Marked increase in severe neurological disorders after nitrous oxide abuse: a retrospective study in the Greater Paris area

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Background Recreational nitrous oxide (N 2 O) use has become more widespread worldwide, leading to an increase in myelopathies and peripheral neuropathies. The aim of this study was to describe clinical and socioeconomical characteristics of severe N 2 O-induced (NI) neurological disorders (NI-NDs), to determine its incidence in the Greater Paris area and to compare it with that of similar inflammatory neurological disorders. Methods We performed a retrospective multicentric cohort study of all adult patients with severe NI-NDs in the neurology and general internal medicine departments of the Greater Paris area from 2018 to 2021. The incidence was compared with that of non-NI-myelitis and Guillain–Barré syndrome (GBS) using a sample of 91,000 hospitalized patients sourced from health insurance data. Results Among 181 patients, 25% had myelopathy, 37% had peripheral neuropathy and 38% had mixed disease. Most were aged between 20 and 25 years, lived in socially disadvantaged urban areas, and exhibited high rates of unemployment (37%). The incidence of NI-NDs increased during 2020 and reached a peak mid-2021. The 2021 incidence in 20–25-year-olds was 6.15 [4.72; 8.24] per 100,000 persons for NI-myelopathy and 7.48 [5.59; 9.37] for NI-peripheral neuropathy. This was significantly higher than for non-NI-myelitis (0.35 [0.02; 2.00]) and GBS (2.47 [0.64; 4.30]). The incidence of NI-NDs was two to three times higher in the most socially disadvantaged areas. Conclusion The recent increase in recreational N 2 O use has led to a rise in the incidence of severe NI-NDs, particularly in young adults with low socioeconomic status for whom NI-NDs strongly outweigh similar neurological disorders.