I read in most of the clinical studies that they maintain a level of vitamin D in deficient patients by giving high doses and instantly check its response in a specific disease condition. My point is that any disease related to vitamin D deficiency take a long time to be shown up therefore, to evaluate comprehensive effects of vitamin D supplementation, a long term follow up should be required. Am i right or wrong?

Asked by  Yasir Mahmood on October 13, 2014

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  • Will Hunter
    Keymaster
     Will Hunter on

    Yasir,

    I believe you are correct, at least in regards to certain chronic diseases that develop and progress over longer periods of time.

    There are a couple reasons as to why these clinical studies are not of a longer duration.

    The first reason is cost. Sometimes finances will limit the length of time the study can be conducted for.

    The second reason is participant compliance. Usually, the longer a study is conducted for the greater the attrition rate is. The attrition rate is a measurement of the amount of people who drop out of a study.

    • This reply was modified 2 years, 1 month ago by  Will Hunter.
    Answered by  Will Hunter on

    • Amber Tovey
      Keymaster
       Amber Tovey on

      I agree with Will’s response. A high attrition rate can greatly skew results. In order to fix this, researchers often use the intention to treat analyses, which means they include the participants’ data no matter if they dropped out or not. This is used to avoid misleading results which can arise from non-random attrition.

      For example, if people with a more serious form of a condition are more likely to dropout of the study, and the researchers do not perform an intention to treat analyses, then the results will likely show that an ineffective treatment has positive effects.

      Intention to treat analyses somewhat compensates for attrition rate. Though, if one treatment provides an obvious benefit compared to the placebo, wouldn’t it be inhumane to continue giving placebo for half of the participants while the other half of the participants’ condition is improving? I believe this could be another reason for shorter length studies. Although, like Will said, cost probably limits the duration the most.

      Answered by  Amber Tovey on
Answers

  • DocFlorian
    Participant
     DocFlorian on

    Shortly: you are right. From my own experience with my patients I can say that there are some rhythms we should consider. After 3 months we see the first stabilisation effects – better to look at after 6 months.

    Answered by  DocFlorian on

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