1.1 The Menstrual Health Timeline

{Read time: 6 minutes}

Menopause, also known as the climacteric, can be explained easily, in terms of menstrual health and ovarian aging, viewed with a lifetime lens, from start to finish.

[We call this a menstrual health timeline. This phrase reflects the process of ovarian activity from the point of periods starting, to stopping, and the health outcomes thereafter]

The Menstrual Health Timeline

The moment two X-chromosomes unite the Menstrual Health Timeline is forecast.

From the point of menarche when periods start, the average age being 12, to menopause (day) when periods stop, the ovaries and the brain coordinate an infradian rhythm, known as the menstrual cycle, approximately 450 times, on average over 40 years [1].

Along this timeline, there are acknowledged hormone shifts. The exact date and time cannot be predicted and as they merge from one to another, with no clear stop or start, the phrase used to describe it is a continuum (I appreciate this sounds a tad Star Trek, but will come in handy to know).

The hormone shifts along the continuum are given the following titles:

  • Menarche
  • Pre-menopause
  • Perimenopause
  • Menopause (day)
  • Postmenopause

The mean Age of Natural Menopause (ANM), when menstruation has ceased permanently, for 12 consecutive months, and the final menstrual period (FMP) has occurred is significantly influenced by three factors

1. Race & Ethnicity.

There are differences in biological and hormonal changes in women of different races and ethnicities. For example, the age ranges from 46.7 for Indian women (living in India), 47.16 for Pakistani women, Afro-Caribbean women 49.6, and White women 51 [2,3]. Please read the reference article [2] for more detail on the different kinds of menopause experiences and distinctive characteristics of the major UK ethnic minority groups

2. Smoking

An established risk factor associated with an earlier age of menopause.

3. BMI

A higher Body Mass Index is a risk factor associated with a later age of menopause

Other factors that have a subtle influence on the timeline, independently and combined, are:

  • Sociodemographics
  • Diet and lifestyle factors such as alcohol consumption
  • The average length of menstrual cycles
  • Age of menarche
  • Genetics – between 30-85% of DNA, with a closer link to the maternal side [4]

In addition to the female reproductive organs (ovaries, fallopian tubes, uterus, and vagina), menarche is influenced by complex hormonal interactions involving the hypothalamus, pituitary gland, and ovaries. The adrenal glands, thyroid, and pancreas have also been shown to play a role in menarche. Thyroid hormones are necessary for normal menses, and their deficiency or excess can inhibit menarche or lead to abnormalities in existing menstrual patterns. Abnormally elevated insulin or adrenal androgens can affect normal ovarian estrogen production and decrease pituitary production of LH. The hormone leptin also appears to play a role in maintaining normal menstrual cycles [5]

Physiology, Menarche
Amy E. Lacroix; Hurria Gondal; Karlie R. Shumway; Michelle D. Langaker.

What is Ovarian Aging?

The medical framework for the menstrual health timeline is known as Reproductive Aging. This was defined in 2001 and updated in 2011 and is called STRAW+10.

(Stages of Reproductive Aging Workshop)

The term Reproductive Aging refers to the timeline for all females, whether they have reproduced or not. However, it does not reflect whether an individual has chosen not to reproduce or is unable to. As such to avoid confusion as to who we are referring to we prefer to use the term Ovarian Aging. From the point of ovaries becoming active at Menarche, they start to age. We often hear the phrase ‘menopause is a natural part of the aging process’, well so is puberty.

The ovaries have a developmental timeline. The capacity of potential eggs goes from one million at birth to 25,000 at the point of the tipping point of accelerated ovarian aging, around the age of 37, and to 1000 by menopause day.[1]. (Lesson 3 explains the significance of this in terms of menstrual health)

[NB. The timeline continues even with the use of contraception. The ovaries continue to age and eggs that never reached a natural cycle maturity do not get stored up, they fade away as part of a process called atresia. Pregnancy has a small influence on the total number of menstrual cycles predicted, but not significantly in terms of the overall average age of menopause. The ovaries continue to age each and every month whilst pregnant, and hence it is not on the significant impact list at the top of this lesson.]

The Continuum in more detail

The timeline becomes more contextual if we add some background understanding of where the timeline started, the hormones involved, and how physical & emotional changes occur along the way, from menstruation to menopause, and beyond.

The stages along the continuum are:

  • Menarche – a few years after puberty when ovaries become active, periods start, Initially the menstrual cycle is irregular but then a pattern emerges.
  • Premenopause – the time between the first menstrual period and the onset of perimenopause. The menstrual cycle is often in an established pattern during this phase and the words used to describe this is that periods are regular. Also known as being able to predict fertility, which whilst it is biologically accurate prevents menstruators from looking outside the menstrual cycle in terms of overall health, rather than just reproduction.
  • Perimenopause – a change in ovarian activity occurs, and then the period pattern changes and is referred to as irregular. Some are heavy, some light, some closer together, some far apart until eventually the menstrual cycle stops. It must be noted that irregular does not necessarily mean in frequency. The irregularity can be very subtle and may be in the nature of the bleed time and flow. The assumption is that it will be the frequency that changes, and as such if periods are still appearing to be regular to the individual they do not always spot the early indicators of perimenopause.
  • Menopause (day) – also known as the climacteric, is a retrospective date, when 12 consecutive months have passed with no period.
  • Postmenopause – the day after menopause day until death.

To ensure menstrual health, women, girls, and others who experience a menstrual cycle must have access to accurate biological and practical information. Biological information about the menstrual cycle and its relationship to reproduction and fertility enables understanding of the body for menstrual health and Sexual Reproductive Health and Rights.[6]

Menstrual health: a definition for policy, practice, and research

In summary

Periods start. Periods stop. The timeline is linked to ovarian aging.

Periods have always happened and will continue to do so. Therefore learning about health markers related to menstruation is an effective strategy to support overall health.