Pars Cohort Study

Setting of the Study

The district of Valashahr has an area of 1,650 km2 and over 40,000 inhabitants mainly of Fars or Turk ethnicities and sparsely of other ethnicities. The district consists of 5 counties and the city of Valashahr. There are 5 health centers in the area supervising 31 health houses and covering a total of 93 villages. Each health house is staffed by 2 community health workers named “Behvarz”. These community health workers were originally responsible for vaccination, family planning, recording vital horoscopes, and primary health care mainly for communicable diseases. However, they have been trained to participate in the conduct of the study.

The participants in this study consisted of all eligible people, both healthy and unhealthy in Valashahr and the nearby villages. All residents of the district between 40 and 75 years old were invited. The only exclusion criteria were unwillingness to participate or being a temporary resident. The participation rate was 95%. A total of 9,264 subjects visited the Pars Cohort Study Center (PCSC) for interview and physical examination, and provided biological samples. The response rate was higher among the rural inhabitants, which is explained by the proximity of their workplace to their residence in agricultural occupations, and their flexible working hours.

The list of participants with their cell phone numbers and/or telephone numbers were acquired through 31 health houses in the region. Then, based on the catchment area of health houses, the district was divided into sub-regions.

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Non-communicable diseases (NCDs) comprised 57% of all deaths at global scale in 1990, which increased to 70% in 2013. Ischemic heart disease and cerebrovascular accidents were the top causes of death in 2013 across the globe. The share of NCDs in global disability (in terms of years of life lost due to disability) as well has increased from 76% in 1990 to 82% in 2013.

In Iran, ischemic heart disease was the first cause of death and stroke was the 5th cause in 2013. Overall, 236 thousand deaths were reported in Iran in 2013, out of which about 57% were caused by circulatory diseases and about 17% by cancers. There was a sharp increase in prevalent cases from 1990 to 2013.

At sub-national level, there are sparse population-based studies on prevalence of main NCDs and their risk factors. Apart from the cross-sectional prevalence, investigating the trend and prognosis of NCDs and their risk factors is mandatory as well, which can only be done within the setting of prospective studies. The results of very few population-based longitudinal studies in Iran have revealed high prevalence of CVDs and metabolic diseases in both urban and rural areas. Unhealthy diet, overweight and obesity, high blood pressure, high blood glucose, and high cholesterol are the major risk factors of CVDs. The prevalence of metabolic syndrome reported among adult participants in these studies has been very high.

To the best of our knowledge, no population-based prospective study on NCDs has been established in South of Iran so far. PARS cohort study (PCS) was established in 2012. The methods of baseline data definition and collection and follow-up methods have been largely adopted from Golestan Cohort Study. Similarly, interventional studies are designed to investigate the cost-effectiveness of Polypill and the predictive performance of clinical and imaging risk scores. PARS cohort study can be a platform for further nested case-control studies and trials and also for strengthening the research network in the area.