Impact of lifestyle on circadian orientation and sleep behaviour

Individual variability in preferred sleep timing is popularly described as chronotype. This study was conducted on 2105 subjects living in remote (500; without electricity), rural (500; with electricity) and urban areas (1105) having access to modern amenities of Chhattisgarh, India. Horne Ostberg questionnaires were used to find out the prevalence of morningness/eveningness. Sleep parameters and excessive daytime sleepiness were also evaluated with the help of questionnaires and the Epworth sleepiness scale. According to the Horne and Ostberg classification, 83.87% of the total population was classified as morning type (MT), 13.30% as intermediate type (IT) and 3.23% people were reported as evening type (ET) with a significant difference (P < 0.001) in distribution of chronotype. The frequencies of MT people in remote, rural and urban areas were 99.60%, 95.20%, and 71.58%, respectively. An increasing trend in the percentage of IT peoples was observed from remote (0.4%) to rural (4.8%) and urban areas (22.3%). This decreasing frequency of MT and increasing number of IT among urban inhabitants may be attributable to change of lifestyle. Significant positive correlations were observed between evening type and delayed bed/wake-up time, increase in sleep dissatisfaction and higher level of daytime sleepiness (P < 0.01). Elevated level of salivary C-reactive protein and decreased sleep duration was also observed in evening types. From the results of the present study it can be concluded that the prevalence of chronotypes in the general population is influenced by lifestyle, and that sleep disruption is more profound in evening-active people.