The Role of Periodic Limb Movement in Sleep of Patients with Sickle Cell Disease.

In last decade, there has been growing research in sleep disorders associated with sickle cell disease (SCD), particularly focusing on oxyhemoglobin desaturation. The coexistence of periodic limb movement (PLM) and anemia is well known, however it remains controversial to which extent dopamine deficiency, lower serum ferritin levels or iron deficiency contribute to the pathophysiology of PLM in anemia.

The aim of this study is to evaluate the relationship between PLM and other manifestations of SCD

Eight male patients with SCD were age and BMI-matched to 16 healthy controls (1:2) for sleep evaluation by clinical inventory and polysomnography (PSG). PLMS were defined as limbs movements lasting 0.5–5 seconds that recur every 5 to 90 seconds in a series of ≥ 4. Serum levels of ferritin and hemoglobin were assessed.

Comparing to controls (aged 28.6 ±5.9 yrs, BMI of 22.1 ±3.8 kg/m²), SCD patients (aged 28.0 ±7.3 yrs, BMI of 21.4 ±4.6 kg/m² p>0.05, both) scored their sleep satisfaction as moderate (75% vs. 12.5%, p=0.005), whereas 50% of controls scored it as very satisfactory (vs. none of the SCD patients, p=0.02). Awakenings in the middle of the night were frequently reported by SCD patients (87.5% vs. 43.7%, p= 0.05) as well as pain complaints (87.5% vs. 37.5%, p=0.03). PSG data revealed that, compared to controls, SCD patients exhibited decrease in sleep efficiency (76.7% ±12.6 vs. 87.9% ±4.8, p=0.004), in REM sleep percentage (10.6 % ±6.0 vs. 20.3% ±5.8, p=0.001), and increase in wake after sleep onset (65.3%±38.9 vs. 32.4% ±20.2, p=0.012), arousal index (16.3/hour ±8.5 vs. 9.5/hour ±4.9, p=0.021), PLM index (13.1 ±10.1 vs. 2.8 ±3.3, p= 0.001), apnea hypopnea index (8.8/hour ±5.6 vs. 3.4/hour ±5.0, p=0.025). Lower mean oxyhemoglobin saturation (88.0 mmHg ±3.4 vs. 92.4 mmHg ±5.4, p=0.049), and hemoglobin levels (8.7g/dl ±1.1 vs. 15.8g/dl ±0.7, p<0.001) were also verified in SCD patients. Interestingly, ferritin levels did not differ between groups (209.6±132.8 in SCD patients vs. 214.8 ±142.2, p=0.949). Linear regression showed that SCD condition represented an independent risk feature for PLM (R² = 0.51, p<0.001). Correlation between PLM and the number of comorbities related to SCD was substantial (r=0.79, p=0.02)

Subjective sleep complaints reported by patiens with SCD were supported by PSG findings of sleep disruption and lower mean oxyhemoglobin saturation. Increase in PLM in SCD patients correlated the number of comorbities of the disease. In contrast with the literature, ferritin did not play a role in the pathophysiology of PLM in these patients.

This study was supported by FAPESP CEPID 98/14303-3 and AFIP

No relevant conflicts of interest to declare.