cold water, followed by the former smokers, and men and women who had never smoked had the highest pain tolerance," Dr Johansen reported. "These results suggest that nicotine consumption leads to a long-term hyperalgesic effect."

Smoking, depression and pain

The connection between smoking status, chronic pain and depression has been analysed in a Scottish study that was also presented at the EFIC Congress. "Many studies show that the proportion of smokers is higher among chronic pain patients than in the general population, and that smokers report greater pain intensity and higher degrees of disability," said Dr Oliver van Hecke of the University of Dundee in the United Kingdom, one of the authors of the study. "Evidence from pain clinics indicates that depression could play a role in the link between smoking and chronic pain. We have now investigated this using data from a large population-based study," he explained.

The analysis centred on data from Generation Scotland: the Scottish Family Health Study. Of the 24,042 participants in the study, 36% indicated that they suffered from some form of chronic pain. "Chronic pain patients who smoke experienced greater average pain intensity as compared to non-smokers and former smokers, as well as a higher average level of pain disability," Dr van Hecke confirmed. "Specifically, it is the relationship between smoking and a history of major depression that contributes significantly to the effect of smoking on pain intensity, but not to smoking-related pain disability within this general population-based cohort ", he added.