Subacute and chronic neuropsychological sequalae of acute organophosphate pesticide self-poisoning: a prospective cohort study from Sri Lanka

Abstract

Context

Some epidemiological evidence implicates acute organophosphate (OP) pesticide poisoning in long-term neurocognitive deficits. However, no study has prospectively followed up poisoned patients long-term from the time of intoxication. We aimed to determine whether clinically significant acute OP self-poisoning leads to subacute and chronic neurocognitive deficits, in a prospective follow up study.

Methods

Employing Mini Mental State Examination, Digit Span and Cambridge Neuropsychological Test Automated Battery (CANTAB), we compared multiple cognitive functions in 222 patients hospitalized with acute OP pesticide self-poisoning with a control group of 52 patients hospitalized with paracetamol overdose, at three time points: on discharge following clinical recovery, 6 weeks and 6 months post-ingestion. Intergroup comparisons at each time point were done in multiple regression models, adjusting for sex, age, education and psychiatric comorbidities. OP within-group analysis was done to determine a dose–response relationship.

Results

After adjusting for covariates, the OP poisoned group had significantly poorer working memory (Digit Span) and episodic memory (CANTAB Paired Associates Learning); impaired spatial planning (CANTAB Stocking of Cambridge); and slower response speed in the sustained attention task (CANTAB Rapid Visual Information Processing), in the post-discharge assessment. Only working memory and episodic memory measures were impaired in the OP group at 6 weeks, whereas no significant intergroup differences were observed at 6 months. The OP subgroup who had complete red cell acetylcholinesterase inhibition on admission had poorer episodic memory when tested post-discharge than those who had partial inhibition, but no significant subgroup differences were observed at 6 weeks or 6 months.

Discussion

Acute OP pesticide poisoning may cause neuropsychological impairment that outlasts the cholinergic phase on a subacute time scale; but does not cause measurable chronic neuropsychological deficits.

Keywords:

• Organophosphate
• pesticide
• poisoning
• cognition
• memory
• neuropsychological effects
• self-harm

Acknowledgements

The authors thank the physicians-in-charge of the Toxicology Departments of the Teaching Hospital Peradeniya and the District General Hospital Nuwara Eliya, doctors Kamal Naser, Ajith Gurusinghe, Upul Vidanapathirana. The authors also thank doctors Noorul Ikram, Mohommed Azam, Udayaprashanth Gnanaseharan and Husain Ameen who assisted in data collection.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was supported by the Australian National Health and Medical Research Council grant [1030069] through South Asian Clinical Toxicology Research Collaboration, University of Peradeniya.