Cohort Profile: The Fasa Adults Cohort Study (FACS): a prospective study of non-communicable diseases risks

Why was the Fasa cohort set up?

Non-communicable diseases (NCDs) are the leading cause of death in the world and accounted for 71% of all deaths in the world in 2016. The most important NCDs for this mortality are cardiovascular diseases (44% of all NCD deaths and 31% of all global deaths), cancers (22% of all NCD deaths and 16% of all global deaths); chronic respiratory diseases (9% of all NCD deaths and 7% of all global deaths) and diabetes (4% of all NCD deaths and 3% of all global deaths). The global risk of death from one of the four major NCDs was 18% in 2016. This probability was higher for males than for females in all countries.¹

Approximately 80% of NCD deaths occur in low- and middle-income countries, and they are the most common cause of death in most North American and Eastern Mediterranean countries, Southeast Asia and Europe.² In all countries, regardless of their socioeconomic status, tobacco use, alcohol consumption, unhealthy diet including high salt and sodium intake, physical inactivity, overweight and obesity, high blood pressure, hyperlipidaemia and high blood sugar are the most important risk factors for NCDs. In Iran, as in other developing countries experiencing epidemiological transmission, NCDs have become the predominant causes of death.³ The solution to controlling the global epidemic of NCDs is to identify the most important and modifiable risk factors in each region and to prevent and control these risk factors.⁴ Limited reliable information on the distribution of risk factors for NCDs is an important concern in developed countries. This concern has received much attention in Iran for estimating risk factors and designing control programmes.^5,6

The Prospective Epidemiological Research Studies in IrAN (PERSIAN) Fasa Adult Cohort was launched at the Fasa University of Medical Sciences in March 2014. This study is being conducted in Sheshdeh and Qarabolagh districts in 24 villages, and includes a sample of 10 000 people aged 35–70 years.^7,8 The purpose of this study is to develop the existing knowledge on the evaluation of risk factors for non-communicable diseases, to prevent them by modifying or changing the risk factors that can be modified and to provide information to health policy makers.

Who is in the cohort?

Sample region

The prospective Fasa Adult Cohort study has 10 118 participants aged 35–70 years in Sheshdeh and Qarabolagh districts of Fasa city. Fasa city is located in the south of Fars province, with the coordinates of 28.55°N and 53.39°E in Iran. Fasa city has four central parts comprising Nobandagan, Sheshdeh, Qarabolagh and Shibkuh, with a population of 205 000 people. The city has a temperate semi-arid climate and three ethnicities: Persian, Arab and Turkish. This study started in 2014 in Sheshdeh and Qarabolagh wards with two towns and 22 villages. Up to the end of 2021 four follow-ups have been performed, and the reassessment phase began from September 2021 (Figure 1).

Sampling strategy

The study was conducted by the census method. The information on people living in the area was obtained from the health vice chancellors of the university, who also obtain their information from the population census register. The health worker (behvarz) in each village has complete information about the people of the area he or she covers, and cooperated with us in this cohort study. The inclusion criteria were that participants must be of Iranian nationality, have at least 1 year of residence in the area, and be 35 to 70 years old, willing to participate in the study and able to communicate verbally. Participants could also leave the study if they were not interested in continuing. Since the selection of the target area among the three suburbs of Fasa was random, and from the selected area, namely Sheshdeh and Qarabolagh, the samples were selected by census and not sampling, we expect this population to be representative of the entire population of Fasa.

Registration phase

The enrolment phase was from October 2014 to September 2016. First, the list of names of the people was obtained from the health workers of the Sheshdeh and Qarabolagh districts. People within the age range of 35–70 years (11 097 total population in that age range and 10 622 eligible to participate in the study) were the target population in the cohort. Individuals were selected based on inclusion criteria and invited to enter the study by telephone. People who refused to participate in the study after three phone calls were excluded from the study. An average of 25 people were enrolled and studied at the centre each day. Written consent was obtained from each participant and each was given a unique PERSIAN cohort identification number (cohort ID). Samples were then obtained from participants (10 118 recruited of 10 622 eligible; participation rate 95.2%) as follows.

Sampling and biobank

Blood, urine, hair and nail samples were taken from all participants. Individuals were instructed to fast for at least 8–12 h, not to colour their hair and nails for at least 3 months before sampling and to have long nails on the day of sampling. A 25-ml blood sample was collected from each participant. All samples received a code that included their unique cohort identification number (Table 1 summarizes the list of collected information). In order to encourage people to participate in the study, the initial results of routine tests are given to participants for consultation with their family physician.

To preserve and store these specimens, all samples were transferred to the Cohort Reference Laboratory located at the Fasa University of Medical Sciences. The samples are stored in freezers at -20°C (urine, hair and nail) or -70°C (blood, serum, plasma and buffy coat). The laboratory is equipped with an emergency power and a freezer temperature warning system. Laboratory personnel work in this laboratory on an on-call basis.

How is the cohort followed up?

Study participants are followed up annually by telephone about the incidence of target diseases such as cardiovascular disease, diabetes, cancer and chronic lung disease, as self-report of doctor-diagnosed conditions. If necessary, a specialist doctor examines them. In the first phase, the participation rate was 99.8%, in the second phase, 99.6%, in the third phase, 99.7% and in the fourth phase, by telephone, 99.8%, and in general, 99.0% in all four phases.

Reassessment phase of risk factors

Since September 2021 and the completion of the fourth follow-up, the cohort study has entered the re-evaluation phase of the same variables as the registration phase and is planned for 3000 of the participants in the first phase. The selection method for this phase of the study is random sampling. All of the steps taken and all clinical examinations performed, biological samples taken and questionnaires administered in the registration phase are included in the re-evaluation phase.

The study protocol has been previously published.⁷

What has been measured?

Study interviewers for this study were recruited from among the natives of the city and, after they had been interviewed and confirmed by the primary investigators of the Fasa cohort group, all the study interviewers were trained by the national cohort experts to administer the questionnaire. Interviewers were preferentially selected from among people with expertise in the field of the questionnaire they were administering. For example, nutritionists administered the nutrition questionnaire, and nurses administered the questionnaires relating to disease and medication.

To reduce measurement errors, all instruments used for the cohort, including anthropometric instruments, elecrocardiogram sphygmomanometers, and instruments used in the nutrition questionnaire (spoons, plates, scales, glasses) were periodically calibrated and evaluated. Also, the daily field supervisor was responsible for controlling the registration of individuals, monitoring the questioners, and all administrative problems in the field. Table 1 summarizes the questionnaires and variables that were collected at baseline.

In the follow-up phase, information was obtained via a phone call about the participants’ health status and occurrence of the desired outcomes. In cases such as death (from any cause) or occurrence of any disease (at any site), two external internists independently review all available clinical documents and allocate a disease code and a date of diagnosis of an NCD or death. The disease codes provided by the two internists are compared and if they are different a third, more senior internist reviews the data and makes the final decision on the code.

What has been found?

Of the 10 118 people aged 35 to 70 years included in the cohort, 4566 (45.1%) were men and 5552 (54.9%) were women. The average age of men and women was 48.6 ± 9.6 and 48.6 ± 9.5 years, respectively (P = 0.822). Most participants were married. Only 2.4% of the participants had an academic education and 25% were illiterate. Table 2 shows the basic characteristics of men and women who participated in this study.

Table 3 shows that the most common diseases among participants were hypertension (20%), kidney stones (17.2%), diabetes (12.3%), fatty liver disease (10.4%) and osteoporosis (9.8%). Diabetes, fatty liver disease, osteoporosis, rheumatic disease, gallstones, thyroid disease and hypertension were more common in women and ischaemic heart disease, myocardial infarction and kidney stones were more common in men.

Table 4 shows the 5-year incidence of diseases and death per 1000 population.

Since this study was designed to investigate the health problems in the region and to attempt to improve the health status of the people, from the moment of the end of the patient phase, the work to investigate the epidemiology of the diseases and existing risk factors started. The main problems in the area—heart diseases, blood pressure and diabetes—were evaluated and studies were set up to find the risk factors related to them. The results of these studies have been published in various articles, the list of which is available on the page of the Non-Communicable Diseases Research Center of Fasa University of Medical Sciences [http://ncdrc.fums.ac.ir, https://fa-ncdrc.fums.ac.ir]; this list is constantly updated. For example, studies were conducted on electrocardiogram parameters and their relationship with anthropometric indices,⁹ insufficient sleep¹⁰ and metabolic syndrome.¹¹ In other works, studies were conducted on blood pressure and factors related to it,¹² obesity¹³ and drug addiction¹⁴ which is one of the serious problems in the region.

What are the main strengths and weaknesses?

This study has some strengths. The large sample size is one of the strengths of the study, which makes it possible to test the hypotheses in this study with high power. Also, the participants were selected by census, and most eligible individuals were included in the study.

The population covered by the study had a rural lifestyle, and thus provides useful information about this population group. Unlike other cohorts in Iran that include the urban population, in this study, active communication is established with other components of the health system such as health workers and health care systems.

In this cohort, it is possible for researchers to work in various fields of public health and medicine. Another feature of this study is the existence of a biobank that can provide the basis for other studies such as nested case-control studies and case-cohort studies.

This study has two limitations. The collection of self-reported data and non-confirmation through communication with medical records or other information records was the most important limitation of the study. Another issue is that the target population is aged 35 to 70 years, so the results are not generalizable to all age groups.

Can I get hold of the data? Where can I find out more?

The data collected by Fasa Adult Cohort Study are not freely available but can be shared under conditions of collaboration. Collaborative research projects are encouraged and enquiries and queries can be submitted to [[email protected], [email protected], [email protected]]. Collaborative research projects will be discussed in the first instance, with the final decision on data sharing decided by the NonCommunicable Diseases Research Center (NCDRC) steering committee which will evaluate all proposals related to data sharing. For further information, please visit NCDRC website at [http://ncdrc.fums.ac.ir/].

Ethics approval

The study protocol, patient information sheet and consent forms were approved by the ethics committee of Fasa University of Medical Sciences (enrolment: IR.FUMS.REC.1394.3; follow-up: IR.FUMS.REC.1395.177).

Author contributions

R.M., H.P. and E.B. conceptualized the study. R.M., H.P., E.B., M.F. and R.H. designed the study. E.B., M.F., A.D. and R.H. directed the study's implementation. M.M.N., A.D. and M.S. performed data analysis. M.F., R.H. and M.K.V. interpreted the findings and drafted the manuscript. Y.M., M.F. and R.H. revised the manuscript for important intellectual content. All the authors have read and approved the final version of the manuscript.

Funding

The study was funded by Fasa University of Medical Sciences and supported by the Deputy for Research at the Iranian Ministry of Health. The research council of the university funded the study under grant no. 94058 and 95043.

Conflict of interest

The authors hereby affirm that the manuscript is original, that all statements asserted as facts are based on authors careful investigation and accuracy, that the manuscript has not been published in total or in part previously and has not been submitted or considered for publication in total or in part elsewhere. Each author acknowledges he/she has participated in the work in a substantive way and is prepared to take public responsibility for the work and authors have no competing interest to results of article.

References