September Is Pain Awareness Month

Are Basic Pain Mechanisms Different in Women than in Men?

That is a puzzling question pain researchers have been thinking and writing about for several years. For 2008, pain in women will be the focus of the International Association for the Study of Pain (IASP) and its global pain public awareness initiative. Every year IASP identifies an area of global emphasis in pain management to help improve worldwide public awareness of untreated and under-treated pain in various populations.

“Despite the extensive number of published studies exploring gender differences in pain mechanisms and responses, we still need better fundamental knowledge about pain mechanisms and how they might differ in men and women,” said Roger Fillingim, PhD, professor, University of Florida College of Dentistry. “If the biology of pain is different in men and women, then we might be able to develop gender-specific pain treatments.”

Fillingim and other researchers exploring gender differences in pain mechanisms and pain responses have reported through the years that women do report more pain and experience it in more locations in the body than men. Many studies have been conducted using heat, cold, pressure, and other painful stimuli to measure pain responses and duration in men and women.

For Fillingim, a key concern is learning why women seem to be more vulnerable to certain pain syndromes. “Conditions like fibromyalgia, irritable bowel syndrome, migraines and TMJ pain are far more prevalent in women than men, yet we have no evidence to connect these disorders biologically to women more extensively than in men,” Fillingim said. “For example, certain types of migraines have been linked to the onset of a menstrual cycle, but that is one of the few definitive sex-based links explaining higher pain prevalence in women.”

A study published in 2005 in The Journal of Pain showed that the relationship between heart rate and pain perception is gender-related. Heart rate increases are considered to be a good indicator of pain levels in men. This could be explained by the role sex hormones play in pain perception and by gender differences in the reactivity of the cardiovascular and central nervous systems. Other studies using a different class of opioids have shown that women experience more pain relief than men after oral surgery.

In another 2005 study in The Journal of Pain, Fillingim found that morphine provided adequate analgesia to all experimental pain stimuli given to the study group, without sex differences. Women, however, reported more side effects while men had greater increases in resting blood pressure in response to the medication.

Research, therefore, has shown that women experience and report more pain than men and have more side effects to opioids, while men show heart rate and blood pressure increases in response to pain stimuli and opioids. Still, there is much discussion in the pain-research community about why gender differences exist. Though considerable attention has been devoted to biological variables such as hormonal influences and genetics, more and more studies are focusing on the psychological and social factors that might account for gender differences in reporting pain.

“We do know women report pain more often than men but we don’t know why,” said Fillingim. “It is unlikely that women simply report more pain, rather we need to better understand the physiological, social and psychological forces that govern this phenomenon. Obviously we need more research to learn if there are fundamental, gender-specific differences in basic pain mechanisms.”

New Law Requires Tamper Proof RX Forms for Medicaid

As of October 1, 2007, a new federal law goes into effect requiring all prescriptions for Medicaid beneficiaries to be written on tamper proof prescription forms. Many clinicians, healthcare advocates, and patients are concerned that the new requirement may cause an interruption in care, especially if prescribers are unaware of the new mandate, or if there is difficulty obtaining the proper forms. The Centers for Medicare and Medicaid Services (CMS) recently sent a letter about the law to state Medicaid officials.

Get the word out about the new requirement so that pain care is not disrupted.

Highlights from the Clinical Journal of Pain

The following highlights summarize selected articles from the July/August 2007 issue (volume 23, number 6).

Changes in Pain Perception and Descending Inhibitory Controls Start at Middle Age in Healthy Adults
Marianne Larivière,* MSc, Philippe Goffaux, PhD,** Serge Marchand, PhD,* ** and Nancy Julien, MSc*
*Departément des Sciences de la Santé, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda
**Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada

Although previous studies have shown a reduction of diffuse noxious inhibitory controls (DNICs) in elderly adults compared to young adults, this study addresses whether middle-aged adults also show a DNIC deficit. Pain thresholds (PTs) of young, middle-aged, and elderly healthy volunteers were assessed before and during a cold-pressor task in 7°C water, and acute nociceptive stimuli were administered using a thermode with varying degrees of painless and painful heat pulses. Findings showed that thermal PTs increase by middle age; however, the DNIC-induced increase in PT dampens progressively with advancing age. “The findings tell us that changes in pain perception and endogenous pain modulation arrive earlier than previously suggested,” according to the authors, who suggest including a middle-aged group in studies that compare pain measures across the adult lifespan.

Validation and Reliability of the Neuropathic Pain Scale in Multiple Sclerosis
David J. Rog, BMBS, Walton Centre for Neurology and Neurosurgery, Liverpool, UK; Turo J. Nurmikko, PhD, Pain Research Institute, Liverpool, UK, Tim Friede, PhD, Warwick Medical School, University of Warwick, Coventry, UK; and Carolyn A. Young, MD, Walton Centre for Neurology and Neurosurgery, Liverpool, UK

Central neuropathic pain occurs in about 28% of patients with multiple sclerosis (MS). The Neuropathic Pain Scale (NPS) has received preliminary validation in peripheral neuropathic pain conditions, and this study aimed to validate its use in MS central pain syndromes. One hundred and forty-one patients with MS were administered the NPS, along with the Short Form McGill Pain Questionnaire, the Hospital Anxiety and Depression Scale, and Short Form 26 Health Survey. It was found that the NPS appears to be a useful tool in assessing pain in MS patients and possibly in measuring outcomes of therapeutic interventions. “It captures a large proportion of the patient’s own descriptors of their neuropathic pain, is largely free of floor and ceiling effects, can be administered both postally and in the hospital with little missing data, and shows both convergent and discriminant validity with other commonly used scales,” the authors said.

Research Grants from RSDSA

Since 1992, The Reflex Sympathetic Dystrophy Syndrome Association (RSDSA) has funded more than $1,161,050 in fellowships and research grants. This year’s grant application deadlines are approaching. To learn more, visit www.rsds.org/3/research/index.html.

APS Call for Paper and Poster Abstracts

The call for paper and poster abstracts for the 27th Annual Scientific Meeting, May 7–10, 2008, in Tampa, FL, is now available online. Abstracts can be submitted until 11:59 pm Pacific Time on Tuesday, October 30.

Members Respond to APS Letter to Washington AMDG

The last issue of APS E-News featured APS’s response to the Washington State Agency Medical Directors' Group (AMDG) opioid dosing guideline. That particular story received the highest readership of any APS E-News story. Several members felt so strongly about the issue that they took the time to share their views. Member responses on the issue varied. Some members expressed agreement with and appreciation for APS’s response. Others wrote to express concern in general about the undertreatment of pain and called on APS to make more statements about broader issues impacting pain prevention and treatment rather than prescription misuse.

If you have an opinion to share, write to APS at mrutkowski@connect2amc.com.

APS Hosts First Corporate Advisory Meeting

On August 28, more than 40 corporate members representing 15 different companies met with APS leaders in the Chicago area. APS hosted this event to provide a forum for idea exchange between corporate members and the society. Corporate members were briefed by President Judy Paice and executive committee members and asked to provide feedback on the society’s strategic plan and recent achievements. Outcomes from the meeting will be shared with the APS Board in October as a means to inform their strategic planning process. Results from recent surveys of all members will be used as well.

NIDA Mini Convention: Frontiers in Addiction

At the National Institute on Drug Abuse mini-convention, a satellite meeting of the Society for Neuroscience (SfN) Annual Meeting, outstanding scientists will present recent findings and discuss future directions in the neurobiology of drug abuse and addiction. The mini-convention includes four symposia, the SfN Jacob Waletzky Memorial Lecture, and a poster session for early career investigators. For more information, visit www.sei2003.com/nida/frontiers2007/welcome.htm.