====== Sections ======

[[Start|Lifelines]] variables are organized per theme in 13 main sections and ~230 subsections.\\
The 13 sections are:

  - [[Children & adolescents]]
  - [[Demographics]] 
  - [[Diseases & Symptoms]] 
  - [[Elderly]] (variables that were specifically collected in participants aged 65+ years old)
  - [[Family health]] 
  - [[Lifestyle & environment]] 
  - [[Medical treatment]]
  - [[Mental health]]
  - [[Nutrition]]
  - [[Physical state]]
  - [[Reproduction & development]]
  - [[Wellbeing & subjective health]]
  - [[Secondary & linked variables]]
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===== Primary and alternative (sub)sections =====

Note that some subsections could fall under more than one section (i.e., "alcohol use" could be seen as a subsection of "lifestyle" or of "nutrition", and "mental illness" could fall under "diseases & symptoms" or "mental health"). Similarly, individual variables may fit in more than one subsection. 
Lifelines __always asigns a primary section and subsection to a variable__, but may asign a second, alternative (sub)section to facilitate the findability of the variable in the online data catalogue. 
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===== Default variables =====
Some Lifelines variables are provided by default in every issued dataset. As a result, these variables are not visible in the data-catalogue. An overview of the default variables can be found [[default_variables|here]].
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===== Changes in variable names =====

Note that we may occasionally change a variable name, if there is a valid reason to do so (i.e. the original name is deemed confusing, too informal, unexpected, inconsistent, or incorrect). You may find a full list of changed variable names following this link: [[changed variable names]]. 
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===== Unfixable variables =====
Seldomly, we find variables that contain mistakes or inconsistencies. Most of the time these mistakes or inconsistencies will be corrected, but not always. You may find a full list of unfixable variables following this link: [[unfixable variables]].