The effect of caffeine supplementation on exercise performance evaluated by a novel animal model

Introduction: Caffeinated drinks are used for improve performance. Animal models represent investigational strategy that circumvents most of the drawbacks of research in humans, including motivational factors and the placebo effect. No animal model that could test whether different forms of administering caffeine affect exercise propensity was found in the literature. Methods: An animal model of grouped voluntary exercise was tested. Two-month-old male C57/bl mice were housed in a cage fitted with one running wheel and a monitoring system. Six animals per cage were introduced individually. To assess the sensitivity of the model, the effect of different caffeinated drinks was observed in mice exercising ad libitum. During 2 days, the mice received: 1) pure anhydrous caffeine 0.125 mg/mL (PC), 2) cola drink (CC), and 3) caffeine-taurine-glucuronolactone drink (CTG), intercalating wash-out periods of 2 days, receiving pure water. Results: The distance run during the periods of water ingestion was significantly lower than during the periods of stimulant drinks ingestion: PC (5.6 ± 1.3 km; p = 0.02), of CC ingestion (7.6 ± 0.6 km; p = 0.001), and of CTG ingestion (8.3 ± 1.6 km; p = 0.009). The performances when ingesting the three caffeinated drinks do not follow a dose-response curve. Conclusions: The model described here was able to measure the effect of caffeine intake on voluntary exercise of mice. The sensitivity of the model to the effect of caffeine needs to be further validated. The action of each component of the drinks on exercise performance needs to be clarified in future research. The present model is adequate for such investigation (AU)

Is sleep apnea a winter disease?: meteorologic and sleep laboratory evidence collected over 1 decade.

BACKGROUND: The severity of obstructive sleep apnea increases by influence of conditions that are more frequent in winter. The hypothesis that the apnea-hypopnea index (AHI) of different patients undergoing polysomnography may be seasonally affected was tested. METHODS: The retrospectively analyzed database included 7,523 patients of both sexes who underwent in-laboratory baseline polysomnography to investigate any complaint of disordered sleep, during 1 decade, between January 2000 and December 2009. Data on climate and air pollution were obtained from official organizations. AHI was the main outcome variable. Cosinor analysis, a statistical method for the investigation of time series, was used to detect seasonality. RESULTS: The cosinor analysis confirmed the existence of a circannual pattern of AHI, with acrophase in winter and nadir during the summer. The seasonality is significant even after adjusting for sex, age, BMI, neck circumference, and relative air humidity. Median (25-75 interquartile range) AHI in the 6 months with colder weather was 17.8 (6.5-40.6/h), and in the warmer weather was 15.0 (5.7-33.2/h). The AHI correlated inversely with ambient temperature and directly with atmospheric pressure, relative air humidity, and carbon monoxide levels. Correlations with precipitation, particulate air matter < 10 µm, sulfur dioxide, and ozone were nonsignificant. CONCLUSIONS: More sleep-disordered breathing events were recorded in winter than in other seasons. Cosinor analysis uncovered a significant seasonal pattern in the AHI of different patients undergoing polysomnography, independent of sex, age, BMI, neck circumference, and relative air humidity. This finding suggests that obstructive sleep apnea severity may be associated with other seasonal epidemiologic phenomena.

Immediate and overnight recumbence-dependent changes of neck circumference: relationship with OSA severity in obese and nonobese subjects.

BACKGROUND: Overnight increases in neck circumference - attributed to rostral fluid displacement - correlate with the severity of obstructive sleep apnea (OSA). No studies were found investigating the relationship between OSA severity and recumbence-related immediate changes in neck circumference. We evaluated the relationship of OSA severity with immediate recumbence-related and overnight changes in neck circumference in obese and nonobese subjects. METHODS: Male patients undergoing full-night in-laboratory polysomnography had their neck and ankle circumferences determined before and after sleep, both while standing and supine. Circumference changes were calculated by the difference between standing and recumbent positions (Immediate Change) and between before and after sleep (Overnight Change). RESULTS: Immediate Change in neck circumference showed a linear significant correlation with apnea-hypopnea index (AHI; r=0.37373; p=0.012) and with lowest O2 saturation (r=-0.35355; p=0.017). In a multivariate model to predict AHI, adjusting for age and obesity, Immediate Change in neck circumference is the only significant regressor (beta=0.34; p=0.03). The Overnight Change in neck circumference correlated neither with the AHI nor with the lowest SaO2. CONCLUSION: Correlation of AHI with the immediate increase in neck circumference on assuming recumbence indicates that fast components of tissue displacement, besides overnight fluid displacement, may have implications in the pathogenesis of OSA.