Polyneuropathy and statins

Myopathy is a recognised risk associated with the use of lipid lowering drugs. In general practice in the UK one estimate is that the incidence of myopathy in users of lipid lowering drugs is 2.3 per 10,000 person years, with a relative risk compared with nonusers of 42 for fibrates and 8 for statins [1]. A new study [2] tells us that polyneuropathy is also likely to be a problem, and that it needs looking at the problem.

Study

This was conducted in a county of Denmark with a population of 465,000. Residents

have a civil registration number that is used in discharge prescription registries, so that it is possible to find all residents with a particular disorder, and find out what drugs they have been prescribed.

In a five-year period to the end of 1998, all patients with a discharge of polyneuropathy were examined. Some lived elsewhere, some were diagnosed before the study period, some had predisposing conditions (renal failure, diabetes, thyroid, and others had no proper diagnosis or were wrongly diagnosed. Clinical diagnostic features were distal symmetric sensory symptoms or symmetric motor symptoms and no upper motor neurone signs, or both. Neurophysiological criteria were abnormal conduction in two or more peripheral nerves, with at least one being a leg nerve.

A diagnosis of peripheral neuropathy was only accepted if both clinical and nerve conduction criteria were compatible with the diagnosis. Several levels of confidence were defined for idiopathic polyneuropathy (Table 1).

 

Table 1: Definition of diagnosis of polyneuropathy

Description	Definition
Definite	Adequate work up and tested for exclusion diagnoses and conditions, and no apparent cause of neuropathy established
Probable	Only sufficient information to rule out alcohol overuse, diabetes and renal insufficiency
Possible	Information not sufficient to ascertain presence or absence of any exclusion diagnosis

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