Smokers' melanosis in a Nigerian population: a preliminary study.

AIM: Terms relating to pigmentation of the oral mucosa include physiologic (racial) pigmentation, oral pigmented nevi, oral melanotic maculae, melanoma, and smokers' melanosis. The literature is replete with studies about oral mucosal pigmentation which is thought to result from melanin incontinence. The documented etiological factors are both local and systemic and include hormones, drugs, smoking, and idiopathic causes. This study investigated the prevalence of melanosis among Nigerian smokers and controls who were non-smokers.

METHODS AND MATERIALS: A total of 1270 sites were examined in 253 subjects consisting of 60 smokers and 193 non-smokers. They were all systemically healthy adults drawn from 12 factories located in different urban and rural settings in the state of Lagos in Nigeria. Five oral mucosal sites were examined per subject. A single examiner performed all examinations and recorded all findings. Pigmentation was scored either as "present" or "absent." Subjects' smoking status, degree, and duration of smoking were ascertained and recorded using an examiner-administered questionnaire.

RESULTS: There were five pigmented sites (0.52%) among non-smokers and 18 (6%) among smokers. The buccal mucosa was the most frequently pigmented site found in smokers while the lingual mucosa was the most common site found for non-smokers. The prevalence of pigmented sites increased directly among smokers with the duration of smoking (years); degree of smoking (cigarettes smoked per day); and smoking pack-years (degree of smoking divided by 20 and multiplied by duration of smoking, where 20 is the average number of cigarettes in a pack of cigarettes). SPSS version 11.0 was used for data entry and analysis. Frequency distributions were generated for all categorical variables for descriptive aspects of the analysis. Means were determined for quantitative variables such as age and number of cigarettes smoked. For homogenous variances, the student's t test was used for quantitative variables between smokers and non-smokers, while for non-homogenous variances the Mann-Whitney test was adopted. Chi-square statistic was used for comparisons between smokers and non-smokers. In tables with low expected frequencies, Fisher's exact test was adopted. Statistical tests yielding p-values = or <0.5 were considered significant.

CONCLUSIONS: Smokers in this study had a significantly higher prevalence of pigmented oral mucosal sites (melanosis) than non-smokers. The number of pigmented sites increased with the degree and duration of smoking. The buccal mucosa was the most frequently pigmented site found among the smokers in this study.