Assessing the reliability of an infrared thermography protocol to assess cold-induced Brown Adipose Tissue activation in French psychology students

The authors use infrared thermography measurements of skin temperature to non-invasively assess the heat production of Brown Adipose Tissue (BAT). In species other than humans, BAT has been linked to maternal care, and may thus be crucial for understanding differences in attachment security. Whereas early BAT research measured its relative presence in the human body through radioactive tracers, infrared thermography measurement of skin temperature in cold conditions has recently been proposed as an evaluation of BAT thermogenesis. Infrared thermography relies on comparing skin temperature in the supraclavicular region, (where a BAT depot is located), with skin temperature in the sternal region (which contains no BAT depots). In cold conditions, the supraclavicular BAT depot produces heat, potentially allowing an assessment of the presence of BAT. We replicated an infrared thermography protocol, which previously reported an increase of 0.2 °C in supraclavicular (vs. sternal) skin temperature in cold (vs. control) conditions in only 7 adults, which probably led to overestimating the effect. With a much larger sample size (N=94 young adults) and the same protocol, we did not find any significant variation in relative (Cohen's d=0.10, 95%CI = [-0.31, 0.50]) or absolute supraclavicular skin temperature (Cohen’s d=0.11, 95%CI = [-0.30, 0.52]). Using conditional random forests, we also excluded a variety of alternative explanations for why the method failed to achieve an effect. Infrared thermographic measurements of skin temperature obtained with this protocol cannot measure BAT thermogenesis.