Pain tolerance and pain perception in adolescents born extremely preterm

Neonatal pain experiences have been associated with altered processing and perception of pain in later life, but findings tend to vary among studies. We have compared experimental pain tolerance and subjective health complaints in a population-based cohort of adolescents born extremely preterm to that of matched term controls. Subjects performed a standardized cold pressor task (hand in ice water) and completed validated questionnaires regarding current subjective health complaints, including pain issues. Thirty-one (89%) of 35 eligible preterm subjects (mean gestational age 26.8 weeks) and 28 (80%) term controls participated in this follow-up study at mean age 17.8 years. Ten (32%) subjects born preterm versus 17 (61%) born at term reached the ceiling time of 180 seconds immersion time in the ice water, a hazard ratio for early withdrawal of 2.05 (95% confidence interval, 1.72 to 2.44), with males explaining most of the difference. For subjects born preterm, the risk of early withdrawal decreased significantly with more days of mechanical ventilation, more pain events, and more doses of morphine during the newborn period. Subjective pain ratings during the cold pressor task as well as health-related complaints and pain issues reported in the questionnaires were similar in the preterm and term groups.

Despite reduced tolerance to experimental pain, subjects born preterm scored their pain experiences similarly to those of term controls. Surprisingly, preterm subjects exposed to most painful and invasive neonatal experiences and also to most doses of morphine had a pain response at follow-up most closely resembling that of the control group.