Objective: Despite higher smoking rates in schizophrenia, few studies have explored the clinical-demographic correlates of different amounts of smoking exposure. Little is known about the association between smoking severity and clinical phenotypes in Chinese patients with schizophrenia.
Materials and methods: We investigated differences between heavy (≥1 pack/day) and non-heavy (<1 pack/day) smoking in 550 male inpatients with schizophrenia using clinician-administered questionnaires and the Fagerstrom Test for Nicotine Dependence. They also were rated on the Positive and Negative Symptom Scale (PANSS), the Simpson and Angus Extrapyramidal Symptom Rating Scale (SAES), and the Abnormal Involuntary Movement Scale (AIMS), as well as were assayed with laboratory tests and an electrocardiogram.
Results: Heavy smoking prevalence was approximately 31 %. Compared to the non-heavy smokers, the heavy smokers were younger, more with paranoid subtype but less with disorganized subtype schizophrenia, smoked at an earlier age, fewer getting clozapine or all atypical antipsychotics together, and were taking larger doses of antipsychotic drugs. The heavy smokers scored significantly lower on the PANSS negative symptom subscore and total score, and also on the SAES and AIMS scores than the non-heavy smokers. In addition, heavy smokers displayed longer rate-corrected electrocardiographic QT intervals, but without any significant differences in other laboratory tests.
Conclusion: Our results suggest several clinical or demographic differences between the heavy and non-heavy smoking patients with schizophrenia in a Chinese population. Heavy smoking remains a general health risk for schizophrenia.