The expression “biological clock” can refer to two different concepts. The biological clock can in fact be understood as a system for measuring biological ageDifferent from chronological age. It is a measure of the body's ageing, based on the effectiveness of the mechanisms that keep cells young and on markers of the functionality of organs and apparatus., which depends on the aging process and can differ even significantly from chronological age. But the same expression “biological clock” can also refer to the mechanisms that regulate circadian rhythms, the sleep-wake cycle, the maturation of the sexual organs and therefore fertility. Let us look at both in a little more detail.
Measuring biological age: Horvath’s biological clock
Steve Horvath, biogerontologist and biostatistician, one of the pioneers in research on biological age, uses the expression “biological clock” to indicate a tool capable of measuring biological age. Indeed, the one that bears his name is one of the best-known biological clocks. It is, to be precise, an epigenetic biological clock, based on the methylation status of DNA (that is, the addition to the DNA molecule of specific chemical groups, called methyl groups). According to Horvath, a biological clock must meet some fundamental criteria to be considered functional: for example, it must apply to most cell types (and therefore to different organs and tissues) and, above all, it must be able to predict the risk of falling ill and, in general, the decline in health status. In fact, the idea behind the concept of the biological clock understood as a tool for measuring biological age is to make it possible to monitor the state of health and aging of people (and of their organs) regardless of chronological age.
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The internal biological clock
What, on the other hand, is the internal biological clock? As anticipated, it is a system through which our body adapts, for example, to the alternation of day and night, or which allows some animals to adapt their metabolism to the season (think, for example, of animals that hibernate in winter).
How does the internal biological clock work?
But how does the internal biological clock work? Which “organ” regulates it? As explained in a section of the website of the National Institutes of Health (NIH), the main agency dealing with public health research in the United States, in humans the biological clock is controlled by a brain structure called the suprachiasmatic nucleus, located in the hypothalamus. One of the functions of this region of the brain is in fact to regulate the release of melatonin, a hormone involved in the sleep-wake cycle. Melatonin production increases in the evening, while during the day, when our eyes perceive sunlight, melatonin production decreases. In addition, the NIH experts further explain, the suprachiasmatic nucleus synchronizes circadian rhythms in the different organs and tissues of the body.
What is the circadian cycle?
The circadian cycle or rhythm is simply one of the consequences of the proper functioning of the biological clock. It consists, in fact, of the physical and mental changes our body undergoes over 24 hours. The circadian cycle is linked to many important functions of our body, such as digestion and metabolism, hormone release, body temperature control and the immune response.
What happens if the circadian rhythm is altered?
The circadian cycle can be altered by several factors. Quite simply, traveling to a country in a different time zone can cause temporary problems of insomnia or, in general, alteration of the sleep-wake cycle. There are also genetic variants, the NIH experts point out, that can influence the proper functioning of the biological clock, and the same can apply to some neurodegenerative diseases. The blue light emitted by electronic devices can also affect the circadian rhythm, especially if we use smartphones, tablets, PCs or other devices for a long time before going to sleep. Alteration of the sleep-wake cycle and of the circadian cycle in general, if prolonged over time, can be a risk factor for the development of diabetes, obesity, mood disorders and high blood pressure.
Is it possible to “reset” the internal biological clock?
Since it is influenced by many different factors, there is no universally valid solution to “reset” one’s internal biological clock in the event of alterations, for example, of the circadian rhythm. It depends on whether the causes are genetic, pathological or perhaps linked to bad habits. In general, from a prevention perspective, one aspect to consider may be precisely the use of electronic devices before going to sleep, which should be limited.
