| Aspect | Perimenopause | Premenopause |
|---|---|---|
| Definition | The 4-10 year transition phase leading up to the final menstrual period. | The entire reproductive span from first period to the start of perimenopause. |
| Core Mechanism | Ovarian follicles decline rapidly, causing fluctuating estrogen and progesterone levels. | Ovaries function normally, producing steady cyclic hormones with regular ovulation. |
| Onset Age | Typically begins between ages 40 and 44, but can start in the late 30s. | Starts at menarche, usually between ages 10 and 15. |
| Menstrual Cycle | Cycle length varies by 7+ days; skipped periods are common and progressive. | Regular cycles typically last 21-35 days with predictable flow. |
| Ovulation | Ovulation becomes erratic; some cycles are anovulatory. | Ovulation occurs monthly, releasing one mature egg per cycle. |
| Estrogen Level | Estrogen fluctuates wildly, with overall levels gradually declining. | Estrogen levels remain stable and peak mid-cycle. |
| Progesterone Level | Progesterone production drops more steeply than estrogen, causing imbalance. | Progesterone rises after ovulation and falls before menses. |
| FSH Level | Follicle-stimulating hormone rises above 25 IU/L, often exceeding 30 IU/L. | FSH stays low, typically under 10 IU/L in the early follicular phase. |
| Hot Flashes | Occur in up to 75% of women, often starting with sleep disruption. | Rarely occur; body temperature regulation remains normal. |
| Sleep Quality | Night sweats and insomnia affect 40-60% of women in this phase. | Sleep patterns remain stable without vasomotor disturbances. |
| Mood Changes | Irritability and depression risk increase due to hormonal volatility. | Mood tracks menstrual cycle phases, with mild premenstrual symptoms only. |
| Fertility | Fertility declines but remains possible; unintended pregnancy risk persists. | Fertility peaks in the 20s and remains high through the 30s. |
| Bone Density | Bone loss accelerates to 1-2% per year as estrogen falls. | Bone mass stays stable, peaking around age 30. |
| Cholesterol Levels | LDL cholesterol often rises; HDL may decrease slightly. | Lipid profiles remain stable with protective HDL levels. |
| Heart Disease Risk | Cardiovascular risk begins to increase, especially after age 45. | Pre-menopausal women have lower heart disease risk than men of same age. |
| Vaginal Health | Vaginal dryness and thinning develop due to lower estrogen. | Vaginal tissue remains thick, elastic, and well-lubricated. |
| Libido | Sexual desire may decrease or fluctuate unpredictably. | Libido remains stable, often peaking around ovulation. |
| Headaches | Migraines may worsen or improve as estrogen patterns shift. | Menstrual migraines occur cyclically, typically before menses. |
| Weight Distribution | Abdominal fat increases; metabolic rate slows noticeably. | Weight distribution stays consistent with overall body type. |
| Diagnosis Method | Diagnosed clinically via symptoms and cycle changes; FSH test is supportive. | No diagnosis needed; confirmed by regular cycles and absence of symptoms. |
| Duration | Lasts 4-10 years, ending at the final menstrual period. | Spans 30-40 years, ending when perimenopause begins. |
| Contraception Need | Required until 12 consecutive months without a period. | Required throughout if pregnancy is not desired. |
| Hormone Therapy | Low-dose birth control or HRT may be used to manage symptoms. | Hormonal contraceptives are used for birth control, not symptom relief. |
| Bleeding Pattern | Heavy, prolonged, or unpredictable bleeding is common. | Bleeding is regular, lasting 3-7 days with normal volume. |
| Breast Tenderness | May increase due to estrogen surges, then diminish over time. | Cyclic breast tenderness occurs in the luteal phase. |
| Skin Changes | Collagen decreases, causing dryness and reduced elasticity. | Skin retains firmness and hydration with normal aging only. |
| Hair Changes | Thinning on scalp and increased facial hair may occur. | Hair growth patterns remain unchanged. |
| Energy Levels | Fatigue is common due to sleep disruption and hormonal shifts. | Energy remains consistent across the cycle. |
| Medical Monitoring | Annual visits recommended; bone density and lipid screening advised. | Routine gynecologic care with Pap smears and breast exams. |
| Best-Fit Scenario | Women aged 40-50 experiencing irregular cycles and vasomotor symptoms. | Women in their teens through late 30s with regular cycles and no menopausal signs. |
Perimenopause is the multi-year transition before menopause, typically starting in the mid-40s. It marks the gradual decline of ovarian function and estrogen production. This phase prepares the body for the permanent end of menstruation, often lasting four to eight years.
Perimenopause is the physiological period characterized by fluctuating gonadotropin and ovarian hormone levels, resulting in irregular menstrual cycles and vasomotor symptoms. This transitional stage begins when cycle length variability exceeds seven days and concludes after twelve consecutive months of amenorrhea, signaling menopause.
| Characteristic | What It Means in Practice |
|---|---|
| Cycle irregularity | Menstrual intervals shift by more than seven days, often producing shorter or longer cycles than your historical pattern. |
| Hot flashes | Sudden warmth spreading across the face and chest, frequently accompanied by sweating and a rapid heartbeat. |
| Sleep disruption | Night sweats or hormonal shifts interrupt deep sleep, leading to daytime fatigue and reduced concentration. |
| Mood fluctuations | Estrogen changes affect serotonin pathways, causing irritability, anxiety, or depressive episodes without external triggers. |
| Vaginal dryness | Declining estrogen thins vaginal tissues, reducing lubrication and potentially causing discomfort during intercourse. |
| Heavy bleeding | Anovulatory cycles produce thicker endometrial lining, leading to heavier or prolonged menstrual flow. |
| Breast tenderness | Hormone surges and drops create swelling or soreness in breast tissue, similar to premenstrual symptoms. |
| Reduced fertility | Egg quality and quantity decline, making natural conception less likely though not impossible during this stage. |
| Urinary urgency | Estrogen loss weakens pelvic floor muscles, increasing frequency or urgency of urination. |
| Joint pain | Lower estrogen levels reduce anti-inflammatory effects, causing stiffness or achiness in knees, hands, or shoulders. |
| Advantages | Limitations |
|---|---|
| Natural fertility decline reduces unplanned pregnancy risk, allowing couples to stop contraception after medical confirmation. | Irregular ovulation still permits conception, so unintended pregnancies occur in women over 45 who discontinue birth control prematurely. |
| Menstrual cycles often become less painful, with some women reporting fewer cramps and lighter premenstrual syndrome symptoms. | Heavy, prolonged bleeding can cause iron-deficiency anemia, requiring supplementation or medical interventions like endometrial ablation. |
| This transition prompts many women to prioritize preventive health screenings, including bone density tests and cardiovascular assessments. | Hot flashes disrupt work productivity and social interactions, with severe cases lasting over seven years in some women. |
| Hormonal changes may reduce estrogen-sensitive conditions like endometriosis symptoms, offering relief from chronic pelvic pain. | Sleep fragmentation from night sweats impairs cognitive function, increasing accident risk and reducing work performance. |
| Perimenopause marks a natural life stage, allowing women to anticipate menopause and plan for long-term health strategies. | Mood disturbances can strain relationships and lead to misdiagnosis of depression, delaying appropriate hormone therapy. |
| Lower estrogen levels reduce breast density, potentially improving mammogram accuracy for cancer detection during this period. | Vaginal atrophy causes painful intercourse, often untreated due to embarrassment, leading to reduced intimacy and relationship conflict. |
| Many women report increased self-awareness and confidence, feeling liberated from menstrual-related constraints. | Joint pain and stiffness may limit physical activity, contributing to weight gain and increased cardiovascular risk. |
| This phase offers an opportunity to reassess lifestyle habits, with many adopting healthier diets and exercise routines. | Urinary urgency and incontinence cause social withdrawal, with many women avoiding exercise or public outings. |
| Hormone therapy during perimenopause effectively manages vasomotor symptoms for most eligible women. | Hormone therapy carries rare but serious risks including blood clots and breast cancer, requiring careful individualized risk assessment. |
| Perimenopause eventually ends, with most women reaching menopause by age 55 and symptom relief thereafter. | The unpredictable duration and symptom severity create prolonged uncertainty, affecting career decisions and quality of life for years. |
Premenopause is the reproductive phase before any menopausal transition begins. It starts at puberty and continues until perimenopause, typically lasting through a woman's 30s or 40s. During premenopause, menstrual cycles remain regular, and hormone levels follow normal monthly patterns, allowing natural fertility.
Premenopause is the entire span of a female's reproductive years from first menstruation until the onset of perimenopause, characterized by regular ovulation, predictable menstrual cycles, and stable estrogen and progesterone production. This phase ends when cycle variability first appears, usually between ages 40 and 44, marking the start of perimenopause.
| Characteristic | What It Means in Practice |
|---|---|
| Regular cycles | Menstrual periods occur every 21 to 35 days with predictable timing and flow. |
| Normal fertility | Ovulation happens each cycle, enabling natural conception without medical assistance. |
| Stable hormones | Estrogen and progesterone levels follow consistent monthly patterns without major fluctuations. |
| No hot flashes | Vasomotor symptoms are absent because thermoregulation remains unaffected by hormonal shifts. |
| No sleep disruption | Night sweats do not occur, so sleep quality remains typical for the individual. |
| Consistent PMS | Premenstrual symptoms, if present, follow a predictable pattern each month. |
| Normal bone density | Estrogen supports bone remodeling, maintaining skeletal strength during this phase. |
| Regular cervical mucus | Fertile-quality mucus appears mid-cycle, indicating ovulation is occurring normally. |
| No cycle skipping | Periods do not skip months; bleeding occurs at expected intervals without gaps. |
| Baseline libido | Sexual desire remains stable, reflecting consistent hormone levels without sharp drops. |
| Advantages | Limitations |
|---|---|
| Natural fertility allows unassisted conception for family planning. | Unplanned pregnancy remains possible without contraception, requiring active birth control decisions. |
| Predictable cycles simplify scheduling of activities, travel, and exercise. | Menstrual pain, heavy bleeding, or PMS can disrupt daily life despite regularity. |
| Stable estrogen protects bone density and reduces fracture risk. | Endometriosis or fibroids may cause severe pain or bleeding during this phase. |
| Absence of hot flashes means no thermoregulation discomfort. | Hormone-sensitive cancers, such as breast cancer, can develop during premenopause. |
| Consistent sleep patterns support cognitive function and mood stability. | Premenstrual dysphoric disorder can cause severe mood swings requiring medical treatment. |
| Regular ovulation indicates healthy ovarian reserve for future fertility. | Age-related egg quality decline still occurs, reducing conception odds after age 35. |
| No menopause-related vaginal dryness improves sexual comfort. | Sexually transmitted infections remain a risk, necessitating barrier protection. |
| Cyclical hormones support skin elasticity and collagen production. | Migraine attacks linked to estrogen withdrawal can be disabling for some women. |
| Normal cervical mucus facilitates sperm transport for conception. | Uterine conditions like polyps may cause irregular bleeding needing surgical evaluation. |
| Predictable hormone levels simplify tracking of health biomarkers. | Contraceptive side effects, such as weight gain or mood changes, may require method switching. |
| Shared Aspect | How Perimenopause and Premenopause Are Alike |
|---|---|
| Natural Life Stage | Both perimenopause and premenopause are natural biological phases in a woman's reproductive timeline, not diseases or disorders. |
| Ovarian Function | Perimenopause and premenopause both involve ovaries that still produce estrogen, though perimenopause shows declining output while premenopause maintains regular levels. |
| Menstrual Cycles | Both phases feature ongoing menstrual cycles; perimenopause has irregular cycles, while premenopause has regular, predictable periods. |
| Fertility Potential | Perimenopause and premenopause both allow natural conception, though fertility is reduced in perimenopause compared to the peak fertility of premenopause. |
| Hormone Presence | Estrogen and progesterone are actively produced in both perimenopause and premenopause, unlike postmenopause where ovarian hormone output ceases. |
| No Menopause Yet | Neither perimenopause nor premenopause has reached the official menopause marker of 12 consecutive months without a period. |
| Reversible Process | Both perimenopause and premenopause are reversible phases; pregnancy can temporarily halt perimenopausal symptoms, and premenopause is fully fertile. |
| Variable Duration | The length of both perimenopause and premenopause varies widely among women, ranging from a few years to over a decade depending on individual biology. |
| Age Range Overlap | Perimenopause typically begins in the 40s, while premenopause spans the reproductive years; women in their late 30s to early 40s can be in either phase. |
| Hormonal Fluctuations | Both perimenopause and premenopause experience natural hormonal fluctuations, though perimenopause has more pronounced swings in estrogen and progesterone levels. |
| Ovulation Occurrence | Ovulation happens in both perimenopause and premenopause, but perimenopause has skipped or anovulatory cycles, while premenopause ovulates consistently each month. |
| No Medical Treatment | Neither perimenopause nor premenopause requires medical treatment as a standard protocol; both are managed only if symptoms or fertility issues arise. |
| Lifestyle Impact | Diet, exercise, stress management, and sleep quality affect hormone balance in both perimenopause and premenopause, influencing cycle regularity and symptom severity. |
| Bone Density | Both perimenopause and premenopause maintain bone density due to active estrogen, though perimenopause may see early bone loss as estrogen declines. |
| Cardiovascular Health | Perimenopause and premenopause both provide natural cardiovascular protection from estrogen, with lower heart disease risk compared to postmenopause. |
| Mood Regulation | Both phases involve estrogen's influence on serotonin and dopamine; perimenopause has more mood swings, while premenopause has stable mood with possible PMS. |
| Sleep Patterns | Sleep quality is generally preserved in both perimenopause and premenopause, though perimenopause may introduce night sweats that disrupt sleep occasionally. |
| Libido Levels | Sexual desire remains present in both perimenopause and premenopause, with perimenopause experiencing variable libido due to hormonal shifts, while premenopause has consistent drive. |
| Vaginal Health | Vaginal tissue stays lubricated and elastic in both perimenopause and premenopause, unlike postmenopause where dryness and thinning occur. |
| Skin Elasticity | Collagen production remains adequate in both perimenopause and premenopause, though perimenopause may see slight reduction in skin firmness as estrogen wanes. |
| Weight Regulation | Metabolism functions normally in both perimenopause and premenopause, though perimenopause may experience mild weight gain around the abdomen compared to premenopause's stable weight. |
| Cholesterol Levels | Both perimenopause and premenopause typically maintain healthy LDL and HDL cholesterol levels due to estrogen's beneficial effects on lipid metabolism. |
| Insulin Sensitivity | Cells respond to insulin effectively in both perimenopause and premenopause, reducing diabetes risk compared to postmenopause where insulin resistance rises. |
| Thyroid Function | Thyroid hormone production remains normal in both perimenopause and premenopause, with no inherent thyroid dysfunction linked to either phase. |
| PMS Symptoms | Both perimenopause and premenopause can experience premenstrual syndrome symptoms like bloating, breast tenderness, and irritability, though perimenopause may have more intense versions. |
| Cycle Length | Menstrual cycles in both perimenopause and premenopause typically last 21 to 35 days, though perimenopause may have shorter or longer cycles intermittently. |
| Flow Volume | Menstrual flow is normal in both perimenopause and premenopause, with perimenopause occasionally having heavier or lighter periods, while premenopause has consistent flow. |
| Contraception Needs | Both perimenopause and premenopause require contraception to prevent pregnancy, as ovulation can still occur in either phase until menopause is confirmed. |
| Tracking Methods | Calendar tracking, basal body temperature, and cervical mucus monitoring work for both perimenopause and premenopause, though perimenopause requires more flexible interpretation. |
| No Menopause Symptoms | Neither perimenopause nor premenopause has the hallmark menopause symptom of complete cessation of periods; both still have menstrual bleeding. |
| Hormone Testing | Blood or saliva hormone tests can measure estrogen and progesterone in both perimenopause and premenopause, though perimenopause results are more variable day-to-day. |
Choose perimenopause when describing the 4–10 years of hormonal fluctuation before your final period. Choose premenopause only for the fertile, symptom-free years before any transition begins. The deciding variable is symptom presence: irregular cycles, hot flashes, or sleep changes mean perimenopause; regular ovulation means premenopause.
Choose perimenopause when you track cycle lengthening (e.g., 35–60 days), vasomotor symptoms (hot flashes, night sweats), mood shifts, or sleep disruption in your 40s or late 30s. Use it for clinical discussions about contraception needs, bone-density screening, or HRT eligibility. It applies until 12 consecutive months without a period.
Choose premenopause when describing regular monthly cycles, no menopausal symptoms, and confirmed fertility—typically ages 20–40. Use it for baseline hormone testing, fertility planning, or preconception counseling. It excludes any perimenopausal signs and ends the moment cycle irregularity or hot flashes first appear.
| Common Myth | The Reality |
|---|---|
| "Premenopause and perimenopause are the exact same medical condition." | Premenopause is the entire reproductive years before menopause; perimenopause is only the 4-to-8-year transition window immediately preceding the final menstrual period. |
| "Perimenopause only starts when you notice hot flashes." | Perimenopause often begins with subtle cycle shortening or sleep disruption, and irregular periods typically appear 2 to 7 years before hot flashes emerge. |
| "You cannot get pregnant during perimenopause because your eggs are old." | Perimenopause still involves ovulation, and natural pregnancy remains possible until 12 consecutive months without a period have passed. |
| "Premenopause means you have no hormonal changes at all." | Premenopause includes gradual, normal fluctuations in estrogen and progesterone, but these changes are far smaller than the dramatic swings seen during perimenopause. |
| "Perimenopause is a disease that requires mandatory medical treatment." | Perimenopause is a natural developmental stage, not an illness; roughly 20% of women manage symptoms without any medical intervention. |
| "Your periods stop abruptly when perimenopause begins." | Perimenopause typically causes progressively longer or shorter cycles over several years, with skipped months occurring before periods cease entirely. |
| "Premenopause ends at age 35 for most women." | Premenopause lasts until perimenopause begins, which for most women occurs between ages 45 and 55, not at 35. |
| "Perimenopause symptoms are identical for every woman." | Perimenopause symptoms vary widely; some women experience only irregular cycles, while others face hot flashes, mood changes, and sleep problems simultaneously. |
| "Hormone therapy during perimenopause is always dangerous." | For healthy women under 60 who start hormone therapy within 10 years of menopause, the benefits often outweigh risks, particularly for symptom relief. |
| "Perimenopause and menopause are interchangeable terms." | Perimenopause is the transition period before the final period; menopause is a single point defined as 12 consecutive months without menstruation. |
| "Your fertility completely ends the day perimenopause begins." | Fertility declines but does not abruptly end at perimenopause onset; spontaneous conception rates drop to roughly 10% per cycle, yet remain possible. |
| "Premenopause causes no physical symptoms whatsoever." | Premenopause can include mild premenstrual syndrome, breast tenderness, and minor cycle changes, but these do not match perimenopause severity. |
| "Perimenopause only affects women over age 50." | Perimenopause commonly begins in the mid-40s, and about 8% of women experience it before age 45, sometimes starting as early as 35. |
| "Blood tests can reliably predict when perimenopause will end." | No single blood test predicts perimenopause duration; follicle-stimulating hormone levels fluctuate daily, making them unreliable for staging the transition. |
| "Perimenopause requires you to stop all exercise immediately." | Regular weight-bearing and aerobic exercise during perimenopause reduces hot flashes, improves bone density, and stabilizes mood rather than worsening symptoms. |
| "Premenopause is a diagnosis given only to older women." | Premenopause applies to every female from puberty until perimenopause begins, so teenagers and women in their 20s and 30s are all in premenopause. |
| "Perimenopause always causes severe, debilitating depression." | Perimenopause increases depression risk by 2 to 3 times, but most women experience only mild mood swings, and severe depression is not universal. |
| "Natural supplements cure all perimenopause symptoms." | No supplement reliably cures perimenopause; black cohosh and soy isoflavones show modest effects for hot flashes, but evidence for other products remains weak. |
| "Perimenopause is the same as premature ovarian failure." | Perimenopause is a normal age-appropriate transition; premature ovarian failure occurs before age 40 and represents a distinct medical condition with different treatment paths. |
| "Your periods become heavier and more painful during premenopause." | Premenopause typically maintains regular, predictable cycles; significant heaviness or pain more likely signals perimenopause, fibroids, or other gynecologic conditions. |
| "Perimenopause ends immediately after your last period." | Perimenopause officially ends 12 months after the final menstrual period, meaning the transition continues for a full year past the last bleed. |
| "Estrogen levels stay constant throughout premenopause." | Premenopause involves normal cyclic estrogen peaks and troughs across each menstrual cycle, but overall levels remain stable rather than progressively declining. |
| "Perimenopause always causes weight gain that cannot be reversed." | Perimenopause-related weight gain averages 1.5 to 2 pounds per year, but strength training and protein intake can prevent or reverse most of this gain. |
| "Only women who have had children experience perimenopause." | Perimenopause occurs regardless of pregnancy history; nulliparous women experience identical hormonal transitions, though they may face different symptom patterns. |
| "Perimenopause is a short phase lasting only a few months." | Perimenopause lasts a median of 4 years, but it can extend up to 8 years for some women, particularly those who begin the transition before age 45. |
| "Premenopause and perimenopause require the same medical screenings." | Perimenopause warrants closer monitoring of cholesterol, blood pressure, and bone density, while premenopause follows standard age-based screening guidelines only. |
| "Perimenopause causes permanent brain damage or memory loss." | Perimenopause may cause temporary verbal memory lapses, but cognitive function typically returns to baseline after the transition completes, with no permanent damage. |
| "You can skip perimenopause entirely if you are healthy." | Every woman who reaches natural menopause passes through perimenopause; only surgical removal of the ovaries bypasses this transition entirely. |
| "Perimenopause symptoms are all in your head or psychosomatic." | Perimenopause symptoms stem from measurable declines in estrogen and progesterone, and these hormonal shifts affect serotonin, body temperature regulation, and bone remodeling. |
| "Premenopause requires birth control until age 50 regardless of cycles." | Premenopause requires contraception until menopause is confirmed, but during perimenopause, doctors may recommend continuing birth control until 12 months after the final period. |
Difference Between Perimenopause and Premenopause is timing: premenopause is the entire reproductive years before menopause, while perimenopause is the final 4–8 years of transition. Choose premenopause for regular cycles; choose perimenopause when cycles become irregular, with hot flashes or sleep disruptions.
## FAQ ### What is the difference between perimenopause and premenopause? Perimenopause is the transitional phase lasting 4 to 8 years before your final menstrual period, while premenopause refers to the entire reproductive years when your cycle is regular and hormones are at normal premenopausal levels. ### Are perimenopause and premenopause the same condition? No, they are not the same condition; perimenopause is the active decline of ovarian function with irregular cycles and symptoms, whereas premenopause is the stable, symptom-free reproductive stage before any menopausal transition begins. ### Which is better to track for family planning, perimenopause or premenopause? Tracking premenopause is better for family planning because ovulation is regular and predictable, while perimenopause involves erratic ovulation and declining fertility that makes conception timing unreliable and often requires assisted reproduction. ### What are the typical costs of hormone testing during perimenopause versus premenopause? Hormone testing during perimenopause typically costs $50 to $200 per panel and may require multiple tests over months, whereas premenopause testing is rarely needed and costs about $30 to $100 only if a specific issue like thyroid dysfunction is suspected. ### Is it safe to use hormonal birth control during perimenopause? Yes, low-dose hormonal birth control is safe during perimenopause for most healthy non-smoking women under 50, as it regulates bleeding, relieves hot flashes, and prevents pregnancy, but you must discuss risks like blood clots with your doctor first. ### Can perimenopause and premenopause treatments be used interchangeably? No, treatments cannot be used interchangeably because perimenopause requires low-dose hormonal contraception or symptom-specific therapies like antidepressants for mood swings, while premenopause generally needs no treatment unless you are managing a separate reproductive condition like endometriosis. ### What is a common beginner mistake when distinguishing perimenopause from premenopause? A common beginner mistake is assuming irregular periods alone signal perimenopause, but you must also consider age (typically 45-55), the pattern of cycle changes, and confirm with follicle-stimulating hormone (FSH) levels above 25 IU/L on day 3 of your cycle. ### Can I switch from premenopause to perimenopause without noticing any symptoms? Yes, you can switch silently, as about 10% of women enter perimenopause with no noticeable symptoms, and the transition is only confirmed retrospectively after 12 consecutive months without a period, so regular gynecological check-ups are essential for detection. ### What is a real-world use case for knowing whether I am in perimenopause or premenopause? A real-world use case is deciding whether to continue routine cervical cancer screenings, because premenopausal women need Pap smears every 3 years, while perimenopausal women may switch to every 5 years with HPV co-testing, and your doctor bases the schedule on your exact menopausal stage. ### How long does perimenopause last compared to the premenopause stage? Perimenopause lasts 4 to 8 years on average, ending with menopause, while premenopause spans your entire reproductive life from puberty (around age 12) to the start of perimenopause, typically lasting 30 to 40 years.