Chronic pain and high blood pressure are highly prevalent among US adults, with one fifth of the population experiencing daily pain and nearly half having hypertension. A new study suggests the two conditions may be connected.

The study, which was published in Hypertension, shows chronic pain may increase the risk for hypertension, independent of multiple confounders. These variables include age, sex, lifestyle factors such as smoking and alcohol use, blood markers such as cholesterol and glucose levels, and use of certain medications such as statins or insulin.

“Previous studies have largely focused on the connections between acute pain and hypertension,” senior author Jill P. Pell, CBE, former director of the School of Health & Wellbeing and the Henry Mechan Professor of Public Health at the University of Glasgow in Glasgow, Scotland, told Medscape Medical News. “Studies of chronic pain and hypertension have been few and have produced inconsistent results.”

Pell and colleagues analyzed the impact of chronic pain on nearly 207,000 adult volunteer participants in the UK Biobank, a large health data bank. The mean age of the participants was 53.84 years, 61.7% were women, and nearly all (96.7%) were White. At baseline, about 40% reported no pain, while over 40% reported chronic localized pain at one to seven body sites. More than 2300 participants (1.1%) said they lived with chronic widespread pain.

When the investigators matched baseline pain status with blood pressure after a median follow-up of 13.5 years, they found an independent association between hypertension and chronic pain. Key findings included:

• 19,911 (9.62%) of all participants developed hypertension.
• After adjustment for confounders, hazard ratios for developing hypertension were 1.10 for short-term pain (95% CI, 1.03-1.17), 1.20 for chronic localized pain (95% CI, 1.14-1.26), and 1.75 for chronic widespread pain (95% CI, 1.52-2.00) when compared with no pain.
• Hypertension rates were the highest for people with severe pain and pain affecting multiple body systems. Dose-response relationships were found in terms of the number of body sites affected by chronic pain and chronic musculoskeletal pain.

Pain and Hypertension: The Chicken or the Egg?

Does having pain trigger hypertension, or does hypertension have the potential to cause pain? Both may be true, according to pain specialist Steven P. Cohen, MD, chair of anesthesiology and vice chair of pain medicine at the Northwestern University Feinberg School of Medicine in Chicago.

In patients with peripheral vascular disease, ischemia can be a source of nociceptive pain due to tissue injury or neuropathic pain due to nerve injury.

“Some forms of chronic pain can activate the sympathetic nervous system causing a ‘fight or flight’ response that may increase blood pressure,” Cohen told Medscape Medical News. “Independently, hypertension is associated with sleep disorders, depression, and other psychiatric conditions, which have bidirectional relationships with chronic pain.”

The study by Pell and colleagues suggests clinical depression in patients with pain may be a significant contributing factor in the development of hypertension. Adults with chronic pain have a prevalence of depression nearing 40%. Depression appears to be a key mediator of the connection between pain and hypertension, Pell noted.

“We found that 11.7% of this association was mediated by depression,” she said.

Practical Steps

“Given the bidirectional relationship between hypertension and chronic pain, and the intersectionality with other conditions such as sleep disorders and depression, I agree with the old adage that pain should be considered the fifth vital sign,” said Cohen, who is president of the American Society of Regional Anesthesia and Pain Medicine. “Hence, we should screen for pain as we do for body temperature, blood pressure, breathing, and heart rate.”

While screening for pain is standard in many medical settings, screening methods lack specificity, according to Cohen. “Our current standard for measuring pain is highly subjective: on a 0-10 scale, how much does it hurt?” he said.

In an effort to address this issue, Cohen is leading a research effort funded by the Advanced Research Projects Agency for Health to identify biomarkers for objectively quantifying pain in women. The study will look at more than 30 biomarkers, including stress hormones and inflammatory markers in interstitial fluid, as well as stress responses such as heart rate, galvanic skin response, and breathing.

“This is the first attempt to create a composite panel of markers to generate a quantitative score for pain,” Cohen said.

Pell reported having no conflicts of interest. Cohen reported receiving grant/research/clinical trial support from Avanos and consultant/advisory board payment from Avanos, Persica, SPR Therapeutics, Sword Health, and Vertex.