Pain initiates a stress response that increases sympathetic output and leads to autonomic imbalance. Heart rate variability (HRV) is a easy to perform, valid measure of autonomic function. HRV biofeedback (HRV-B) is a novel biobehavioral procedure in which patients learn to restore autonomic balance by developing 'HRV Coherence'. Patients in HRV Coherence have improved mood and cognition. The investigators' pilot study showed that HRV-B alleviated chronic pain and stress among Veteran Pain Clinic patients. HRV-B thus has a pivotal role in managing pain. The proposed project is a randomized, sham-controlled, biobehavioral intervention with HRV-B to test the hypotheses that HRV-B increases HRV coherence and reduces pain, stress, fatigue, insomnia and depression and improves sleep, activity, and cognition in Veterans with chronic neuromuscular pain. The investigators hypothesize that HRV-B will (1) reduce self-reported pain and stress ratings, (2) improve objective measures of actigraphic sleep parameters (sleep latency, duration, efficiency, fragmentation), rest/activity rhythms (dichotomy index, interdaily stability) and cognitive function (reaction time, attention); and (3) alleviate self-reported fatigue and depression symptoms. Patients from two groups will be randomized to the investigators' previously established HRV-B or sham protocol (n=40 each), and will complete a baseline assessment, 6 weekly training sessions, a post-training assessment, and 4-week and 8-week follow-up evaluations post-training. Portable, hand-held, data-logging devices will be used to practice attaining HRV coherence at home by the active HRV-B training group, while those in the sham training group will get a 'stress squeeze ball'. Standard methods will quantify HRV coherence and other HRV measures, and validated instruments will be used to assess pain, stress, fatigue, insomnia, depression, and cognitive function. Wrist actigraphy will be used to objectively characterize insomnia via continuous recordings collected 24-hrs/day over three 1-week periods (pre-training, post-training, and at the 4 week follow-up assessments. Tests measuring attention and reaction time will assess changes in cognitive performance. Data analyses will apply linear models for repeated measures to evaluate the effect of HRV-B on study outcomes, and on treatment persistence, after adjusting for confounding factors. This study will be the first to examine HRV-B for pain management among Veteran chronic pain patients.

This study fulfills the national Veterans Health Administration/Department of Defense (VHA/DoD) Task Force recommendation that complementary, integrative therapies for pain management be provided to Veterans. Chronic pain elicits stress which increases sympathetic output fostering autonomic nervous system imbalance, an overextended stress response, fatigue, depression and insomnia. Heart Rate Variability (HRV) is a measure of the interplay between the sympathetic and parasympathetic nervous systems, and thus is a useful and easily-measured index of autonomic balance that has a relationship to chronic pain effects. HRV biofeedback (HRV-B) is a novel, biobehavioral procedure that restores normal autonomic balance. Through HRV-B, patients increase parasympathetic cardiac output and restore autonomic balance via induction of 'HRV coherence'. The investigators' pilot study indicated that HRV-B produced coherence and alleviated self-reported ratings of chronic pain and stress among Veterans attending the investigators' Pain Clinic. The proposed clinical intervention will further test hypotheses that HRV-B increases HRV coherence, reduces self-reported pain, stress, depression, fatigue, and insomnia, and improves cognition among Veterans with chronic pain.

The specific aims are to: (1) conduct a randomized, sham-controlled, pilot intervention trial to determine whether HRV-B increases HRV coherence among chronic pain patients (n=40 each for the HRV-B and sham treatment groups; total N=80 patients); (2) determine whether HRV-B reduces self-reported pain and stress among chronic pain patients. The primary endpoints include HRV coherence, pain (Brief Pain Inventory or BPI),and stress (Perceived Stress Scale or PSS)

Outcomes will be measured at 4 time points. pre-training; post-training, one week after the 6 weekly treatments are over; at 4 weeks follow-up after post-training, and at an 8-week post-training follow-up (total time of participation is 16 weeks from pre-training to 8 week follow-up).

Furthermore, chronic stress is associated with disrupted circadian rest/activity rhythms and domains of quality of life (QoL) including fatigue, insomnia, and reduced physical and social functioning. Interventions that relieve pain thus represent a novel therapeutic target for normalizing dysfunctional rest/activity rhythms and these QoL domains among pain patients. The investigators are also interested in assessing the effects of HRV-B on cognitive function in pain patients. Thus, the investigators' secondary exploratory objectives are to determine if HRV-B: (1) improves sleep and rest/activity rhythms; (2) alleviates self-reported fatigue and depression; and (3) improves cognitive function (reaction time, attention). Circadian endpoints will be measured as actigraphic parameters of sleep (e.g., duration, efficiency), and rest/activity (e.g., dichotomy index, interdaily stability), and with the Insomnia Symptom Questionnaire (ISQ); fatigue will be assessed using the Multi-Dimensional Fatigue Inventory (MFI), which assesses general physical and mental fatigue and motivation. Depression will be assessed via the Beck Depression Inventory II (BDI-II). Cognitive function will be measured with a cognitive battery comprised of the Paced Auditory Serial Addition Test (PASAT), the Rey Auditory Verbal Learning Test (RAVLT), and the Psychomotor Vigilance Test (PVT).

Proposed Intervention. HRV-B training will follow a previously established, standardized protocol. The primary (HRV coherence, pain, stress) and exploratory outcomes (insomnia, fatigue, depression, cognition). Outcomes will be assessed at 4 time points: pre-training; post-training, one week after the 6 weekly treatments are over; at 4 weeks follow-up after post-training, and at an 8-week post-training follow-up (total time of participation is 16 weeks from pre-training to 8 week follow-up). There will be no HRV-B training at the 8 week follow-up, only assessment. Standardized procedures will characterize HRV coherence and other frequency- or time-domain HRV measures, and validated instruments will be used to assess pain and stress. Wrist actigraphy will characterize insomnia via continuous, 24-hour/day personal monitoring of rest/activity rhythms at 1-week intervals coinciding with the baseline pre-training (baseline), post-training, and 8-week follow-up assessments. The investigators will provide portable data-logging devices for practicing HRV-B at home. Sham intervention subjects will have pulse and respiration monitored but not receive active training; instead they will view a static, relaxing nature picture on a computer screen.

The investigators will control false discovery rates at 5%. Analyses will be based on intent to treat with two-sided tests. The effect of HRV-B on coherence and other HRV variables will be analyzed using linear mixed models for repeated measures data from sequential time assessments, and a between-subjects factor to evaluate the intervention after adjusting for potential confounding factors (e.g., age, standard therapy, medications, co-morbid disease). Baseline relationships between HRV and endpoints will be examined using multiple regression models. Few studies have examined the multivariate relationship between pain, autonomic dysfunction, stress, depression, sleep, rest/activity rhythms, fatigue, and cognition.

Inclusion Criteria:

• are a Veteran between age 18 or older
• have chronic, non-malignant, neuro-musculoskeletal pain

Exclusion Criteria:

• a history of arrhythmia requiring medication or hospitalization
• a pacemaker or automatic implantable cardioverter-defibrillator
• a history of ischemic heart disease, heart transplant, cardiovascular surgery within 1 year
• congestive heart failure
• uncontrolled hypertension
• an active prescription for certain heart medications
• a history of seizures or use of antiseizure or anticonvulsant medication
• moderate or severe head injury or stroke
• evidence of active substance abuse or dependence (alcohol or tobacco use is not be an exclusion, participants will be asked to provide information about these behaviors in the investigators' questionnaire)
• a history of bipolar, psychotic, panic or obsessive-compulsive disorder (note: depression is an exclusion)
• cognitive impairment (dementia), neurocognitive deficits, or a central nervous system or neurological disorder (e.g., Gulf War Syndrome)
• a current or pending worker compensation claim or personal injury litigation related to the participants' symptoms

The project duration was ~4.5 years. Audits were performed annually.

The study was a behavioral intervention and is therefore not amenable to blinding.