Sleep In Patients with Sickle Cell Anemia and Priapism. A Case-Control Study

Priapism has been described as a sickle cell anemia (SCA) manifestation that occurs frequently during sleep. Given that hypoxemia has been implicated in the pathogenesis of SCA complications, we conducted this case control study of overnight polysomnography and penile tumescence recording in SCA adults with and without priapism, with the hypothesis that SCA patients with priapism might exhibit apnea and oxyhemoglobin desaturation during sleep.

The primary endpoint was to determine the relation between increase in penile tumescence (of 20%) and respiratory sleep events (apnea, hypopnea and desaturation >3%). Further sleep event associations with penile tumescence variation and other differences between groups regarding sleep pattern were assessed as secondary endpoints.

Seventeen SCA adults with priapism and 14 without history during the previous 12 month period were submitted to clinical interview and overnight polysomnography (Somnologica, Embla™), concomitantly performed with penile tumescence recording (Rigiscan Plus, Timm Medical™).

There was no statistical difference between groups (t test, Chi² or Fisher) in terms of age (mean ± s.d., 31.2 ± 14.0 vs. 27.8 ± 7.0 yrs, p=0.39), body mass index (20.9 ± 3.7 vs. 21.4 ± 2.3 kg/m², p=0.66), use of hydroxyurea (41 vs. 43%, p=1.00), levels of ferritin (257.2 ± 291.8 vs. 429.1 ± 410.8 mg/L, p=0.27), hemoglobin (10.0 ± 1.9 vs. 9.4 ± 1.7 mg/dL, p=0.45) and hematocrit (27.4 ± 8.3 vs. 27.0 ± 5.3 %, p=0.89). No difference was also observed in sleep architecture and number of events of increase in penile tumescence, both in non rapid eye movement (non REM) and REM sleep (21.9 ± 6.8 vs. 18.2 ± 7.6, p=0.17 and 7.5 ± 3.3 vs. 8.3 ± 5.0, p=0.59, respectively). Coincidence of these events with apnea-hypopnea, desaturation and periodic leg movement (PLM) events in non REM sleep was greater in SCA patients with priapism than in those without it (16.9 ± 11.1 vs. 7.9 ± 7.1, respectively, p=0.01). PLM index was increased in both groups, particularly in SCA patients with priapism (16.1 ± 16.2 vs. 5.7 ± 5.4 /h, p= 0.03) and associated with restless leg syndrome (88.2 vs. 50.0 %, respectively, p=0.02). Desaturation index was also higher in priapism group, in comparison to non-priapism (12.7 ± 8.8 vs. 7.6 ± 3.6 /h, respectively, p=0.05), as well as apnea hypopnea index (12.2 ± 11.0 vs. 5.5 ± 4.5 /h, respectively, p=0.04).

Compared to the group without priapism, SCA patients with priapism presented increase in apnea hypopnea index, PLM indexes during sleep and also association of increase in penile tumescence with respiratory events and PLM during non REM sleep. Our findings reinforce the literature data which highlights the link between disordered sleep and vaso-occlusive events in SCA. Moreover, the high frequency of PLM in SCA patients could be related to lower hepcidin levels recently observed in both SCA and restless legs syndrome.

FAPESP CEPID 98/14303-3 and AFIP.

No relevant conflicts of interest to declare.