PubMed · 2672123
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R Arriagada, A Auquier. 1989. Difficulties in evaluating non-randomized studies.. https://doi.org/10.1016/0167-8140(89)90099-6
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Inference based on large sample results can be highly inaccurate if applied to logistic regression with small data sets. Furthermore, maximum likelihood estimates for the regression parameters will on occasion not exist, and large sample results will be invalid. Exact conditional logistic regression is an alternative that can be used whether or not maximum likelihood estimates exist, but can be overly conservative. This approach also requires grouping the values of continuous variables corresponding to nuisance parameters, and inference can depend on how this is done. A simple permutation test of the hypothesis that a regression parameter is zero can overcome these limitations. The variable of interest is replaced by the residuals from a linear regression of it on all other independent variables. Logistic regressions are then done for permutations of these residuals, and a p-value is computed by comparing the resulting likelihood ratio statistics to the original observed value. Simulations of binary outcome data with two independent variables that have binary or lognormal distributions yield the following results: (a) in small data sets consisting of 20 observations, type I error is well-controlled by the permutation test, but poorly controlled by the asymptotic likelihood ratio test; (b) in large data sets consisting of 1000 observations, performance of the permutation test appears equivalent to that of the asymptotic test; and (c) in small data sets, the p-value for the permutation test is usually similar to the mid-p-value for exact conditional logistic regression.
Patients suffering from schizophrenia are known to show an increased prevalence of nicotine addiction. The aim of this paper is to elucidate the relationship between schizophrenia and (chronic) use of nicotine. Nicotine seems to improve cognitive functions critically affected in schizophrenia, in particular sustained attention, focused attention, working memory, short-term memory, and recognition memory. Furthermore, several studies using evoked potentials (P50 paradigm) and prepulse inhibition of the acoustic startle reflex suggest that deficient preattentive information processing, a core feature of schizophrenia illness, is improved following treatment with nicotine. Smoking can also improve extrapyramidal secondary effects of antipsychotic medication and it induces cytochrome P4501A2, an enzyme system involved in the metabolism of several antipsychotics. There is substantial evidence that nicotine could be used by patients with schizophrenia as a "self-medication" to improve deficits in attention, cognition, and information processing and to reduce side effects of antipsychotic medication. Possible pharmacotherapeutic approaches for the regulation of abnormal neurotransmission at nicotinic acetylcholine receptors are discussed.
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