General practitioners' prescribing data for multiple sclerosis patients indicates a link with asthma.

Sir, The General Practice Morbidity Database Project (GPMDP) collates data routinely entered into GPs' computer systems for a representative sample of at least 10% of the resident population of Wales. 1 Anonymised data for 1996 was obtained for all patients from 24 GP practices in the database (n = 234 961 for 1996) who had a Read code of multiple sclerosis (MS) at some point from 1993 to 1996 as well as a randomly selected age–sex matched control group. Some 216 MS patients were identified, giving a prevalence of 91.9 per 105 (within the 24 GP practices' population in 1996). Their mean age was 46.7 years (range 17–84) and 67% were female. MS patients were found to have been prescribed significantly more (different) drugs (BNF categories 1–15) compared with controls (mean of 15.0 versus 8.0 respectively; P<0.0005) (Table 1). They were prescribed significantly more laxatives, diuretics, hypnotics and anxi-olytics, antidepressants, antiepileptics (including carbamazepine), corticos-teroids, drugs for genitourinary disorders (predominately oxybutynin), nutrition and blood (mainly vitamin B 12 and vitamin B compound), and neuromuscular disorders (primarily baclofen) (P<0.05). There were no significant differences between MS and control patients for analgesics and non-steroidal anti-inflammatory drugs (P>0.05). In contrast, significantly fewer bronchodilators and inhaled corticos-teroids were prescribed (P = 0.008 and P = 0.03 respectively). Patients with MS were also less likely to have a Read code for asthma (from 1993 to 1996) compared with controls (six versus 30 patients respectively; χ 2 = 16.03; P = 0.00006; odds ratio = 0.18; 95% CI = 0.47–0.67). Underdiagnosis and underprescribing for co-morbidities in patients with chronic diseases is well recognised. 2 However, this does not explain the low prescribing of drugs and low recording of Read codes for asthma in our MS population, since no underprescribing was found in other diseases , such as cardiovascular disease. MS patients may be less likely to develop asthma for several reasons. First, they may have less exposure to environmental aller-gens, particularly if housebound, although this could increase exposure to other aller-gens (e.g. house-dust mites). Secondly, reduced exercise owing to disability may limit exercise-induced bronchospasm, although intrinsic asthma only accounts for a minority of asthma cases. Thirdly, greater use of immunomodulatory drugs in MS patients may have alleviated asthma symptoms ; for example, two patients had cyto-toxic immunosupressants in 1996 and 22 (10.2%) had at least one course of corticos-teroids, although only one person had received a Read …