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

Abstract

Background: Recreational nitrous oxide (N₂O) 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 N₂O-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 N₂O 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.

Keywords: Epidemiology; Myelopathy; Nitrous oxyde abuse; Peripheral neuropathy.

Fig. 1

Incidence of N₂O-related neurological disorders in the Greater Paris area during the period 2019–2021. The first cases reported date from 2019, then an increase in cases is observed with a peak in 2021

Fig. 2

Distribution of cases by household income in Paris and inner suburbs. The majority of cases are located in lower income areas of the inner suburbs

Fig. 3

Age-specific incidence of NI and non-NI neurological disorders. There is a significantly higher incidence of neurological complications in individuals under the age of 25 following N₂O intoxication compared with similar disorders: NI peripheral neuropathy and GBS (left panel), and NI/non-NI myelopathy (right panel). Abbreviation: GBS Guillain–Barré syndrome, NI N₂O-induced