Background <p>Periodic limb movements during sleep (PLMS) and obstructive sleep apnea syndrome (OSAS) are common sleep disorders that affect sleep quality. Their combined impact on sleep architecture and overall sleep disruption remains uncertain.</p> Objective <p>Assess whether the presence of comorbid OSAS in patients with PLMD further affects sleep efficiency and architecture compared to patients with PLMD alone.</p> Methods <p>A descriptive, comparative cross-sectional study was conducted on 70 patients diagnosed with PLMD (periodic limb movement index &gt; 15/h), identified through polysomnographic (PSG) recordings (Levels 1 and 2) between January 2021 to June 2023 at the Sleep Laboratory of the Hospital Universitário de São João, Porto, Portugal. Patients were divided into two groups: Group 1 (<i>n</i> = 52) with concomitant OSAS and PLMD, and Group 2 (<i>n</i> = 18) with PLMD alone. Demographic, clinical, and polysomnographic data were analyzed. Between-group comparisons were performed using appropriate statistical tests, with a significance threshold of <i>p</i> &lt; 0.05.</p> Results <p>No statistically significant differences were observed in sleep efficiency (<i>p</i> = 0.16), total sleep time (<i>p</i> = 0.42), or PLMS index (<i>p</i> = 0.98) between groups. However, significant differences (<i>p</i> &lt; 0,001) were observed in the apnea–hypopnea index, oxygen desaturation index, and respiratory arousal index. These findings suggest that OSAS does not exacerbate sleep fragmentation or reduce sleep efficiency beyond the disruption attributed to PLMS alone.</p> Conclusion <p>The presence of OSAS in patients with PLMD does not significantly worsen sleep fragmentation, efficiency, or architecture beyond the disruption caused by PLMD alone. Targeted therapeutic strategies should focus on managing PLMS-related disturbances independently of OSAS coexistence.</p> Graphical abstract <p></p>