Investigations Into the Impact of Static Magnetic Fields on Blood Flow

Many claims are made regarding the impacts of static magnetic fields (SMFs) on biological and physiological processes. Some of these are based on scientific underpinnings, and others appear to have less evidence to support them. The present report focuses on the evidence regarding SMF's effects on blood flow. Fortuitously, the author has direct experimental experience in this area. The approach for this review was to search three major databases (Web of Science, PubMed, and Embase) for peer-reviewed articles written in English in which an SMF was used in humans or other animals and measurements of parameters related to blood flow or velocity before SMF application and either during or after application were reported. After screening the initial 1,954 articles, 108 studies were retrieved and evaluated for relevancy. Of these, 23 were found to satisfy the inclusion criteria and be relevant. This included 10 studies on humans and 13 studies on other animals. The methods employed in many of these studies are illustrated in this review to enhance understanding of the findings. With regard to human studies, none showed an increase in blood flow, and one showed a decrease in flow. With regard to the animal studies, one showed a transient post-exposure increase that was later explained as due to an actual reduction during SMF exposure. Four studies showed a decrease, four showed no change or difference from sham-exposed animals, and four reported an increase. Of these four, two were from the same author using a method that may not have reflected a blood flow change. Based on these findings, it is concluded that claims of an SMF providing an increase in blood flow or circulation are not supported by human studies and not well supported by animal studies. However, this does not close the door to a possible effect for at least four considerations or limitations that may have impacted the absence of a positive finding in human studies: (1) the number of subjects included is relatively small, which affects the study power; (2) the duration of the SMF application of most studies was relatively short; (3) most studies were done on healthy individuals; and (4) the SMF was delivered perpendicular to the body surface, so the effects of tangential field directions are unknown. Although these provisos may impact the detection of a possible SMF effect, they do not alter the current findings, as no reviewed human study has demonstrated a statistically significant increase in blood circulation attributable to an SMF. Thus, the clinical use of an SMF to improve blood circulation is not supported by experimental evidence.