Secondary causes of restless legs syndrome in older people

Secondary causes of restless legs syndrome (RLS) have been reported to be more common in those with late-onset RLS. However, 'late-onset' in previous studies was defined as onset after 45 years.

To determine the prevalence of secondary causes of RLS and the relationship between aetiological factors and age of symptom onset in an older population.

Prospective study conducted over a 5-year period.

80 consecutive non-related patients diagnosed with RLS.

Patients were assessed according to a standard protocol. Age at symptom onset, severity of symptoms, neurological findings and laboratory tests were examined.

Iron deficiency (serum ferritin <50 ng/ml) was present in 22% of patients with onset before 50 years, 39% of those with onset at 50 to 64 years and 58% in those with onset after 64 years (P = 0.009). Clinical neuropathy was also more common in older-onset patients (P = 0.08). Family history was positive in 39%, 23% and 8% of these groups, respectively (P = 0.008).

Secondary causes of RLS become more common and a positive family history less common with increased age of symptom onset.