Abdominal Fat Linked to Chronic Musculoskeletal Pain, Particularly in Women

Zemene Demelash Kifle, PhD candidate

Credit: LinkedIn

A new study shows abdominal adipose tissue is linked to chronic musculoskeletal pain, especially if there are excess fat deposits at multiple body sites.^1,2

“This study found a dose-response association between abdominal [visceral adipose tissue], [subcutaneous adipose tissue], [visceral adipose tissue/ subcutaneous adipose tissue] ratio and BMI with the number of chronic pain sites in both sexes,” wrote investigators, led by Zemene Demelash Kifle, PhD candidate, from the University of Tasmania Menzies Institute for Medical Research at Hobart in Australia.

Obesity is known to be associated with musculoskeletal pain, but until now, no studies examined whether excess fat in the visceral or subcutaneous adipose tissue is associated with musculoskeletal pain. This study identified a sex difference in the relationship between adipose tissue and chronic musculoskeletal pain.

Investigators sought to assess the association between abdominal adipose tissue and widespread chronic musculoskeletal pain. For their observational study, they leveraged data from the UK biobank. Participants were registered with the UK National Health Service and lived within 25 miles from 1 of 22 assessment centers in England, Wales, or Scotland. In total, investigators included 32,409 participants, with 50.8% women and a mean age of 55 ±7.4 years.

Participants had abdominal MRI scans at 2 imagining visits, 2.7 years apart, to quantify body fat. Additionally, they completed touchscreen evaluations to assess pain in their neck, shoulder, back, hip, knee, or “all over the body” and had to answer if pain interfered with their regular activities. If participants answered “all over the body” they were asked if the pain lasted ≥ 3 months, which would indicate chronic pain.

Based on their responses, participants were categorized into 6 groups based on chronic pain numbers: no chronic pain, 1 chronic pain site, 2, 3, 4, and those with chronic pain all over. Participants were also categorized as having chronic pain or not.

Covariates were also considered in the analysis; these included age, household income, highest education qualification, ethnicity, standing height measured with the Seca 202 device, physical activity, alcohol consumption, smoking status, comorbidities, psychological problems, and sleep duration.

The multivariable analysis showed a dose-response association of visceral adipose tissue, subcutaneous adipose tissue, and their ratio with the number of chronic pain sites for both women and men.

Women:

• Visceral adipose tissue: odds ratio [OR], 2.04 per SD; 95% confidence interval [CI], 1.85 to 2.26)
• Subcutaneous adipose tissue: OR, 1.60; 95% CI 1.50 to 1.70
• Ratio: OR, 1.60; 95% CI 1.37 to 1.87

Men:

• Visceral adipose tissue: OR, 1.34; 95% CI 1.26 to 1.42
• Subcutaneous adipose tissue: OR, 1.39; 95% CI, 1.29 to 1.49
• Ratio: OR, 1.13; 95% CI 1.07 to 1.20

Investigators found greater levels of adipose tissue were linked to greater odds of reporting chronic pain in both sexes, and this was still the case after adjusting for covariates. However, women had a relatively larger effect estimate of these adipose measures, suggesting women had a stronger association between abdominal fat and widespread chronic pain.

“The observed sex differences in the effect estimates of adipose measures with number of chronic pain sites may be attributed to several mechanisms including the influence of sex hormones on adipose tissue distribution, function, and storage,” investigators wrote. “In women, [subcutaneous adipose tissue] tends to expand primarily through an increase in adipocyte size rather than by proliferating new cells. This could indicate that [subcutaneous adipose tissue] may not adequately expand to accommodate excess fat storage, resulting in the accumulation of fat in [visceral adipose tissue] or other ectopic depots.”

Investigators also added how adipocyte size plays an important role in regulating adipokine secretion. The larger the adipocyte, the increased secretion of proinflammatory adipokines. Additionally, research suggests women have a stronger inflammatory response than men, which could explain the sex differences in pain.

Investigators highlighted several limitations, including the pain questionnaire not assessing pain severity, the MRI was only conducted on 2 occasions, potential unmeasured confounders, a relatively small—and White—imaging sample, and only having 2 brief screening questions to evaluate for psychological issues.

“Abdominal adipose tissue was associated with chronic musculoskeletal pain, suggesting that excessive and ectopic fat depositions may be involved in the pathogenesis of multisite and widespread chronic musculoskeletal pain,” investigators concluded. “The identified stronger effects in women than men may reflect sex differences in fat distribution and hormones.”

References

1. ^{Kifle ZD, Tian J, Aitken D, et al. Reg Anesth Pain Med Epub ahead of print: [10 September, 2024] doi:10.1136/rapm-2024105535}
2. ^{Abdominal fat linked to widespread chronic pain, especially in women. EurekAlert! September 10, 2024. https://www.eurekalert.org/news-releases/1057103?. Accessed September 10, 2024.}