Dr. Christopher Sivert Nielsen is a Research Professor Norwegian Institute of Public Health, and holds additional positions at the Department of Pain Management and Research at Oslo University Hospital and at the Department of Community Medicine at UiT –The Arctic University of Norway. 

Dr. Nielsen is a clinical psychologist and epidemiologist specializing in the study of pain and related human characteristics. Dr. Nielsen has published extensively from Norwegian Twin Registry and was among the first to demonstrate that experimental pain sensitivity is heritable. Further studies have focused on genetic and environmental relationships between pain and psychological traits. He leads the Tromsø Pain Study, the largest experimental pain study worldwide with more than 30.000 examinations completed. The study size, high response rate (65%), wide age range (30-99) and availability of eight-year longitudinal follow-up data, make this a unique platform for studying clinical and experimental pain in the general population. The study has yielded new insight into the relationship between pain sensitivity and chronic pain conditions; provided evidence that both opioid and non-opioid analgesic use are associated with hyperalgesia; demonstrated that pain inhibitory mechanisms vary across sex and clinical pain status; and documented that pain tolerance is associated with low-grade systemic inflammation.