The current study is based on the data obtained from the final evaluation of IHHP in 2007. Details of IHHP, including sample size, data entry and data analysis were published previously.12
Sampling was performed using multistage and random cluster method. The study population in the districts of Isfahan, Najaf Abad, and Arak were classified into urban and rural based on 2006 public census.
Nearly 5–10% of the population was enrolled in the study. Individuals’ aged ≥ 19 years were randomly selected from each house. The calculated sample size was 9572 people. Sample size in this study was calculated according to age, sex and place of residence. These three districts have less varied population with fewer immigrants compared to Iran's capital and other cities. The participants had to have lived in these regions for at least 10 years. The exclusion criteria were pregnancy, mental retardation. Informed written consent was obtained from all participants after they were briefed about the study. Other information was obtained in house visits by trained personnel. The next day, blood samples were taken from these individuals after 12 hours of fasting to measure triglyceride (TG), total cholesterol (TC), LDL-C and HDL-C. TC and HDL-C measurements were conducted via using a Toshiba auto analyzer. LDL-C was calculated with Friedewald's formula.13
HDL-C was measured using the calorimetric enzymatic method.
Demographic factors included age (19–24, 25–34, 35–44, 45–54, >50 years), sex (male, female), marital status (married, single) education (0-5, 6-12, >12 years) and residence area (urban, rural).
TC ≥240 mg/dl and/or receiving cholesterol-lowering medications were considered hypercholesterolemia. Fasting TG ≥200 mg and/or receiving TG-lowering medications were considered hypertriglyceridemia. LDL-C ≥160 mg/dl, HDL-C ≤40 mg/dl in men and HDL-C ≤ 50 mg/dl in women were considered abnormal levels.14
To evaluate stress, the General Health Questionnaire 12 (GHQ12) self-administered questionnaire for general health assessment, was used. This questionnaire consists of twelve 4-choice questions. To determine each individual's stress score based on the GHQ scoring system, choices (a) or (b) were given a score of 0 and for choices (c) and (d) a score of 1 was considered. A total score ≥4 was considered high GHQ (i.e. high stress).16
This questionnaire has been designed for individuals aged 12 years and higher and its validity/reliability has been studied and previously reported in Iran.17
Data were analyzed using SPSS 15. P<0.05 was considered statistically significant. Age groups, sex, residence area, education and lipid profile disorders were expressed in percentages and analyzed using chi-square test. Logistic regression model was used to assess the correlation between stress level and lipid profile. Independent variables, include hypercholesterolemia, hypertriglyceridemia, increased LDL-C, and decreased HDL-C. Age groups,sex and stress levels were considered dependent variables.