Aging comes with a lot of changes in the human body – cells weaken and break down faster, bones become weaker, and standing for hours becomes difficult. For some people, standing straight becomes a problem too, and a higher population experience lower back pains. Lower back pain is a very common reason for visits to the doctor. This is because one of the changes in the human body that occurs as one gets older is a reduction in the fluid content between the vertebrae. This causes contact between the vertebrae, thereby resulting in pain.
Generally, pain can be acute or chronic. Acute pain lasts anywhere from a few days to a few weeks. Acute pain becomes chronic when it lasts for three to six months, though, how and why acute pain develops into chronic pain is still not certain. It has been found that in patients with chronic lower back pain (CLBP), there is a change in how the central nervous system processes the pain in a way that alters the autonomic nervous system (ANS) balance. It is believed that this change is the reason the pain persists. Studies have been carried out to find out why this change occurs, and how to stop it and restore the normal ANS balance.
Non-invasive brain stimulation vs ANS balance
Researchers have been on the move to uncover the reason for the imbalance in ANS during chronic pain occurrence. It is believed that discovering this would make it easier for doctors to treat chronic pain effectively. Since the brain is the control-house of the human body, every stimulus, including pain, entering the body, reaches the brain and its intensity is determined by the activities that go on in the brain after reaching it.
During the research, it was discovered that during the occurrence of chronic pain, the activity of the central nervous system affects the balance of the ANS outside its normal levels during pain processing. To restore this balance, a randomized, double-blind, crossover, sham-controlled study was done to determine whether the use of transcranial alternating current stimulation (a form of non-invasive brain stimulation) would be effective.
ANS metrics from a previously published study of transcranial alternating current stimulation (tACS) were used. The ANS metrics include heart rate variability (HRV) and respiratory sinus arrhythmia (RSA). HRV reflected the balance of both parasympathetic and sympathetic ANS actions, while RSA reflected the balance of parasympathetic ANS action only. The study examined the outcome of 10Hz-tACS on both ANS balance metrics as calculated from electrocardiogram (ECG). Observations were taken 2mins before and after 40mins of 10Hz-tACS.
At the end of the study, there were no observable changes in both metrics. However, exploratory analyses on time-domain HRV showed a reasonable increase in the standard deviation of normal intervals between R-peaks (SDNN), another metric of ANS balance with sham.
Although the non-invasive stimulation technique used had no significant effect on RSA, exploratory analysis on HRV revealed that ANS can be regulated by tACS. This means that the balance can be restored, and CLBP can be reduced. These findings would help for the innovation of better treatment procedures for CLBP, and a consequent reduction in the potential disabled population it can cause.
Chronic lower back pain has remained a common cause of a visit to the doctor, especially among the older population. It is also known to be the second most prevalent cause of disability in adults. This study provides a means for more effective treatment options to be discovered.
Targeting the Autonomic Nervous System Balance in Patients with Chronic Low Back Pain using Transcranial Alternating Current Stimulation: A Randomized, Crossover, Double-Blind, Placebo-Controlled Pilot Study