The average menstrual cyclelasts for 28 days. This cycle begins on the first day a woman starts menstruating and ends on the first day of her next period. For some women, this cycle can, however, be longer and for some, it can be shorter. There are several factors which can influence its lengths, such as sex hormones, the environment, the woman’s psychological state her diet and her health in general.
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However, according to a study carried out by Inserm (The French National Institute of Health and Medical Research) and published in November’s edition of the Environmental Pollution journal, there could be another factor that also influences how smoothly the menstrual cycle runs...air pollution.
Several studies have already demonstrated the toxic health effects of the pollutionthat lingers in the air, particularly fine dust particles. Once inhaled, a fraction of these particles can find their way into the bloodstream, the heart, the brain and the reproductive organs and this can have consequences for the individual involved.
Up until now, little research has been carried out on the impact that pollution has on how the ovaries function during the different phases of the menstrual cycle.
A prolonged follicular phase
At the Fertility Observation Center in France (Obseff) 184 women, who weren’t taking any kind of hormonal contraception, took part in a study. Over the entire duration of one of their menstrual cycles, a sample of their urine was taken daily or every two days. Their hormonal levels were also tested in order to calculate how long each of their different phases lasted: the follicular phase (from the first day of the period to the day ovulation starts), ovulation and finally the luteal phase (from ovulation to the first day of the following period).
Over this period of time and also 30 days before the beginning of their cycle,researchers measured the levels of fine dust particles (PM10) and the levels of nitrogen dioxide around the homes of the women who took part in the study.
By the end, their results showed that the length of the follicular phase was on average 0.7 days longer for every 10µg/m3 of fine dust particles lingering in their environment and the air. As a result, they now believe that this phase, which precedes the ovulation phase, tends to be longer when air pollution is worse, even during just brief exposure.
Alteration to the brain-ovarian axis
Furthermore, researchers suspect that these fine dust particlesalter the way the hypothalamic-pituitary-ovarian axis works. This axis is responsible for transmitting hormone information between the hypothalamus in the brain, the pituitary gland and the ovaries but the results that were recently obtained have not revealed much about the impact the increased duration of the follicular phase could have on female fertility. Further studies will need to be carried out on a larger scale in order toobtain clearer and more concrete results.
According to the World Health Organisation (WHO), this hypothesis is incredibly significant and important, since nine out of ten people in the world breathe polluted air. In 2016, it was estimated that 4.2 million premature deaths were due to factors linked to the health consequences associated with pollution.