Abstract Background: Recently, the appearance of beta-amyloid precursor protein (APP) has been demonstrated in the neonatal brain following hypoxic–ischaemic injury. As chronic hypoxia is one of the favoured theories of causation in the sudden infant death syndrome (SIDS), the correlation between APP in the brainstem and sleep apnea in SIDS was investigated. Materials and methods: Among 27,000 infants studied prospectively to characterize their sleep–wake behavior, 38 infants died under 6 months of age, which included 26 cases of SIDS. All the infants had been recorded during one night in a pediatric sleep laboratory, some 3–12 weeks before death. The frequency and duration of sleep apnea were analyzed. The brainstem material was collected and immunohistochemistry with anti-Alzheimer precursor protein A4 (APP) was carried out. The density of APP-positive elements was measured semi-quantitatively. Correlation analyses were carried out between the density of APP-positive elements and the data on sleep apnea. Results: No correlation was found. Conclusion: No correlation between pathological data of APP and physiological data of sleep apnea was not in agreement with the association of sleep apnea in pathophysiology of SIDS.