Could someone with more familiarity in reading scientific papers tell me if the paper shows any material difference in the types of Bluetooth headphones tested (in-ear, over-head, neckband)?

It's shown in some of the figures, but all I found in the discussion section was: "Given the thyroid's high sensitivity to radiation, long-term exposure to NIR, especially from Bluetooth headphones worn close to the neck, might intensify the impact on this organ."

I've got a small Bluetooth receiver with a 3.5mm aux port that I'm planning on using with my wired over-head headphones, but my initial plan was mounting the receiver onto the headset itself. Maybe it would be better to keep it further away.

Or perhaps it doesn't really matter and time is the most important factor that I can control for (Figure 7).

Conclusion

This investigation delved into the correlation between thyroid nodules and the use of Bluetooth headphones, elucidating the potential implications of NIR in daily life, particularly its impact on thyroid health. The findings suggest that besides age, a known factor, prolonged and frequent use of Bluetooth headphones may be associated with an increased risk of developing thyroid nodules, potentially linked to the cumulative effects of NIR emitted by the headphones on the thyroid gland. Moreover, this study underscores the necessity of giving special attention to thyroid health while assessing the health risks of modern wireless technologies. Although this research offers valuable insights, its limitations preclude direct inferences of causality. Future research should further investigate the specific relationship between long-term use of Bluetooth headphones and the risk of thyroid nodules, and develop more precise preventive measures to mitigate the potential health risks posed by NIR. Additionally, the findings of this study provide crucial guidance for public health policymakers, aiding in the promotion of modern technology while simultaneously enhancing public awareness and prevention of its potential health impacts.

This makes no sense to me. Bluetooth headphones are mostly a receiver and transmit very little. I am very skeptical about these findings.

I use Bluetooth earbuds almost all day.