The age at which the menopause begins is one which varies owing to
manifold conditions, congenital and acquired, owing to the local
influences which have been brought to bear on the reproductive organs
during the menacme, and to the general circumstances of life during this
period. In Northern Europe it commonly begins some time between the ages
of 40 and 50 years. According to the most trustworthy statistical data,
the commonest age for the onset of the menopause is between the ages of
45 and 50 years. Next to these in frequency we find the menopause
commencing between the ages of 40 and 45 years. If, however, the
menopause does not begin during the fifth decennium, it is more apt to
occur during the quinquennium after 50 than during the quinquennium
preceding 40 years of age; that is to say, an abnormally late menopause
is more often met with than an abnormally early menopause. In a very
small proportion of women does the menopause begin either after the age
of 55 or before the age of 35.