The relationship between rotating schedules, demographical factors, and dyslipidemia
Rotating schedule to cover different shifts is a common practice in many countries [1]. According to the available statistics, more than 20% of workers in industrial societies have a rotating schedule [2]. It is a rotating and unnatural work program in which workers have to work overnight based on a rotating schedule [34]. According to studies, rotating work schedule disrupts the natural circadian rhythm and it is responsible for many physical health problems [5]. The circadian rhythm is a 24hrs cycle that is found in many biochemical and physiological processes or behavior of living creatures on earth. It helps the body to adapt itself to the day-night cycle. The circadian rhythm is controlled by clock genes . These genes control production of proteins and the production rate increases or decreases following a specific rhythm. The biochemical signals regulate different activities like sleeping, resting, awaking, daytime activities, body temperature, cardiac activity, hormone secretion, blood temperature, oxygen intake, and metabolism [5, 6]. Therefore, long term interruption of circadian rhythm caused by a rotating schedule may lead to a set of disorders such as insomnia, obesity, and higher blood pressure, all which are the risk factors of cardiovascular diseases (CVDs) [5]. In fact, workers with rotating schedules are at a high risk of physical pressures and tensions, and this increases the disorder of circadian rhythm and diseases like CVDs, coronary heart diseases (CHDs), hypertension, diabetes type 2, and digestive, genital, musculoskeletal, and mental diseases [7, 8]. The main function of the circadian system is to control metabolic and physiological reactions [5], which in return affect nutritional habits and lipid and carbohydrate metabolism [9, 10]. Dyslipidemia is a state of abnormal increase in lipid level in the plasma, that under the effect of a rotating schedule may lead to a wide range of lipid disorder [6]. Based on the available definitions, dyslipidemia is diagnosed through checking the increase in the level of cholesterol, triglyceride, low-density lipoprotein and decrease in the level of high-density lipoprotein. The lipid disorder is categorized into two groups namely 1- primary dyslipidemia (caused by genetic disorder in lipoprotein metabolism) and 2- secondary dyslipidemia caused by changes in the metabolism of lipoprotein [11, 12]. It is proven that dyslipidemia is a cause of CHDs, atherosclerosis, myocardial infarction, cerebrovascular accident (CVA), and death [13]. The complication is responsible for the death of 2.6 million and debilitation of 29.7 million individuals every year [14]. Examination of lipid disorder outcomes in Thailand showed that in 2009 based on a national census, the prevalence of dyslipidemia was 66.5% [14]. A meta-analysis systematic review in Iran showed that the prevalence of abnormal cholesterol level, TG, LDL, low HDL, and prevalence of dyslipidemia in Iran was alarming [6]. Given the effects of rotating schedule on lipid disorders and the increase in the prevalence of CHDs or CVDs and taking into account the paucity of studies on this field, the present study is an attempt to examine the relationship between rotating schedule, demographical factors, and prevalence of dyslipidemia in workers of petrochemical plant in the southwest of Iran.