What perimenopause and menopause are
Perimenopause is the transition during which the ovaries gradually reduce oestrogen and progesterone production. It usually starts after age 40 and lasts about 4 years on average; cycles become irregular and symptoms come in waves.
Menopause is the point at which ovulation stops — confirmed after 12 months without a period, at an average age of around 51. It is a life stage, not a disease, but the fall in oestrogen accelerates bone loss and changes cardiovascular risk, which is why a timely assessment has real preventive value.