Prospective study of Restless Legs Syndrome in a blood donors’ sample

Restless Legs Syndrome (RLS) is characterised by the presence of legs discomfort and restlessness, that appears at rest with worsening during evening and night, and can be relieved with movement. The prevalence of RLS in the general population is 7,2 -11,5%, with a female predominance, and a trend to increase with age.

The causes of RLS are complex, involving genetic factors and a disorder of iron metabolism. Iron deficiency anaemia increases the risk of RLS by a factor of six, although most RLS patients show iron deficiency without anaemia. Each donation causes an estimated iron loss of 200-250 mg, therefore, repeat blood donation may increase the risk of iron deficiency and, therefore the risk of RLS. Previous studies regarding RLS prevalence in blood donors have shown controversial results.

Our study aimed to assess the prevalence of RLS in a sample of Spanish blood donors and determined its potential correlation with iron metabolism parameters.

We included 129 blood donors, 54.3% of whom were men, having a mean age of 39.44 years. We stratified donors into two groups: sporadic donors who made less than one donation/year and repeat donors who made more than one donation/year. They underwent a physical examination and blood test, including iron metabolism parameters (haemoglobin, ferritin, transferrin saturation index and soluble transferrin receptor). To asses the presence of RLS we used a screening questionnaire followed by a prospective follow-up including a clinical phone interview.

We found that the 44,2% of our sample showed non-anaemic iron deficiency, defined as a ferritin value below 50 µg/l, and it was statistically higher in women and repeat donors. The prevalence of RLS was 14.1% at inclusion, and increased prospectively to 19.5%. Despite the high prevalence of non-anaemic iron deficiency among blood donor,s there was no association between ferritin, transferrin saturation index, soluble transferrin receptor concentration values and RLS diagnosis. RLS was much more frequent in women, with a 2-3:1 ratio. After a multivariate analysis, gender was the only variable significantly associated with a RLS diagnosis, even after adjusting for age, ferritin and frequency of donation.

These results have shown that RLS prevalence in a sample of Spanish blood donors is similar to the general population. Blood donation can promote non-anaemic iron deficiency, although this iron deficiency was not associated with an increase in RLS prevalence in blood donors. Female gender was the stronger factor associated with RLS diagnosis, regardless of other variables.