Acute effects of night work and meals on blood glucose levels.

Employees working at night are at increased risk of diabetes. A possible mechanism is related to differences in glucose regulation at night. Laboratory simulated night work studies show regulation of blood glucose is impaired at night. Regular exposure to high glucose levels at night may explain the observed relationship between night work and diabetes. We performed a field study of 19 nonsmoking women from the health-care sector to investigate how night work and the composition of meals affect post-prandial blood glucose levels. Blood glucose levels were self-assessed by finger-prick blood sampling using the Beurer blood glucose monitoring system. Measurements were done before and 15, 30, 60, and 120 min after different test meals: a nighttime high sugar meal during a night shift and during a day shift, and a reference (low sugar) meal under these same two conditions. There was a statistically significant difference in blood glucose concentration between the four test meal conditions (P = .0086). Post-meal blood glucose levels following the night-shift meals, compared to following daytime meals, rose faster and remained elevated for longer a duration of time. At the 15 min time point following the high sugar test meal, the blood glucose concentration was 8.3 mmol/L when consumed at night vs. 7.3 mmol/L when consumed during the day. We found no difference in area under the blood glucose concentration-time curve (AUC) after consumption of the high or low sugar test meals during the night shift compared with consumption of them during the day. Our findings indicate the glucose levels in response to food intake by female night working healthcare assistants are higher following the nighttime compared with daytime consumption of a high sugar content meal. However, we did not find a difference in total glucose exposure across time (assessed as AUC) after eating a high vs. low sugar meal during the night shift.

Development and validation of a vitamin D status prediction model in Danish pregnant women: a study of the Danish National Birth Cohort.

Vitamin D has been hypothesized to reduce risk of pregnancy complications such as preeclampsia, gestational diabetes mellitus, and preterm delivery. However, many of these outcomes are rare and require a large sample size to study, representing a challenge for cohorts with a limited number of preserved samples. The aims of this study were to (1) identify predictors of serum 25-hydroxy-vitamin D (25(OH)D) among pregnant women in a subsample (N = 1494) of the Danish National Birth Cohort (DNBC) and (2) develop and validate a score predicting 25(OH)D-status in order to explore associations between vitamin D and maternal and offspring health outcomes in the DNBC. In our study sample, 42.3% of the population had deficient levels of vitamin D (<50 nmol/L 25(OH)D) and average levels of 25(OH)D-status were 56.7(s.d. 24.6) nmol/L. A prediction model consisting of intake of vitamin D from diet and supplements, outdoor physical activity, tanning bed use, smoking, and month of blood draw explained 40.1% of the variance in 25(OH)D and mean measured 25(OH)D-level increased linearly by decile of predicted 25(OH)D-score. In total 32.2% of the women were placed in the same quintile by both measured and predicted 25(OH)D-values and 69.9% were placed in the same or adjacent quintile by both methods. Cohen's weighted kappa coefficient (Κ = 0.3) reflected fair agreement between measured 25(OH)D-levels and predicted 25(OH)D-score. These results are comparable to other settings in which vitamin D scores have shown similar associations with disease outcomes as measured 25(OH)D-levels. Our findings suggest that predicted 25(OH)D-scores may be a useful alternative to measured 25(OH)D for examining associations between vitamin D and disease outcomes in the DNBC cohort, but cannot substitute for measured 25(OH)D-levels for estimates of prevalence.