Augmented depression and reduced excitability of the central nervous system (CNS) by cadmium in the rat

The Effect of Cadmium on Sleep Parameters Assessed in Polysomnographic Studies: A Case-Control Study

Cadmium is a heavy metal that accumulates in the body due to environmental and occupational exposure. The main form of environmental exposure to cadmium is related to cigarette smoking. The primary aim of this study was to evaluate the effect of cadmium on numerous sleep parameters with the use of polysomnography. The secondary aim of this study was to investigate if environmental exposure to cadmium is a risk factor for the intensity of sleep bruxism (SB).

METHODS

A total of 44 adults underwent a full night of polysomnographic examination. The polysomnograms were assessed according to guidelines set out by the American Academy of Sleep Medicine (AASM). The concentration of cadmium in the blood and urine was determined spectrophotometrically.

RESULTS

The polysomnographic examination confirmed that cadmium, age, male gender and smoking status are independent risk factors for an increase in the apnea-hypopnea index (AHI). Cadmium alters sleep architecture by favoring sleep fragmentation and decreasing the duration of the rapid eye movement (REM) phase of sleep. However, cadmium exposure is not a risk factor for the development of sleep bruxism.

CONCLUSIONS

In summary, this study demonstrates that cadmium affects sleep architecture and is a risk factor for the development of obstructive sleep apnea; however, it does not affect sleep bruxism.

Low-level cadmium exposure increases one-way avoidance in juvenile rats

Twenty-seven pregnant rats from three genetic lines, Roman High Avoidance (RHA), Roman Low Avoidance (RLA), and Satinder's Heterogeneous Stock (SHS), received daily SC injections of either 0.075 mg/kg CdCl2 (low dose), 0.225 mg/kg CdCl2 (high dose), or an equivalent volume of saline vehicle (control) throughout gestation. Cd-exposed progeny from the RHA genetic line weighed significantly less than RHA control progeny (pd 35-44); however, SHS progeny from the low-dose group weighed significantly more than progeny from any other group (pd 14-44). Unconditioned escape response (UER) level was determined on pd 39. Progeny from the high-dose group required a significantly lower UER level as compared to the low-dose group. Acquisition of conditioned avoidance responses was tested from pd 41 to 44. There were significant differences due to dose for one-way avoidance responses. Cd-related differences in one-way avoidance were restricted to progeny from the SHS genetic line. SHS progeny from the high-dose group demonstrated significantly more one-way responses when compared to the control group. Differences in avoidance responses are discussed in relation to Cd-induced hypernociception. The concentration of Cd in the liver and kidney of dams and progeny was determined by Inductively Coupled Plasma spectroscopy (ICP). There were significant dose-related differences in Cd concentration in maternal tissues.

Neuropsychological effects of occupational exposure to cadmium

Neuropsychological functioning was measured in 31 male workers exposed to cadmium in a refrigerator coil manufacturing plant. Workers with high urinary cadmium levels performed less well than did those with low urinary cadmium levels on measures of attention, psychomotor speed, and memory. There were modest correlations between one of two biologic measures of cadmium exposure and neuropsychological performance. The neuropsychological impairments cannot readily be attributed to exposure to other neurotoxins, alcohol intake, CNS effects of renal dysfunction, or psychological distress. Cadmium body burden has previously been related to intelligence and school achievement of children; this study would appear to be the first to suggest that occupational exposure to cadmium is associated with cognitive impairment in adults. Cadmium interferes with several important nervous system functions, but the mechanisms of neurotoxicity remain uncertain.