Thymus Activity, Vitamin D, and Respiratory Infections in Adolescent Swimmers.

BACKGROUND: Several studies have identified associations between low vitamin D concentrations and risk of upper respiratory infections (URI). T lymphocytes have a major anti-viral role, are affected by vitamin D metabolism, and may mediate the link between vitamin D and URIs. Competitive swimmers have a relatively high rate of URIs, alongside a high prevalence of low vitamin D concentration. OBJECTIVES: To examine the associations linking T cell receptor excision circles (TREC, markers of thymus activity), circulating 25(OH)D concentrations and the effect of vitamin D supplementation, and URI symptoms in young competitive swimmers. METHODS: We tested 82 adolescent swimmers for serum 25(OH)D and TREC concentrations and found that 55 had vitamin D insufficiency. Randomized supplementation of either vitamin D3 or placebo was given for 12 winter weeks. URI symptoms were recorded weekly. The associations between TREC copy numbers, vitamin D and URI burden were examined. RESULTS: TREC concentrations decreased with the participants' age (r = -0.346, P = 0.003), with no significant between-gender difference. TREC concentrations did not materially differ among subjects with normal, insufficient or deficient vitamin D status, and were not affected by vitamin D supplementation. No significant correlations were found between TREC levels or their changes during the study period, and mean URI severity or duration. CONCLUSIONS: Thymus activity, represented by higher TREC levels, was not related to vitamin D concentrations or status, and was not affected by vitamin D supplementation in adolescent swimmers. TREC concentrations were not associated with URI severity or duration in this population.

Vitamin D Supplementation and Physical Performance in Adolescent Swimmers.

It is hypothesized that vitamin D insufficiency in athletes might negatively affect sport performance. The objective of this study was to examine the effect of vitamin D3 supplementation on physical performance of adolescent swimmers with vitamin D insufficiency. Fifty-three adolescent competitive swimmers with vitamin D insufficiency (serum 25-hydroxyvitamin-D concentrations (25(OH)D) < 30 ng/ml, mean 24.2 ± 4.8 ng/ml) were randomized to receive 2,000 IU/day of vitamin D3 or placebo for 12 weeks. Swimming performance at several speeds, arm-grip strength, and one-legged balance, were measured before and after supplementation. The age-adjusted changes in performance variables during the study were compared between groups. 25(OH) D concentrations at study end were significantly higher in the vitamin group compared with the placebo group (29.6 ± 6.5 ng/ml vs. 20.3 ± 4.2 ng/ml, p < .001), yet only 48% of the vitamin group became vitamin D sufficient with this dosing. No between-group differences were found in the changes of the performance variables tested. No significant differences in performance were found between participants that became vitamin D sufficient, and those who did not. No significant correlation was found between the change in serum 25(OH)D and age-adjusted balance, strength or swimming performance at study end. Vitamin D3 supplementation that raised serum 25(OH)D concentrations by a mean of 9.3 ng/ml above placebo in adolescent swimmers with vitamin D insufficiency, did not improve physical performance more than placebo.

Vitamin D supplementation and upper respiratory tract infections in adolescent swimmers: a randomized controlled trial.

Observational studies identified associations between vitamin D insufficiency (serum 25(OH)D < 30ng·ml-1) and risk of upper respiratory infection (URI). Swimmers are highly prone to URIs, which might hinder their performance. The aim of this study was to examine if vitamin D3 supplementation reduces URI burden in vitamin D-insufficient swimmers. Fifty-five competitive adolescent swimmers with vitamin D insufficiency were randomized to receive vitamin D3 (2,000IU·d-1) or placebo for 12 winter weeks. A URI symptom questionnaire was completed weekly. Serum 25(OH)D concentrations were measured by radio-immunoassay before and after supplementation. We used linear regression to examine the relation between the change in 25(OH)D concentrations during the trial, and the duration and severity of URIs. There were no between-group differences in the frequency, severity, or duration of URIs. Exploratory analyses revealed that in the placebo group only, the change in 25(OH)D concentrations during the trial was highly associated with the duration of URIs (r = -0.90,p < .001), and moderately associated with the severity of URIs (r = -0.65,p = .043). The between-group differences for duration were highly significant. Vitamin D3 supplementation in adolescent swimmers with vitamin D insufficiency did not reduce URI burden. However, larger decreases in serum 25(OH)D concentrations were associated with significantly longer and more severe URI episodes.

Vitamin D concentrations and physical performance in competitive adolescent swimmers.

Serum vitamin D concentrations (25[OH]D) are associated with physical performance in the general population, but few studies have been published in athletes. 80 competitive adolescent swimmers from both sexes were tested for serum 25(OH)D concentrations, grip strength, balance and swimming performance at several speeds. Spearman's correlations were used to examine the associations between 25(OH)D concentrations and age-adjusted measures of performance. Performance parameters were also compared between vitamin D sufficient (n = 27), insufficient (25[OH]D ranging 20-29.9 ng/ml, n = 42), and deficient (25[OH]D < 20 ng/ ml, n = 11) participants. No significant associations were found between serum 25(OH)D concentrations and any of the performance measures, with no significant differences found between vitamin D sufficient, insufficient and deficient participants. In competitive adolescent swimmers, serum vitamin D concentrations were not associated with strength, balance or swimming performance. Vitamin D insufficient/deficient swimmers did not have reduced performance.

Exploring physician perceptions of the impact of emotions on behaviour during interactions with patients.

BACKGROUND: There is relatively little research on affective influences on physician behaviour, especially on prescribing and referrals. Affects include transitory moods and lasting emotions. OBJECTIVES: We explored physician perceptions of the impact of four mood states on perceived rates of five behaviours: talking with patients, prescribing medications and referrals for laboratory tests, diagnostic tests and specialists. We also examined whether burnout modified the impact of moods on behaviour. METHODS: A total of 188 family physicians responded anonymously to a self-reporting questionnaire that assessed the perceived rate of behaviours when in a positive, negative, tired and nervous mood and burnout level. RESULTS: Five analyses of variance with repeated measures on mood states and contrast analyses computed the effects of mood and burnout on the behaviours. The mood factor was found significant for each of the behaviours, in all P < 0.001. The respondents reported that on good mood compared with negative mood days, they talked more, prescribed less and referred less. The burnout factor was also significant: high compared with low burnout physicians had higher perceived rates of all referral behaviours. Significant mood × burnout interactions indicated that the effects of mood were stronger among high compared with low burnout physicians. CONCLUSIONS: The physicians perceived that their moods had different effects on different behaviours: the negative mood decreased talking and increased prescribing and referral behaviours and vice versa for the positive mood. Burnout intensified the effects of moods. The incremental effects of negative moods and burnout may impair quality of health care and may be costly to health services.

The effect of vitamin C on upper respiratory infections in adolescent swimmers: a randomized trial.

The risk of upper respiratory infections (URIs) is increased in people who are under heavy physical stress, including recreational and competitive swimmers. Additional treatment options are needed, especially in the younger age group. The aim of this study was to determine whether 1 g/day vitamin C supplementation affects the rate, length, or severity of URIs in adolescent swimmers. We carried out a randomized, double-blind, placebo-controlled trial during three winter months, among 39 competitive young swimmers (mean age 13.8 ± 1.6 years) in Jerusalem, Israel. Vitamin C had no effect on the incidence of URIs (rate ratio = 1.01; 95% confidence interval (CI) = 0.70-1.46). The duration of respiratory infections was 22% shorter in vitamin C group, but the difference was not statistically significant. However, we found a significant interaction between vitamin C effect and sex, so that vitamin C shortened the duration of infections in male swimmers by 47% (95% CI: -80% to -14%), but had no effect on female swimmers (difference in duration: +17%; 95% CI: -38% to +71%). The effect of vitamin C on the severity of URIs was also different between male and female swimmers, so that vitamin C was beneficial for males, but not for females. Our study indicates that vitamin C does not affect the rate of respiratory infections in competitive swimmers. Nevertheless, we found that vitamin C decreased the duration and severity of respiratory infections in male swimmers, but not in females. This finding warrants further research.

Positive and negative work characteristics associated with burnout among primary care pediatricians.

BACKGROUND: There is little research regarding specific work features that might cause chronic stress and burnout among primary care pediatricians. The aim of the present study was first, to assess specific negative and positive characteristics of the job that might be related to burnout; and second, to compare burnout levels and work characteristics among board-certified versus general pediatricians; and clinic directors versus non-directors. METHODS: Questionnaires were sent to 200 pediatricians employed full-time in pediatric primary care community centers in the largest Israeli Health Maintenance Organization (HMO). Respondents replied anonymously. The questionnaires assessed sociodemographic details, burnout levels, and negative and positive job characteristics. RESULTS: There were no differences in burnout levels between board-certified and general pediatricians. Positive job features had stronger associations with burnout than negative features. Compared with general pediatricians, board-certified pediatricians reported significantly higher levels of negative features (e.g. conflicts between the medical and administrative system in the HMO; parents disregarding instructions); but higher levels of autonomy and appreciation from patients. Compared with regular pediatricians, clinic directors had significantly higher levels of negative job features (e.g. less access to resources); and higher levels of positive work features. CONCLUSIONS: The absence of positive job features (e.g. autonomy, recognition for one's work and utilization of skills) may be more important in causing burnout than the presence of negative characteristics (e.g. overload, demanding and noisy parents). It is consistent with recent suggestions that in the presence of positive features, employees can better tolerate stressful aspects of the job and still feel motivated and engaged.