Menopause is the reduced functioning of the ovaries  due to aging . 
Therefore the age of fertility is permanently over.

 Menopause is confirmed  when a woman has missed her periods
for 12 consecutive months.  The average age of menopause is 51.

The years from puberty, (when periods start), until menopause
are called premenopause.

Natural Menopause

Natural menopause is a natural , permanent ending of menstruation
that is not caused by any medical intervention.

In the Western world, most women experience natural
menopause between the ages of 40 and 58,  with the
average age around 51. Some women reach natural
menopause as early as their 30's and a few as late as
their 60's.

"Although life expectancy has increased during the past
decades, the age at which women reach menopause has
not changed for centuries. .
Today, most North American women spend at least
one-third of their lives after menopause.

 Two factors that can influence the timing of natural
menopause have been identified:smoking and genetics.

Smokers reach menopause
about 2 years earlier than nonsmokers.
 The genetic link is supported by the fact that women
often experience menopause around the same age as
their mothers and sisters.

 Women who have received certain types of
chemotherapy and/or pelvic radiation for cancer may
also be at risk for earlier menopause.

There is also some limited evidence suggesting
that a woman may experience menopause
earlier than average if she has never delivered
a baby, has a history of heart disease, is
medically treated for depression, was exposed
to toxic chemicals, had pelvic surgery, or had
treatment for epilepsy.

 No clear correlations have been found between age at
menopause and race, age at first period, or use of birth
control pills".
( Quoted from the Menopause Guidebook
by The North American Menopause Society.)

Perimenopause

Perimenopause is the transition phase before menopause. 
Sometimes it  lasts 6 years or more, and ends 1 year after the final
menstrual period.

Perimenopausal changes are caused by declining levels of ovarian
hormones.As the levels decline, they do so erratically, sometimes
becoming even higher than normal.

Irregular  menstrual periods, hot flashes, night
sweats, vaginal dryness, sleep disturbances, and mood
swings occur during perimenopause.

It's important to remember that during perimenopause,
a woman may be able to conceive, although fertility is  
very low.

Induced Menopause

Induced menopause is when menstrual periods stop
because of  a medical intervention, either by surgery or
cancer treatments.

Removing the uterus (hysterectomy) does not cause
menopause if the ovaries are left in place, although
menstrual bleeding and fertility end.

 If one or both ovaries remain a hysterectomy usually
brings on the end of ovarian estrogen production an average
of 2 to 3 years earlier than normal.

Women undergoing chemotherapy or radiation in the
pelvic area, or who have had their ovaries removed,
experience the menopause symptoms of hot flashes,
night sweats, and vaginal dryness much more severely
than those experiencing natural menopause. 
This is due to the abrupt  loss of estrogen. 
Also the emotional impact of induced menopause is usually
greater than with natural menopause.

Women who experience induced menopause usually  
have a greater need for treatment to control their
menopause-associated symptoms than women who
undergo natural menopause. 
Because these women are often younger, they need ongoing
monitoring and sometimes treatment to lower the risk of menopause
associated diseases such as osteoporosis later in life.

Premature Menopause

Premature menopause is when a woman reaches menopause ,
either surgically or naturally at or before age 40.
 Women experiencing  natural premature menopause go through
perimenopause and may have the same symptoms as women with
natural menopause, including hot flashes, night sweats, vaginal dryness
and sleep disturbances.
These women spend more years without estrogen, and are at a greater risk
for osteoporosis and heart disease.

Postmenopause

Postmenopause is all the years past menopause.

Hot flashes or "hot flushes" are thought to be the result of
changes in the hypothalamus, the part of the brain that
regulates the body's temperature. If the hypothalamus
senses that a woman is too warm, it starts a chain of
events to cool her down. Blood vessels near the surface
of the skin begin to dilate (enlarge), increasing blood
flow to dissipate body heat. This produces a red, flushed
look to the face and neck, accompanied by instant
perspiration, to cool the body down.

 In some women, an "aura" (an uneasy feeling), occurs
just before the hot flash. An increased pulse rate and a
sensation of rapid heart beating may also occur.

Hot flashes are often followed by a cold chill. Some women
experience only the chill.

Hot flashes that occur at night often interfere with sleep,
and are strong enough to wake a woman up. If a woman
perspires heavily, the condition is called night sweats. 

It's a myth that menopause makes women irritable.
Sleep disturbances cause fatigue and lead to irritability.

Menopause is not the only cause of hot flashes. .. Hot
flashes can also be one of the signs of an infection,
thyroid disorder ,diabetes, tuberculosis, leukemia, or
lyme disease. Additionally, some drug therapies, such as
tamoxifen (Nolvadex) for cancer and raloxifene (Evista)
for osteoporosis, can cause hot flashes.

"  More than two-thirds of North American women have
hot flashes during perimenopause.
Women whose ovaries are removed, inducing surgical
menopause, often have severe hot flashes that begin
immediately after surgery and last longer than those in
women reaching menopause naturally.

Menopause-related hot flashes usually follow a consistent pattern
unique to each woman.

Some hot flashes are easily tolerated, others are annoying or
embarrassing, and still others can be debilitating.

Most women experience hot flashes for 3 to 5 years before they taper off.

Although some women never have a hot flash or have
them only for a few months, others may have them for
many years, even into their 70s or beyond. There is no
way of predicting when they will start-or stop.

Hot flashes often increase with stress and may be
associated with palpitations (rapid heartbeat) and
feelings of anxiety.

The unsettling feeling that precedes a hot flash can mimic
a "panic attack" in some women."

(Quoted from the Menopause Guidebook by
The North American Menopause Society)

Natural Remedies

There are many ways to treat sleep problems caused by menopause.

• Try to identify personal hot flash triggers. These might
  be stress,  a warm room, using a hair dryer, strong
  emotions, hot drinks, hot or spicy foods, alcohol,
  caffeine, and cigarette smoking.
  
• Decrease alcohol and caffeine intake.
• Natural remedies are another option to help treat sleep problems. Chamomile tea, melatonin, and herbs such as valerian root and kava kava are suggested.
  
• Taking calcium 500 mg along with magnesium has a calming effect on the body. Talk to your doctor about a prescription that may help you.

   (Quoted from "Menopause and Its Effect on Your Sleep")