Vitamin D, race, and experimental pain sensitivity in older adults with knee osteoarthritis

Psychological profiles and pain characteristics of older adults with knee osteoarthritis

OBJECTIVE

To identify psychological profiles in persons with knee osteoarthritis (OA) and to determine the relationship between these profiles and specific pain and sensory characteristics, including temporal summation and conditioned pain modulation.

METHODS

Individuals with knee OA (n = 194) completed psychological, health, and sensory assessments. Hierarchical cluster analysis was used to derive psychological profiles that were compared across several clinical pain/disability and experimental pain responses.

RESULTS

Cluster 1 had high optimism with low negative affect, pain vigilance, anger, and depression, along with the lowest self-reported pain/disability and the lowest sensitivity to mechanical, pressure, and thermal pain (P < 0.01 for all). Cluster 2 had low positive affect with high somatic reactivity, while cluster 3 showed high pain vigilance with low optimism. Clusters 2 and 3 had intermediate levels of self-reported pain/disability and cluster 3 experienced central sensitization to mechanical stimuli. Participants in cluster 3 also displayed significant pain facilitation (P < 0.05). Cluster 4 exhibited the highest pain vigilance, reactivity, negative affect, anger, and depression. These individuals experienced the highest self-reported pain/disability, including widespread pain (P < 0.001 for all). Cluster 4 was most sensitive to mechanical, pressure, and thermal stimuli, and showed significant central sensitization to mechanical and thermal stimuli (P < 0.001 for all).

CONCLUSION

Our findings demonstrate the existence of homogeneous psychological profiles displaying unique sets of clinical and somatosensory characteristics. Multidisciplinary treatment approaches consistent with the biopsychosocial model of pain should provide significant advantages if targeted to profiles such as those in our OA sample.

Temporal summation of pain as a prospective predictor of clinical pain severity in adults aged 45 years and older with knee osteoarthritis: ethnic differences

OBJECTIVE

Enhanced pain facilitation is reportedly an important contributor to the clinical pain experiences of individuals with knee osteoarthritis (OA). Ethnic differences in the prevalence and severity of knee OA in addition to associated pain are also well documented. Temporal summation (TS) of pain is a widely applicable quantitative sensory testing method that invokes neural mechanisms related to pain facilitatory processes. This study tested whether TS of pain, an index of pain facilitation, differentially predicts the clinical pain experiences of African Americans and non-Hispanic whites with symptomatic knee OA.

METHODS

A total of 225 study participants underwent assessment of TS of mechanical and heat pain stimuli applied to their most symptomatic knee and their ipsilateral hand (mechanical) or forearm (heat). Using telephone-based surveys, participants subsequently reported their average and worst clinical pain severity across four consecutive weeks after the assessment of TS.

RESULTS

In predicting future clinical pain, ethnicity interacted with TS of mechanical pain (but not heat pain), such that TS of mechanical pain at the knee significantly predicted greater clinical ratings of average (b = 0.02, p = .016) and worst (b = 0.02, p = .044) clinical pain for non-Hispanic whites but not African Americans (p values > .30).

CONCLUSIONS

These results reveal the importance of considering ethnicity when examining pain facilitation and the clinical pain of individuals with symptomatic knee OA. The results of this study are discussed in terms of ethnic differences in the predictors of clinical pain experiences among African Americans and non-Hispanic whites with knee OA.

Vitamin D and central hypersensitivity in patients with chronic pain

BACKGROUND

Low vitamin D is implicated in various chronic pain conditions with, however, inconclusive findings. Vitamin D might play an important role in mechanisms being involved in central processing of evoked pain stimuli but less so for spontaneous clinical pain.

OBJECTIVE

This study aims to examine the relation between low serum levels of 25-hydroxyvitamin D3 (25-OH D) and mechanical pain sensitivity.

DESIGN

We studied 174 patients (mean age 48 years, 53% women) with chronic pain. A standardized pain provocation test was applied, and pain intensity was rated on a numerical analogue scale (0-10). The widespread pain index and symptom severity score (including fatigue, waking unrefreshed, and cognitive symptoms) following the 2010 American College of Rheumatology preliminary diagnostic criteria for fibromyalgia were also assessed. Serum 25-OH D levels were measured with a chemiluminescent immunoassay.

RESULTS

Vitamin deficiency (25-OH D < 50 nmol/L) was present in 71% of chronic pain patients; another 21% had insufficient vitamin D (25-OH D < 75 nmol/L). After adjustment for demographic and clinical variables, there was a mean ± standard error of the mean increase in pain intensity of 0.61 ± 0.25 for each 25 nmol/L decrease in 25-OH D (P = 0.011). Lower 25-OH D levels were also related to greater symptom severity (r = -0.21, P = 0.008) but not to the widespread pain index (P = 0.83) and fibromyalgia (P = 0.51).

CONCLUSIONS

The findings suggest a role of low vitamin D levels for heightened central sensitivity, particularly augmented pain processing upon mechanical stimulation in chronic pain patients. Vitamin D seems comparably less important for self-reports of spontaneous chronic pain.

Does vitamin D improve osteoarthritis of the knee: a randomized controlled pilot trial

BACKGROUND

Animal, epidemiologic, and human clinical studies suggest a putative role for vitamin D in osteoarthritis (OA). Inadequate sunlight exposure and lower serum levels of 25(OH)D appear in some reports to be associated with an increased risk for progression of knee OA.

QUESTIONS/PURPOSES

We asked whether treatment with vitamin D would (1) reduce knee pain (WOMAC and VAS), (2) improve function (WOMAC), and (3) change levels of relevant biochemical markers in patients with knee OA with vitamin D insufficiency.

METHODS

This randomized controlled pilot trial prospectively enrolled 107 patients with knee OA with vitamin D insufficiency (25(OH)D ≤ 50 nmol/L) to receive oral vitamin D or placebo. The primary outcome measures were pain and function, and the secondary were biochemical markers. At baseline, the two groups were comparable. The patients were followed for 1 year.

RESULTS

At 12 months, knee pain had decreased in the vitamin D group by mean -0.26 (95% CI, -2.82 to -1.43) on VAS and -0.55 (95% CI, -0.07 to 1.02) on the WOMAC, whereas in the placebo group, it increased by mean 0.13 (95% CI, -0.03 to 0.29) on the VAS and 1.16 (95% CI, 0.82 to 1.49) on the WOMAC (effect size = 0.37 and 0.78). Likewise knee function improved in the vitamin D group by mean -1.36 (95% CI, -1.87 to -0.85) over the placebo group which had a mean 0.69 (95% CI, -0.03 to 1.41; effect size = 0.06). There were significant biochemical changes in serum total calcium, 25(OH)D and alkaline phosphatase.

CONCLUSIONS

The results above suggest there is a small but statistically significant clinical benefit to vitamin D treatment in patients with knee OA, although we recommend a long-term study to determine whether these changes are clinically important and whether they will be sustained with time. Further studies with long-term radiologic evaluations are needed.