Lower Serum Calcium Levels Associated with Disrupted Sleep and Rest–Activity Rhythm in Shift Workers

Abstract

Vitamin D deficiency is prevalent in many developed countries, and several studies suggest that vitamin D plays an essential role in brain function. A recent study showed that vitamin D deficiency was closely associated with daytime sleepiness and shorter sleep time. The relationshipbetween vitamin D levels and calcium levels is well established, and calcium level regulates slow-wave sleep generation. It is conceivable that the sleep disturbance in vitamin D deficiency may be due to an altered calcium level. Nonetheless, calcium levels, sleep disturbances, and activity rhythms have not been investigated directly. Therefore, we hypothesized that calcium and vitamin D levels might be important in regulating sleep and activity rhythm, and we analyzed the correlation with calcium levels by actigraphy analysis. Interestingly, a negative correlation was found between calcium level and sleep latency, total sleep time, use of sleep medicine, and daytime dysfunction among shift workers. In contrast, non-shift workers showed a negative correlation between the calcium level and the circadian phase. These findings suggest that low serum calcium levels may disrupt sleep–wake control and rest–activity rhythm, even if they are within the normal range.

Effect of circadian clock and claudin regulations on inulin-induced calcium absorption in the mouse intestinal tract

“…This indicates that Ca 2+ -dependent neural hyperpolarization pathways are very closely related to slow-wave sleep. In a recent human study, shift workers with higher serum calcium concentrations tended to fall asleep more easily and have shorter total sleep times, whereas no such significant correlation was found in non-shift workers, and a negative correlation was found between the calcium concentration and peak time of daily activity as measured by actigraphy [ 55 ]. Therefore, the fact that increased calcium absorption appears at the beginning of the resting period may be an important physiological effect for better quality sleep.…”

“…negative correlation was found between the calcium concentration and peak time of daily activity as measured by actigraphy [54]. Therefore, the fact that increased calcium absorption appears at the beginning of the resting period may be an important physiological effect for better quality sleep.…”

Effect of Circadian Rhythm Disturbance on the Human Musculoskeletal System and the Importance of Nutritional Strategies

“…The deficiencies are worldwide issues which are mainly associated with bone diseases [ 123 ]. Eventually, a recent study among shift workers showed that low serum calcium levels might be associated with circadian dysregulation as well as sleep disturbance [ 124 ]. Individuals with irregular sleep schedules may obtain less sun exposure, which contributes to vitamin D deficiency.…”

Effect of Food Intake on Sleep: Mechanisms and Recommendations

“…A study conducted on shift workers found a link between low calcium levels and daytime dysfunction, sleep latency, and total sleep time. [34] According to recent studies, calcium is essential for producing slow oscillations during NREM sleep. [35] Low calcium levels may make it difficult for slow wave activity to be produced, necessitating longer sleep cycles to relieve the pressure associated with them during the wake phase.…”

“…It is possible to assume that a low calcium level decreases slow-wave activity and lengthens total sleep time in order to preserve the homeostasis of slow-wave energy, which is the cumulative sum of slow-wave activity across total sleep duration. [34] The consumption of dairy products, which are high in tryptophan and calcium, has also been linked to reported improvements in sleep quality. Calcium facilitates the brain's use of tryptophan in the production of melatonin, enhancing sleep quality.…”