Prevalence of modifiable cardiovascular risk factors in Yazd inner-city municipalities

Yazd Health Study (YaHS) is a prospective cohort study conducted to determine the prevalence of non-communicable disease and related risk factors in the Yazd Greater Area (YGA), which is located in central Iran. The present study is a cross-sectional analysis of the Yazd Health Study (YaHS) recruitment phase data of YaHS is a prospective cohort study.

The historical city of Yazd is the capital of Yazd province (Iran) which was recognized as a World Heritage city by UNESCO in 2017. Yazd city is divided into 4 municipal districts and a special historical district (Fig. 1). Historical region (Yazd 5) and villages annexed to Yazd city accommodate a high proportion of immigrant residents, who are in lower socioeconomic class. These differences in social factors can affect the incidence and severity of heart disease risk factors.

Maximize sample size was calculated with prevalence of 50% and significance level 99%, for all the NCD and their risk factors. The initial sample size was calculated 538. It was corrected based on ten strata (20–29, 30–39, 40–49, 50–59, 60–69 by sex). We considered the design effect of 1.5, 5% non-response in recruitment phase (n = 8494) and 15% attrition rate or follow-up loss (n = 9768) in second wave. So, we decided to enroll 10,000 persons.

Ten thousand residents of YGA aged 20 to 69 years were selected using cluster random sampling method. 200 clusters were randomly selected based on participants’ residential postcode. Then, each cluster of 50 samples was divided into the following subgroups: 25 men and 25 women; five people in each sex in each ten-year age range categories (20–29, 30–39, 40–49, 50–59 and 60–69 years old). Trained interviewers completed a validated questionnaire and performed a physical examination (94.9% response rate). Sampling procedures and other details of the YaHS study have been published elsewhere [20]. Residents of Yazd annexed cities and rural areas were excluded from the analysis.Thus, 8749 individuals, who lived in five municipalities of Yazd city, were included in the final analysis.

To assess individual-level socioeconomic factors, self-reported information on education level, job status, health insurance, marital status, and migration status were recorded. The included cardiovascular risk factors were: T2DM (defined as history of diabetes mellitus and/or insulin drug therapy); dyslipidemia as defined by history and/or drug therapy for hypercholesterolemia; hypertension as defined by history of hypertension, a systolic blood pressure ≥ 140 mmHg and/or a diastolic blood pressure ≥ 90 mmHg and/or antihypertensive therapy [21] and d) overweight as defined by a body mass index (BMI) between 25 to 29.9 kg/m² and obesity (BMI of ≥30 kg/m2) [22]. Lifestyle cardiovascular risk factors were also analyzed, including current tobacco and/or hookah smoking and a selected unhealthy diet (Eating < 2 servings of fruits/day, Eating < 2 servings of vegetable/day, Eating > 4 servings of red meat/week, Eating < 1 serving of fish /week [23] and low physical activity according to IPAQ short form (SF) questionnaire. The IPAQ-SF examines the intensity of physical activity last week for different levels. Weekly walking time, moderate-intensity and intense activity severity were calculated individually. Estimate metabolic equivalent (MET; multiples of resting energy expenditure) by minutes reported per week in each category. Finally, participants were classified into three levels of “low”, “moderate” and “high” physical activity [24, 25].

All procedures performed in this study were approved by the ethics committee of Shahid Sadoughi University of Medical Science (IR.SSU.MEDICINE.1396.311) and informed consent was obtained from all participants.

In the population of Yazd, 95.4% of adults consume fish less than once a week and 23.2% eat red meat more than four times a week. Fruit and vegetable intake (less than twice a day) are seen in 53.2 and 77% of the individuals, respectively. An unhealthy eating pattern was present in 85.7% of Yazdi adults with a significant difference of 10% between urban and rural areas, indicating the impact of socioeconomic factors on health behaviors. The residents of region 3 had the highest percentage of fish, vegetables and fruit consumption compared to the other regions in the study area. Food habits influenced by a set of variables including food availability, preparation, socioeconomic status, local culture, religion, and media advertisement [26]. Health policymakers need to take into account these relationships in policy planning and interventions.

The prevalence of hypercholesterolemia in Yazd (16.7%) is lower than other studies in Iran (41.6%), Saudi Arabia (54%), Turkey (37.5%), and Europe (56.7%) and even less than the previous study in Yazd itself (35.4%), although consumption varies across Yazd regions [27, 28].

Reducing red meat consumption can be effective in decreasing the risk of CVD. Educational interventions; Physicians ‘and health care providers’ recommendations are one of the causes of changes in the consumption of fatty foods and the low prevalence of cholesterol in the community. Family income and food price changes, including red meat, can also contribute to household consumption.

The prevalence of obesity in this study is higher than the findings of other national and local studies in Iran, especially in women (almost twice as high) [29]. Although the observed difference in obesity between residents of various Yazd municipalities is not remarkable, these differences were reported by other studies too [30, 31]. Considering the relationship between obesity and dietary pattern and physical inactivity, and the difference between these two behaviors among residents of Yazd municipalities, as seen in this study, this difference in obesity prevalence between areas was expected.

Physical activity is not enough in half of the adult population of Yazd with a 20% difference across Yazd municipalities (e.g. 42.6% in municipality 1 vs. 64.4% in municipality 2). Inadequate physical activity in some areas is remarkably lower than the country average [32]. Physical inactivity in Yazd is more common than Kerman and the national average, although the findings of a previous study in Tehran and Yazd show a lower level. These differences may be due to different measurement tools. The apparent relationship between lower physical activity in women and lower SES aligns with results similar to other, similar studies [28, 33, 34]. Cultural constraints and the lack of adequate indoor and outdoor sports facilities space can also affect people’s physical activity. The lack of attention to the green-sports spaces and the service distance in Yazd urban development projects has caused limited access in some municipalities, especially 1–2 and the marginal area [35]. Also, more expensive spending in the private sector can limit to access for deprived areas. Inequality in the availability of public or private sporting equipment and the distance to sporting venues may affect this difference [36].

The study shows that 18.5% of adults engage in tobacco use (cigarette or water-pipe), which is lower than the reported national prevalence rates. Similar to other studies conducted in Iran, men smoke more than women, although the gap is smaller for water-pipe usage [37]. An investigation of female tobacco consumption has also shown an alarming upward trend in recent years, in Yazd [38]. Significant differences in the prevalence of smoking in urban areas may show the role of social determinants on smoking, which has also been reported in other studies [38]. The geographic distribution of tobacconists, especially hookahs, in different parts of the city and the association of easy access to tobacco use can help in identifying the factors that influence usage.

Physical inactivity, unhealthy diet, and obesity in urban areas are the most important risk factors of T2DM, which is a major CVD risk factor itself [39]. The differences in the prevalence of T2DM among regions may be reflective of socioeconomic level, and the lifestyle and dietary behavior associated with it, as explained above [40]. The results of our study indicated differences in geoghrafical patterns of T2DM, as reported in other studies [41]. A further study of the contribution of each dimension of socioeconomic level and their differences across regions is necessary to allow effective preventive interventions for these non-communicable diseases. The higher prevalence of T2DM in Yazd compared to other provinces, as well as its increasing trend compared to previous years [28], requires a further ethnic and geographical investigation of the prevalence of T2DM and its risk factors.

The prevalence of hypertension in Yazd is also higher than the country average and is occurring at a higher rate compared with previous years [28]. Obesity, tobacco smoking, sedentary lifestyle, unhealthy diet, and economic status are known risk factors for high blood pressure. Although this study investigated the differences in prevalence, of these risk factors across urban areas, unlike other studies [42, 43], the prevalence of high blood pressure across Yazd municipalities was not statistically significant. Given the history and physical examination of the participants, the high prevalence of hypertension in all areas of Yazd is alarming.

This study, for the first time, addresses the differences in the risk factors of NCDs diseases in different regions of Yazd. Multi-stage random sampling using a standard protocol from all neighborhoods in Yazd, with 95% of respondents participating, is one of the strengths of this study. A high sample size with sufficient power provides an estimate of regional prevalence. Although this descriptive study cannot determine the cause of the most common risk factors for cardiovascular disease in a region compared to other areas. Alcohol consumption is a known risk; however this study has not investigated it.