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Objective Low circulating serum levels of 25-hydroxyvitamin D (referred to hereafter as vitamin D) have been correlated with many health conditions, including chronic pain. Recent clinical practice guidelines define vitamin D levels <20 ng/ml as deficient and levels of 21-29 ng/ml as insufficient. Vitamin D insufficiency, including the most severe levels of deficiency, is more prevalent in black Americans. Ethnic and race group differences have been reported in both clinical and experimental pain, with black Americans reporting increased pain. The purpose of this study was to examine whether variations in vitamin D levels contribute to race differences in knee osteoarthritis pain. Methods The sample consisted of 94 participants (74% women), including 45 blacks and 49 whites with symptomatic knee osteoarthritis. Their average age was 55.8 years (range 45-71 years). Participants completed a questionnaire on knee osteoarthritis symptoms and underwent quantitative sensory testing, including measures of sensitivity to heat-induced and mechanically induced pain. Results Blacks had significantly lower levels of vitamin D compared to whites, demonstrated greater clinical pain, and showed greater sensitivity to heat-induced and mechanically induced pain. Low levels of vitamin D predicted increased experimental pain sensitivity, but did not predict self-reported clinical pain. Group differences in vitamin D levels significantly predicted group differences in heat pain and pressure pain thresholds at the index knee and ipsilateral forearm. Conclusion These data demonstrate that race differences in experimental pain are mediated by differences in the vitamin D level. Vitamin D deficiency may be a risk factor for increased knee osteoarthritis pain in black Americans. [ABSTRACT FROM AUTHOR]

Sleep disorders are prevalent among college students and are associated with poor academic performance. Few studies have included a clinical interview to comprehensively assess sleep disorder diagnostic criteria or assessed academic functioning (e.g., class attendance). College students (n = 277) were recruited to complete sleep questionnaires, a sleep diary for two weeks and, if indicated, a semi-structured clinical interview. Based on questionnaire data, students were categorized as being at risk versus not at risk for a sleep disorder. Based on the semi-structured clinical interview, students were categorized as meeting versus not meeting diagnostic criteria for a sleep disorder. Academic performance and functioning were assessed in all students to determine the association between the presence of sleep disorders and academic performance and functioning. In models adjusted for age, sex, race, and credit hours completed, students at risk for a sleep disorder (38.6% of the sample) reported missing more classes due to oversleeping (p = 0.001) and illness (p = 0.014), and fell asleep in class more often (p = 0.030) than their peers not at risk. Students with a sleep disorder (24.8% of the sample) reported missing more classes due to illness (p = 0.024) than those without a sleep disorder. There were no differences in grade point average between students at risk versus not at risk or with versus without a sleep disorder. Sleep disorder symptoms and diagnoses were significantly associated with worse academic functioning but not performance. Assessment and treatment of sleep disorders early in college students' career may be important for optimal academic functioning. [ABSTRACT FROM AUTHOR]

Aims To assess the relationship between pain and HbA1c levels in a predominantly black population with diabetes, and to determine whether self-management behaviours (exercise and diet) and symptoms of depression mediate this relationship. Methods We analysed cross-sectional data from 417 community-dwelling individuals with diabetes in rural Alabama, USA. Binary logistic regression was used to analyse the relationship between pain and HbA1c levels, defined as relatively good [≤ 64 mmol/mol (≤ 8.0%)] and relatively poor [> 64 mmol/mol (> 8.0%)], after adjusting for sociodemographics, insulin use, medication count, cigarette smoking history and body mass index ( BMI). We examined the mediating roles of exercise, diet, and symptoms of depression using bootstrapping. Results Participants were primarily black (86.6%), female (76.1%) and reported an annual income of ≤$20,000 (52.7%). Their mean ( sd) age was 59.6 (12.8) years. The majority of the participants reported moderate to extreme pain (71.5%). Participants reporting pain were more than twice as likely to have HbA1c levels > 64 mmol/mol (8.0%) in the fully adjusted model (odds ratio 2.33 [95% CI 1.28-4.24]; P < 0.05). Diet significantly mediated the relationship between pain and HbA1c control (β = 0.06; 95% CI: 0.01-0.17), but only in the unadjusted model. Exercise and symptoms of depression were not significant mediators. Conclusions A significant independent relationship between pain and HbA1c control was found in this mainly black population, which was not explained by self-management behaviours or symptoms of depression. Future research is needed to delineate the mechanism by which pain influences HbA1c control, especially among black people with diabetes on low incomes. [ABSTRACT FROM AUTHOR]