Metabolic syndrome is related to polyneuropathy and impaired peripheral nerve function: a prospective population-based cohort study

Objective Diabetes mellitus is a known risk factor for polyneuropathy, but the role of pre-diabetes and metabolic syndrome remains unclear. We aimed to investigate the role of these factors in a communitydwelling middle-aged and elderly population. Methods 1256 participants of the population-based Rotterdam Study (mean age 70.0, 54.5% females) were screened for polyneuropathy with a questionnaire, neurological examination and nerve conduction studies. Data on type 2 diabetes and components of metabolic syndrome were also collected. Logistic regression was used to investigate associations of diabetes, pre-diabetes and metabolic syndrome and its separate components with polyneuropathy. Linear regression was used to investigate associations with nerve conduction parameters in participants without polyneuropathy. Findings Diabetes was associated with polyneuropathy (OR 3.01, 95% CI 1.60 to 5.65), while impaired fasting glucose was not (OR 1.55, 95% CI 0.70 to 3.44). Metabolic syndrome was associated with polyneuropathy (OR 1.92, 95% CI 1.09 to 3.38), with a stronger association when more components of the syndrome were present. Analysing separate components of metabolic syndrome revealed associations for elevated waist circumference (OR 2.84, 95% CI 1.35 to 5.99) and elevated triglycerides (OR 2.01, 95% CI 1.11 to 3.62). Similar associations were found after excluding participants with diabetes. In participants without polyneuropathy, metabolic syndrome associated with lower sural sensory nerve action potential amplitudes. Conclusions Metabolic syndrome, abdominal obesity and dyslipidaemia, are strongly associated with polyneuropathy, irrespective of the presence of diabetes. Metabolic syndrome also associates with impaired nerve function in people without polyneuropathy. Our study therefore suggests that cardiometabolic disturbances have an impact on peripheral nerve function that extends beyond clinically manifest disease.