Impact of smoking hookah and bidi on global DNA methylation: a community-based study from Haryana, North India

Abstract Smoking is a major contributor to the increased burden of chronic diseases worldwide. Smoking has been reported to be associated with several adverse epigenetic modifications like altered DNA methylation patterns. Despite adverse effects, smoking hookah and bidi is accepted as a cultural practice in several communities, viz., the Jats of Haryana. This study aims to explore the smoking-induced alterations in global DNA methylation in the Jat community, where smoking is a cultural practice. A total of 1075 participants, aged 30–75 years (69.8%, females), belonging to the Jat community from Palwal, Haryana, were recruited. Data on socio-demographic and lifestyle variables were collected through pre-tested interview schedules. The ELISA-based colorimetric technique was used for performing peripheral blood leucocyte global DNA methylation. The difference between median global DNA methylation (5mC%) levels of non-smokers (median 5mC% = 0.66) and smokers (median 5mC% = 0.62) was not found to be statistically significant (p value = 0.309). However, the median 5mC level among former smokers (median 5mC% = 0.41) was found to be significantly lower than smokers and non-smokers (p value < 0.01). The adjusted regression model revealed former smoker status to be significantly associated with global DNA hypomethylation. Further, no significant difference in global DNA methylation levels was found between heavy and light smokers. The study suggests that continuous exposure to tobacco smoke during the prenatal and later stages of life may be contributing to the new environmental adaptations resulting in no significant effect of smoking on epigenetic alterations. A unique DNA hypomethylation signature of former smokers may be due to smoking-related comorbidities.