The Age of Onset of Menopause

The average age of onset of menopause depends on race, family history and a number of other factors different in each woman. Although the normal age of menopause can vary between 45 years to 55 years, the average age of menopause is 51 years. Surgical menopause, of course, can occur at any time the uterus is surgically removed.

All women are born with a finite number of follicles that are determined genetically. Menopause occurs when this stock of follicles are exhausted at the end of the reproductive life.

It is estimated that there are about 7 million primary oocytes or primary follicles in a 24 week old fetus. These decrease to about 2 million at birth. Of these only about 500 follicles are destined to develop into mature Graafian Follicles. The rest are lost through degeneration.

The age of menopause depends to some extent on whether a woman ovulates (releases an ovum) every month. Most woman do not. Certain factors like the number of children a woman has given birth to, the years spent breastfeeding, years of taking birth control pills (the pills stop ovulation) - each of these factors prevent ovulation and help build up the stock of follicles. This delays menopause.

During pregnancy , that is for 9 months, there is no ovulation. Normally, at least 5 -6 follicles develop in each menstrual cycle during the non-pregnant state. So, each pregnancy means that these follicles remain in excess in the ovaries. The woman who has been pregnant more often, will thus have a larger stock of follicles in her ovaries and will thus menstruate for a longer time.

Ovulation is also arrested in some women during the first 5 - 6 months of active breastfeeding. So, pregnancy and breastfeeding are likely to delay the onset of the age of menopause.

Birth control pills contain hormones that can block the process of oocyte maturation. Ovulation is thus prevented every month. This will help in preventing the decrease in the number of oocytes in the ovaries.

One important factor that should be noted is that lack of ovulation does not prevent the aging of oocytes within the ovary. Over time, oocytes will continue to be lost, even when there is no ovulation as in pregnancy, breastfeeding and taking of birth control pills. But this loss is substantially less than the loss that occurs when ovulation is actually taking place.

There are other factors that also affect the age of onset of menopause. Women with the same ethnic background get their menopause at about the same time. For example, Japanese women are known to get their menopause later than women with African ancestors. This is probably because of a similar genetic component.

Stress, obesity, environmental factors, nutritional deficiencies can all affect the age of onset of menopause. It has even been suggested that climactic conditions can affect the average age of onset of menopause. Women of colder climates generally get their menopause at a later age than women of tropical climates. But this is also probably due to a similar genetic composition of the women who stay at the same place(either colder or warmer climate ) together.

The average age of onset of menopause thus depends not only on the genetic makeup of the woman concerned as well as on other factors which influence her life.