If you’re involved in a car crash and are overweight or obese then your risk of persistent neck pain is higher than for someone who is not overweight, according to a new study presented at the 63rd Annual Scientific Meeting of the American Pain Society (APS).
The results of this study showed that the risk of neck pain lasting at least six months after an accident almost doubles if the person is morbidly obese, so what is it that makes those who are overweight more vulnerable to chronic pain?
This latest study was presented by Ana L. Bermudez, MD, from the Department of Anesthesiology, University of North Carolina, Chapel Hill, and detailed the results of almost a thousand patients admitted to the emergency department after a traffic collision. The patients were all aged 18 to 6 yeas old and were seen at the ED within 24 hours of their accident. The patients were categorised according to their BMI with 37% having a normal body mass index (18.5 to 24.9 kg/m2), 32% classed as overweight (25.0 to 29.9 kg/m2), 18% obese (30.0 to 34.5 kg/m2) and 13% morbidly obese (=35.0 kg/m2).
What the researchers found was that the risk of persistent neck pain and overall pain connected to whiplash significantly increased in line with the patients’ BMI with pain lasting as long as a year in those who were overweight or obese. To determine levels of pain the patients were assessed for neck pain, shoulder pain (bilateral and unilateral), and upper and lower back pain. This was done in-person in the ED and by telephone six months later and twelve months after the accident. The patients rated their pain on a scale of 1-10 and a score over 4 was deemed moderate to severe pain.
Neck Pain Persists in Obesity
The relative risk of moderate to severe axial pain at the six month mark was 1.2 for those who were overweight, 1.4 for those who were obese, and 1.9 for those who were morbidly obese. Those with a normal BMI and those who were overweight had a similar risk of pain a year after their accident but the risk was increased by 20% and 40% respectively for those who were obese and morbidly obese. For some, the risk of persistent neck pain a year later more than doubled (RR 2.4).
Overall pain scores showed a similar association with increasing BMI with the relative risk at six months being 1.1, 1.3, and 1.7 for those who were overweight, obese, and morbidly obese respectively. A year after their car crash these scores were 1.0, 1.3 and 1.4. Again, for some morbidly obese patients the relative risk of pain doubled.
Why Obesity Increases Neck Pain Risk
This study only shows an associated between increased BMI and persistent neck pain and overall pain after a car crash but the mechanisms behind such an increased risk may include:
- Increased inflammation courtesy of pro-inflammatory cytokines produced by adipose tissue
- Decreased capacity to engage in physical therapy for whiplash pain
- Poor blood sugar regulation and increased systemic inflammation
- Increased pressure on joints in the neck and back from greater body weight.
It is also possible that those who are already obese or overweight at the time of a car crash are predisposed to higher levels of pain and persistent neck pain by dint of an existing pain condition or mobility issue. Decreased overall health, a sedentary lifestyle, and factors that contribute to metabolic disorders also increase the likelihood of chronic pain and poorer recovery from trauma.
People who are overweight or obese may even have difficulty maintaining a safe driving posture, meaning that should they be involved in an accident their head may be thrown forwards and backwards to a greater degree than someone who is able to sit with their head flush against the headrest of the seat. As such, maintaining a healthy body weight appears to reduce the risk of experiencing ongoing neck pain connected to whiplash in addition to having a number of other health benefits.
American Pain Society (APS) 33rd Annual Scientific Meeting. Abstract 235. Presented May 1, 2014.