Tehran Lipid and Glucose Study

The Tehran Lipid and Glucose Study (TLGS) as the first Community –based large scale long term cohort study in I.R.Iran was designed in 1998. TLGS was initiated in 1999 to investigate non-communicable disease (NCD) and its associated risk factors or determinants among a representative family-based population of Tehran, the capital of Iran.

Methodology

study desing

 The Tehran Lipid and Glucose Study encompasses two major components: Phase I was a cross-sectional study of NCD and its associated risk factors, conducted between February 1999 and August 2001. Phase II is a prospective study begun in September 2001. The reference population in this study consists of individuals, aged 3 years and over, living in District 13 of Tehran.

Study population

Nearly 27,500 people (7,146 households) aged ≥3 years living in District 13 under coverage by three health centers, the Leylatolghadr (7,858), Mohammadian (8,932), and Salavati (10,761) centers, where their health records are available.

Sample size determination

  Sample size was determined to be 14,280 considering the following items:

1. Confidence interval of 95%,
2. Study power of 80%,
3. Predicted prevalence rates of 30% for dyslipidemia in people under 30 years old, and 45% for those 30 years old and over,
4. Attrition rate estimation of 20%,
5. Design effect of 1.25,
6. Seven age groups and two genders.

Sample Selection

  Using cluster random sampling, samples were selected as follows:

1. A list of all households under coverage by the three health centers was prepared.
2. Households were specified according to each health center.
3. Proportions of households under coverage by each health center to the total number of households in the three health centers were determined.

 Lists of all households selected were prepared and their addresses were determined.

Data collection site

In order to collect data from the sample population, The TLGS unit Study Unit (LGSU) was set up in a four-story building, located in an area within easy access of the sample population.

Data collection

• Invitation

All individuals were invited for interviews and medical examinations to the LGSU. Social workers first familiarized them at home with the study objectives and invited them to participate in the study at the second visit; they were asked to sign a written consent and bring it to LGSU following the first visit. At LGSU they underwent:

1. Interview

Each interview was conducted by means of a structured questionnaire to collect demographic data such as personal, educational, occupational, medical and residential details.

2. Medical examination

In this stage, trained physicians collected data on the medical history, blood pressure, peripheral pulse, and thyroid exam. Trained technicians obtained anthropometrical data such as height, weight, hip and waist sizes. ECG was taken from those aged 30 years and over.

3. Blood sampling

Blood samples were drawn after 10-12 hours fasting and the glucose tolerance test (2hPG) was performed in those aged 20 years and over.

• Laboratory procedures

After admission and documentation of personal characteristics and determination of a computer code, a 10-ml sample of venous blood was collected. The samples were kept for one and half hours in normal conditions of the lab. The samples were then centrifuged to separate the sera; all the tests were done daily and some samples (four micro-tubes) were stored in –70C temperature for future studies.

Lifestyle modifications to prevent risks factors

Lifestyle modifications to prevent risks factors and outcomes of non-communicable diseases

The Tehran Lipid and Glucose Study is an ongoing comprehensive health study being conducted by the Research Institute for Endocrine Science (RIES) since 1998 in the Eastern district of Metropolitan Tehran. Currently, the project is in its sevsnth phase. During the first phase of the study (baseline data collection (1999-2001), 15005 subjects, aged 3 years and older, were recruited and analyzed for NCD risk factors, a process which is repeated every three years, in accordance with the standardized protocol.

During the past decades, due to the expansion of urban life, the promotion of public health, the considerable control of infectious diseases, and finally, the increase in longevity, Iran is faced with the alarmingly increasing trend in non-communicable diseases(NCDs), e.g. cardiovascular diseases, diabetes, cancers, etc. The high prevalence of risk factors , such as high blood sugar and lipids, high blood pressure, smoking and obesity are all related to the urban industrial lifestyle and unsuitable habits in the society at large.  The preliminary results of the TLGS study show a high prevalence of risk factors, e.g. high blood pressure (24 %), overweight and obesity (63%), blood lipid disorders (54%), diabetes (11%), and smoking (14%) among the residents of Tehran. Over 60% of hospital admissions and mortalities are attributable to NCDs.  In light of these results, in the second phase of the project, a subgroup study was designed aiming at   lifestyle modification to decrease NCD risk factors and outcomes; by:

• Improving nutritional habits and behaviors
• Increasing levels of appropriate physical activity
• Reducing smoking

The above protocols were implemented at several levels of the society ranging from families, to schools, businesses and public places, such as mosques and other places for holding religious ceremonies and mourning. Using various measures and approaches to achieve their prioritized goals, the protocols aim at implementing comprehensive interventions to promote public health. Empowering different social sectors, and utilizing the present capacities of different social classes, institutions, and regional and local organizations are among the important approaches used for lifestyle modification.

With the help of God almighty, the long-term results of this protocol will be utilized to promoting the health of our Islamic society. On the one hand, valuable experiences for training and empowering human and scientific resources will be gained. On the other, conditions conducive to modifying the framework of health services in the country, in particular, to contain and reduce NCDs, will be facilitated. Simultaneously with achieving these public health goals, the publication of the results of such research in reports and scientific articles, both within the country and internationally, will facilitate the enhancement of research and scientific indices in the country, and prepare suitable grounds for much needed collaborations and exchange of experiences with other scientific /academic institutions worldwide.