A new study links short-term nicotine abstinence to greater pain sensitivity and higher postoperative analgesic needs, driven by altered activity in specific brain regions.

Summary
Researchers found that smokers who abstained before surgery experienced stronger pain and used more postoperative pain medication—especially opioids—than nonsmokers. The increase in pain sensitivity grew with longer abstinence but appeared confined to a limited window, consistent with previous evidence that pain responses may normalize after about three months. Mapping brain activity revealed distinct neural networks tied to heightened pain processing and to the increased need for postoperative care.

Key findings
– Higher pain sensitivity: Abstinent smokers had lower pain thresholds and required more postoperative analgesics than nonsmokers.
– Brain activity changes: Resting-state fMRI showed reduced fractional amplitude of low-frequency fluctuations (fALFF) in the ventromedial prefrontal cortex (vmPFC), increased regional homogeneity (ReHo) in the left middle occipital gyrus, and decreased functional connectivity (FC) between the vmPFC and both the bilateral middle temporal gyrus and precuneus.
– Time dependence: Pain sensitivity increased with the length of abstinence but tended to normalize after roughly three months.
– Distinct networks: Different sets of brain regions were associated with pain sensitivity versus withdrawal-related postoperative care needs.
– Mediation effects: Preoperative pain threshold correlated positively with abstinence duration and specific regional brain activity/connectivity. The link between abstinence time and pain threshold was mediated by calcarine and posterior cingulate cortex activity. Dysfunction in the vmPFC and left anterior cingulate cortex (ACC) fully mediated the relationship between withdrawal symptoms and postoperative analgesic requirements.

Study details
The prospective cohort study enrolled 60 male patients undergoing partial hepatectomy: 30 abstinent smokers and 30 nonsmokers. Investigators collected clinical data, smoking histories, pain measures, and resting-state fMRI scans. Compared with nonsmokers, the abstinent group showed lower pain thresholds, greater postoperative analgesic use, and specific alterations in brain functional measures (fALFF, ReHo, and FC).

Interpretation and implications
The findings suggest nicotine withdrawal can alter supraspinal brain function and contribute to hyperalgesia in abstinent smokers, helping explain why these patients may need more pain relief after surgery. Because the effect appears time-limited, the results do not mean smokers should avoid quitting before surgery. Rather, the authors emphasize the need to understand and manage short-term withdrawal-related pain to reduce reliance on opioids.

Research directions
The team is already investigating a postoperative analgesic that might work better than opioids for abstinent smokers, and they are studying the mechanisms and effectiveness of preoperative nicotine replacement therapies.

Quote
“We’d like to emphasize that our study does not discourage smokers from quitting before surgery,” said Kai Wei. “Our aim is to encourage researchers to delve deeper into the mechanisms underlying elevated pain sensitivity during short-term abstinence, with the goal of developing strategies to mitigate the clinical challenge of increased analgesic (especially opioid) use associated with preoperative smoking cessation.”

Source
Study published in the Journal of Neuroscience: “Altered Regional Brain Activity Underlying the Higher Postoperative Analgesic Requirements in Abstinent Smokers: A Prospective Cohort Study” by Zhijie Lu et al. Reported by SfN Media.

This article was adapted from an original report published on neurosciencenews.com. All rights belong to the original publisher.