Purity: Age Limits for Menstruation (Ḥayḍ)
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 433:
The bleeding that women above the age of sixty experience is not ruled to be ḥayḍ; however, a woman can experience ḥayḍ between the age of fifty and sixty, although the recommended precaution is that women who are not Qurayshi (sayyidah)[1] and who experience bleeding which would previously have been ruled to be ḥayḍ [i.e. had they experienced it before the age of fifty, it would have been ruled to be ḥayḍ], should refrain from doing the things that are unlawful for a ḥāʾiḍ to do and perform the duties of a mustaḥāḍah.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)
1
A sayyidah is a female descendant of Hāshim, the great grandfather of Prophet Muḥammad (Ṣ).