Reacción a "Continued use of melatonin for insomnia is associated with an increased risk of heart failure"

It is a case study (melatonin intake) versus control (no intake) with a large number of subjects studied over a long period of time, taking numerous variables into account. It is well designed according to the data in the summary of the study. The conclusions in these studies are that a relevant finding is linked to another with statistical significance. This does not imply that the finding is necessarily caused by the other (taking melatonin for at least a year); simply that they coincide, but they raise alarm bells. As the authors rightly say, it would be advisable to conduct more well-designed clinical trial-type studies to try to confirm a closer causal relationship, but I find it very relevant. We will have to wait until the full study is available to see the possible relationship with melatonin doses taken. If this has been taken into account, it could be an important piece of information.

Context: the discussion about the timing and dosage of melatonin is a hot topic among specialists worldwide, with advocates of long-term and/or high-dose use and detractors who advise caution in both cases due to the lack of reliable data on the subject.

Melatonin is a neurohormone that is responsible for the onset of the sleep window that promotes the onset of night-time sleep. It is secreted between one and three hours before the onset of this window under normal conditions, with the right environmental circumstances, by stimulating its brain receptors. However, it is also known that melatonin receptors are present in many other organs of the body, including the heart. The effects of stimulating these receptors have been linked to numerous functions, such as antioxidant and immune effects and the probable regulation of the functioning of these organs at the level of the circadian biological rhythm. It has not been proven that high doses of melatonin are more helpful in inducing night-time sleepiness, and the possible long-term effects on the brain are not well understood, including the possible saturation-inhibition of brain melatonin receptors. It is therefore recommended that it be taken continuously for a short period of time, i.e. a few months.

The high or very high doses recommended by its advocates, and/or long-term use, are mainly linked to its possible beneficial effects on other organs at the antioxidant and immune levels, including in cancerous diseases, with promising but still insufficient evidence, especially in terms of tolerance and possible harmful effects. The alleged safety of melatonin in the long term and/or at high doses is still not entirely confirmed at present. This work could change many things in these perceptions, if it is confirmed and replicated in other clinical trial-type studies. As an initial finding in many subjects and in the long term, it is very relevant and will have a profound impact.