There was no significant difference in the mean age or level of education among the SZ patients compared with their brothers (). Significantly more SZ participants were single or separated (p=0.04). SZ participants were also more likely to be unemployed (p=0.0001) and less likely to be living independently (p=0.0001). Modified mini mental state examination (MMSE) scores of the brothers were significantly higher than the SZ patients (t=65.643, p<0.001). Sociocultural factors were compared between schizophrenia subjects and their male siblings. Most subjects were Hindus (84%), followed by Muslims (11%), Sikh (4%) and Christian (1%). Three fourths (77%) subjects depended on family members or relatives for housing where as brothers resided independently on their own (54%) (p<0.001).Unemployment was more prevalent in subjects with schizophrenia (54%) while majority of their brothers (86%) were employed now and in the past. The difference was highly significant (p<0.001)().
Socio-demographic characteristics and prevalence of tobacco use
Comparison of patients & brothers who ever or never used tobacco
The proportion of SZ patients who had consumed tobacco in the past, or were currently consuming tobacco did not differ significantly from their siblings (). We compared current tobacco users between brothers and patients using chi-square. Patients with schizophrenia showed a lower rate (trend) than their brothers (Chi-square=3.5, p=0.06).
There was no significant difference on age and education between current users and non users in the pooled data (t-test). Among current users there was no significant difference between patients and brothers on marital status. All except one brother were employed while 50% of patients were employed. There was no significant difference between current user patients and their brothers on age and education. There was no significant difference between patients and their brothers on living arrangement among current smokers which suggests that living arrangement was not associated with smoking status. In addition almost all current smoker brothers were employed but 50% of patients were unemployed which suggests that smoking was not related to socioeconomic status. It may be a possibility that those patients who stayed with parents might get money for smoking from parents.
The Fagerstrom scores for smoked or smokeless forms of tobacco were similar among SZ patients and their siblings who currently used nicotine, though the age at initiation of tobacco use was significantly earlier among SZ patients (22.79±4.69 years vs. 24.44±3.58 years; t=2.013, p<0.001)(). There were 34 current users among the SZ patients and 47 among their brothers. The majority of patients and their brothers smoked tobacco (56.2% vs. 50.9%); fewer used smokeless forms (20.8% vs. 23.6%, respectively). Some consumed tobacco in both forms (22.9% of SZ patients and 25.4% of the siblings). Among SZ patients, 13 out of 28 smokers (46.4%) while among their brothers, 12/35 smokers (34.2%) were dependent on nicotine by DSM IV criteria, but the difference was not statistically significant. Among SZ smokeless tobacco users, 7 out of 13 (53.84%) were dependent, whereas 14 out of 28 brothers were dependent (not statistically significant).
Characteristics of current tobacco users
We compared SZ patients who had never used tobacco, with those who had consumed tobacco in the past or were currently using it (). The mean Scale for Assessment for Positive Symptoms scores of SZ patients who ever used tobacco were significantly higher than among non-users (t=-3.519, p<0.001)(). There was no significant difference between users and non-users with regard to Scale for Assessment for Negative Symptoms scores, age at onset of SZ or duration of illness. Mean modified MMSE scores were significantly lower among tobacco users than among non-tobacco using patients (mean±SD: 22.40±5.04 vs. 24.75±5.32, p=0.026). Among patients who completed the CNB (n=48), there were 19 tobacco users based on FTND scores (nicotine dependent, n=13). When nicotine dependent patients were compared with non-dependent patients with regard to CNB data, the former scored significantly worse than the latter with regard to accuracy and efficiency indices for attention (Z=-3.092, p=0.001 and Z=-2.84, p=0.003, respectively, ). Since there was significant difference on SAPS between tobacco users and non users we adjusted CNB scores with total SAPS scores. Tobacco users were significantly worse than non users on working memory speed (Z=-2.147, p=0.032). There were no significant differences with regard to the other cognitive domains.
Cognitive domains assessed using the Penn CNB among patients. CNB: Penn's Computerized Neurocognitive Battery.
We also compared siblings who had ever used nicotine with those who never used it. Most of the brothers in the non-user group were aged less than 30 years (53%), were students (24.4%) and most of them were dependent on family support (55.5%). The mean years of education among tobacco using siblings was significantly lower than non-users (8.93±4.01 vs. 11.38±3.08, t=3.36, p=0.001). Most of the brothers were employed, but overall employment rates were higher among the tobacco using brothers (96.3% vs. 73.3%). SZ patients were more likely to be dependent (77%) on relatives for residence, food and other basic needs in comparison to brothers (46%) who were mostly self-supported (χ2=20.294, p<0.001, df 1).