Obesity and Daily Pain Linked, Study Finds

Allison Shelley

February 07, 2012

February 6, 2012 — A million-person Gallup poll has identified a clear association between excess weight and pain.

"We observed a very systematic relationship between body mass index categorizations and pain," lead investigator Arthur Stone, PhD, from Stony Brook University in New York told Medscape Medical News.

Dr. Arthur Stone

"The pain that obese individuals reported was not driven exclusively by musculoskeletal pain," Dr. Stone said. "This suggests other mechanisms for the relationship."

The results are published online in the January 19 issue of Obesity.

Recent small-scale studies have shown a positive association between obesity and self-reported pain levels. This study replicated those findings in more than a million randomly selected Americans who participated in telephone interviews.

Survey questions included height and weight, queries about pain conditions in the past year, and pain experience yesterday. "We measured pain on a daily basis in an effort to eliminate any biases of long-term recall of pain," Dr. Stone said.

Overweight respondents were further classified into 1 of 3 obesity levels as defined by the World Health Organization.

The researchers found that body mass and pain yesterday were reliably associated when demographic variables were controlled. The correlation held for both men and women and it became stronger in older age groups.

Table. Logistic Regression of Body Mass Index Predicting Pain Yesterday

Body Mass Classification Adjusted (%) Adjusted Odds Ratio (95% Confidence Interval)
Low-normal (<25) 18.9 1.00
Overweight (25 - <30) 21.8 1.20 (1.19 -1.22)
Obese I (30 - <35) 27.7 1.68 (1.65 - 1.71)
Obese II (35 - <40) 34.7 2.36 (2.29 - 2.42)
Obese III (≥40) 44.1 3.54 (3.43 - 3.66)

"We wanted to explore this relationship further by checking to see if pain was due to diseases that cause reduced activity, which prompts increased weight" coinvestigator Joan Broderick, PhD, also at Stony Brook University, said in a news release.

Dr. Joan Broderick

"We found that pain yesterday was definitely more common among people with diseases that cause bodily pain," she noted. "Even so, when we controlled for these specific diseases, the weight–pain relationship held up. This finding suggests that obesity alone may cause pain, aside from the presence of painful diseases."

Dr. Stone speculated on several possible explanations. Some reports implicate leptin and other hormones associated with excess fat in complex physiological processes involving inflammation that can lead to painful conditions.

This theory suggests that having excess fat leads to physiological events that ultimately create states that result in pain. Therefore, the development of various pain conditions could be yet another outcome of weight gain.

These inflammation-based conditions could be in addition to the musculoskeletal disorders caused by the negative mechanical effects of excessive weight on joints, he explained.

Depression, obesity, and chronic conditions with pain have strong genetic influences. There is a well-known association between pain and depression, and it is possible that depression is an important factor in the weight–pain relationship, Dr. Stone pointed out.

"Psychosocial and environmental factors are likely powerful contributors to the relationship. For example, there may be a circular relationship in medical conditions that are linked to both pain and weight gain. For people with arthritis, the pain may discourage physical activities that can help to maintain normal weight," the researchers write. As pain increases, inactivity can result in weight gain.

The investigators suggest that the study findings support the importance of metabolic investigations into the causes of pain. "In the meantime," Dr. Stone said, "clinicians should continue encouraging weight loss to reduce pressure on joints, ease pain, and lower the risk of diabetes and other comorbidities."

Dr. Stone is a senior scientist with the Gallup Organization, a senior consultant with PRO Consulting, and a member of the Scientific Advisory Board of Wellness and Prevention Inc. Dr. Broderick is the spouse of Dr. Stone and shares his financial disclosures.

Obesity. Published online January 19, 2012. Abstract.

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