Risk factors of oral candidosis: A twofold approach of study by fuzzy logic and traditional statistic

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Abstract

Objective

To assess a panel of risk factors associated to oral candidosis (OC) onset and its chronic maintenance by means of fuzzy logic (FL) approach and statistical traditional methodology (STM); to investigate their casual relationship within a multifactorial framework.

Design

Case–control study.

Setting

One hospital-based clinic.

Patients

Eighty-nine patients with OC infection microbiologically diagnosed and 98 healthy subjects were consecutively recruited.

Outcome measurements

Anamnestic and clinical evaluations for OC, microbiological assessment (i.e. culture, CFU/mL counting and identification) were performed. The commonest predisposing factors for OC onset and its chronic status were analysed by FL and STM.

Results

By means of a twofold analysis (FL and STM) significant associations between OC onset and its chronic maintenance were found with respect to denture wearing and hyposalivation/xerostomia, as local risk factors, and to age and female gender, as socio-demographical variables. Tobacco smoking was found not to be a risk factor.

Conclusions

The twofold (FL and STM) statistical approach for the identification of OC risk factors has been found useful and accurate in individuating a more selected target population for OC onset and chronic maintenance. The target patient appears to be an elderly person with multiple disease inducing, directly or by medications, hyposalivation/xerostomia. This data could provide to general and dental practitioners a decision-making model finalised to their preventative strategies for the geriatric population.

Introduction

Oral candidosis (OC) is a common opportunistic infectious disease. The predisposition to oral candidal colonisation and infection is increased with xerostomia,1 immunodeficiency,2, 3, 4, 5, 6 denture wearing7, 8 and tobacco smoking.9 In addition, it has been suggested that high carbohydrate diet10, 11 and diabetes mellitus12, 13, 14 may predispose to OC, although there is conflicting data, particularly on the former.

There is a likelihood that more people will be at risk of OC as a consequence of increasing lifespan, greater use of immunosuppressive therapies and the wider range of drugs that can give rise to hyposalivation/xerostomia.15, 16 For example, the prevalence of diabetes mellitus and hypertension is increasing in the developed countries, and 88% of people over 65 years of age receive multiple medications. In addition, the number of patients receiving immunosuppressive therapy (e.g. following allograft transplants or autoimmune diseases) has risen considerably in the last decade.17 In view of these changes, there is a need to establish more specifically a target of people at risk of OC in order to create for them an appropriate preventive program.

Until now, the association between the several risk factors for OC, above mentioned, and its development and/or chronic maintenance has been widely conducted only by statistical traditional methodology (Aristotelian logic).18, 19, 20, 21, 22, 23 Nevertheless, this approach could have any limits, above all which one related to impossibility to consider intermediate logical value. Consequently the analysis of the non-linear links and complex interactions between multiple variables under study result extremely complicated.24 In order to surpass these restrictions it should be possible to utilise a twofold approach of study by fuzzy logic (FL) and statistical traditional methodology (STM).

FL is a superset of conventional (Boolean) logic introduced by Zadeh in the 1960s as a means to model the uncertainty within natural language.25, 26 Subsequently, fuzzy theory has been applied in several fields, especially in medical applications.27, 28, 29, 30, 31 It is based on theory that the description of a decision in terms of “more…less” is more adequate to real problems than by keen “yes–no” degree and it is not surprising that the first reported using was just in medical investigation.32 Hudson et al., analysing different source of uncertainty in medical decision making, concluded that FL could afford an efficient approach to solve medical problems especially when a complex interactions between the factors under study is present.33 In fact, the important advantage of this analytic method in comparison with classical statistical models, is the capacity to handle, at the same time, a very high number of variables notwithstanding the fact that these are not linearly connected. Therefore, in a framework in which several risk factors operate and need to be analysed simultaneously FL analysis might be a powerful tool for accurately detecting causal relationships, also in the field of infectious diseases.30, 31

The fuzzy neural network (FNN) is one of the most advanced artificial neural networks (ANNs) models, and its most attractive feature is that relationships between input and output variables can be described accurately from the acquired model.26 In the present study the input variables are the predisposing factors for OC, whereas the output variable is OC.

The aim of the present study was to verify the most commonly reported risk factors for OC onset and its chronic status utilising a twofold approach of study by FL and STM.

Section snippets

Study design

A case–control study in a secondary hospital base (Department of Oral Sciences, Section of Oral Medicine, University of Palermo, Palermo, Italy) was undertaken. Between January 1999 and July 2001, 371 patients were referred to the above institution to confirm the clinical diagnosis of OC. The study group was composed of 89/371 patients [mean age 66 years (range 35–88 years), males 31 (34.8%), females 58 (65.2%), smoker 19 (21.3%) and non-smoker 70 (78.7%)] enrolled on the basis of these

Risk of OC

The first step was to evaluate the risk association of the socio-demographical variables (A, G, and S) with OC (binary outcome: present/absent) in the study group vs. controls. This stepwise was performed by means of FL and STM. After examination of the inference rules elaborated by FL, the OC risk was found to be higher in females than males, in both categories it increased with A (≥54 years) regardless of tobacco smoking (RMSE = 0.363, Accuracy = 0.80, Sensitivity = 0.79, Specificity = 0.81) (Fig. 2).

Discussion and conclusions

Oral candidosis is the most common opportunistic oral infection in human beings. Several predisposing factors have been recognised as potentially involved into the development and, above all, into the chronicity and/or relapse of this infection (age, tobacco smoking, hyposalivation/xerostomia, denture wearing, antibiotic and corticosteroid therapies, endocrine disorders, immunodeficiency and contemporary malignancy) and the analysis of their relationship has been widely conducted only by

Acknowledgements

The authors would like to thank Maria E. Milici (Department of Hygiene and Microbiology, University of Palermo, Italy) for the use of laboratory facilities and assistance in microbiological evaluation.

This work was supported in part by the Italian Ministry of University and Research (MIUR), Rome, Italy.

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