Obesity -related diseases

Aim and study population

The Netherlands Epidemiology of Obesity (NEO) study is an ongoing population-based prospective cohort study. Between 2008 and 2012, 6,671 individuals aged 45–65 years at baseline have been included.

Aim

Obesity is a well-established risk factor for many chronic diseases. The NEO study is designed to investigate pathways that lead to disease in obesity. The main clinical endpoints of the NEO study are:

• Type 2 diabetes
• Cardiovascular diseases
• Venous thrombosis
• Chronic kidney disease
• Asthma
• Chronic obstructive pulmonary disease (COPD)
• Osteoarthritis
• Cirrhosis
• Depression
• Mortality

Study population and recruitment

Between September 2008 and October 2012, 6,671 men and women living in the greater area of Leiden participated in the NEO study.

Men and women were eligible to participate in the NEO study when they were 45 to 65 years of age and had a self-reported BMI of 27 kg/m2 or higher.

In addition, all inhabitants aged 45 to 65 years from the municipality of Leiderdorp were invited irrespective of their BMI, to allow for a reference distribution of BMI.

Participants were recruited via three recruitment strategies:

1. Via general practitioners in the area of Leiden
2. Through advertisements in local newspapers and through posters distributed in public areas
3. Via the registers of three municipalities surrounding Leiden (Katwijk, Leiderdorp and Teylingen)

Baseline measurements

The baseline data collection of the NEO study took place between September 2008 and October 2012. In total, 6,671 men and women participated in the NEO study. Participants completed questionnaires at home and visited the NEO study center for an extensive physical examination.

Participants were invited to visit the NEO study center at the LUMC after an overnight fast. Prior to the study visit, participants collected their urine over 24 hours and completed questionnaires at home. The participants were asked to bring all medication they were using in the month preceding the study visit to the NEO study site. This included prescription medication, as well as over-the-counter drugs such as painkillers.

At the NEO study center several measurements have been performed, including an extensive physical examination and blood sampling. In addition, in random subsets of participants we assessed abdominal fat, aortic pulse wave velocity, cardiac function, knee osteoarthritis and brain structure by magnetic resonance imaging (MRI), in addition to hepatic triglyceride content measurements by 1H-magnetic resonance spectroscopy (MRS), indirect calorimetry, dual-energy X-ray absorptiometry (DXA-scan), actigraphy, accelerometry, heart rate variability measurements, and sidestream darkfield (SDF) imaging of the glycocalyx. 

Download the list of all baseline measurements (pdf).

Baseline questionnaires

Prior to the study visit, participants completed several questionnaires.

The NEO baseline study questionnaires:

• General questionnaire (demography, health and medical history)
• Food frequency questionnaire [FFQ] (dietary intake)
• Brief Illness Perception Questionnaire [IPQ] for overweight
• Short Questionnaire to Assess Health-enhancing physical activity [SQUASH]
• Knee injury and Osteoarthritis Outcome Score [KOOS]
• Australian/Canadian Osteoarthritis Hand Index [AUSCAN]
• Epworth Sleepiness Scale [ESS]
• Pittsburgh Sleep Quality Index [PSQI]
• Berlin questionnaire (sleep)
• Inventory of Depressive Symptoms [IDS]
• Beck Anxiety Inventory [BAI]
• Brugha questionnaire of negative life events
• Short Form 36 [SF-36] (quality of life)

Follow-up questionnaire

Between 2012 and 2014, NEO participants completed a short follow-up questionnaire.

Between 2012 and 2014, 5228 NEO participants completed a short follow-up questionnaire. This questionnaire assessed the following topics:

• Self-reported weight
• Self-measured waist circumference
• Medical history of sleep apnea
• Short Form 36 (SF-36) quality of life questionnaire

Collection of clinical endpoints during follow-up

NEO study participants are followed for the incidence of diseases and mortality.

Electronic patient records

The NEO study participants are followed for the collection of clinical endpoints through the electronic patient records of general practitioners.

In the Netherlands, general practitioners keep an electronic patient record of each patient. This electronic patient record covers all medical information concerning the patient, including information on medication prescriptions and reports from laboratories and specialists. Medication prescriptions are coded according to the Anatomical Therapeutic Chemical (ATC) codes. Confirmed diagnoses are coded according to the International Classification of Primary Care (ICPC).

Collection of clinical endpoints via electronic patient records

Incident diagnoses of the clinical endpoints are extracted from the electronic patient records of the NEO participants. Four years after the start of the study, data were extracted for the first time. Data extractions are repeated at regular intervals. Up to now, the following diagnoses have been extracted from electronic patient records:

• diabetes
• fractures
• reflux
• cardiovascular disease
• asthma
• COPD
• Cancer

Prevalent diagnoses to assess medical history at baseline

In addition, electronic patient records are used to retrieve information about the medical history at baseline of the participants. When available, this information is used to either complement or replace the self-reported medical history obtained by questionnaire.

Vital status and causes of death

In the future the NEO study will also be linked to hospital admission databases and the Central Bureau of Statistics Netherlands (CBS) for information on diagnoses of diseases, vital status and causes of death.

Study participants gave informed consent for the collection of information from these sources.

NEO research procedure

Research with NEO data is performed according to the NEO Research procedure.

This research procedure includes several checks, approval and documentation, to safeguard transparent and reproducible research. In order to receive a database for analysis, each research question needs to be submitted for approval by the NEO publication committee in the format of a paper proposal. The paper proposal includes a detailed statistical plan, a list of requested variables, and draft tables. A template for the paper proposal will be sent to you by e-mail, after you have been attributed to one of the NEO Work Packages. The NEO Research procedure is shown in the flow chart below and described in more detail in the document that can be downloaded by clicking this button: Download the NEO Research Procedure (pdf).

Variables and codebook

A codebook of all NEO variables is available.

A codebook with all available variables of the baseline measurements of the NEO study will soon be added to the website. For now you can contact the data manager for more information.

In the codebook each variable is described with its format, labels and values. This information can be used to request the appropriate variables for data analysis.

First, the codebook for the baseline data collection will be placed online. In the near future, data collected with the first follow-up questionnaire or obtained through electronic patient records will be also added to the codebook.

Explanation of the codebook tables

Variable Name: name of the variable as used in the NEO database

Label: description of the variable

Format / Categories: describes the format of the variable (e.g. string, numeric, date). In case of a categorical numeric variable, it is described as “Cat /” + the value labels of the individual categories.

Source: source of the variable, i.e., how the data was collected. For example, ‘GenQ’ = general questionnaire that was completed at home. Also see this page for a complete list of baseline data collection methods.

Organisation and work packages

The NEO study is a collaboration between multiple departments of the LUMC and is coordinated by the department of Clinical Epidemiology.

Researchers from the VU University Medical Center Amsterdam (VUMC) are also involved in the NEO study.

The NEO study is governed by the Executive Board, which also functions as the Publication Committee.

All research with NEO study data is embedded in one of the Work Packages. The Work Packages are based on clinical endpoints: Atherosclerosis, Bone Disease, Brain Pathology, Diabetes, Gastric Reflux Disease, Liver disease, Neuroendocrine Disease, Oncology, Osteoarthritis, Pulmonary Disease, Renal disease, Venous thrombosis, and there is a Work Package General Epidemiology.

In addition, there are six Technical Platforms: Statistics, Laboratory, Imaging, Nutritional Status, Omics, and Follow-up. The members of the Technical Platforms meet on a regular basis to discuss quality control, procedures and future initiatives.

Together, the members of the Work Package Groups, Technical Platforms and Executive Board constitute the NEO Study Group. Open the pdf document below for an overview of all members.

The NEO Study Group - organisation and members (pdf)

Funding

The NEO study is funded by the participating Departments, the Division and the Board of Directors of the LUMC, and by the Leiden University, Research Profile Area ‘Vascular and Regenerative Medicine’. These parties have enabled the design, infrastructure and data collection of the NEO study.

Between 2015 and 2020, the NEO study was part of the ENERGISE consortium; a multidisciplinary Dutch research consortium composed of experts in the field of energy metabolism, metabolic health, cardiology and epidemiology. The ENERGISE consortium was supported by the Netherlands Cardiovascular Research Initiative (CVON): an initiative with

 support of the Dutch Heart Foundation (CVON2014-02 ENERGISE).