What Ludwig described
In 1977 Erich Ludwig argued that hereditary thinning in women was far more common than generally believed, and that it was missed because it does not follow the male pattern. Instead of receding temples, it thins the top of the head behind a band of hair that stays at the front. In his grades, the thinning area starts one to three centimetres behind the frontal hairline and becomes more pronounced from grade to grade. Ludwig noted that a male-type pattern also occurs in women, but rarely, and suggested grading those cases on Hamilton's scale for men.
Based on: Ludwig 1977; Gupta & Mysore 2016
The Christmas-tree pattern
In 1999 Olsen, a dermatologist at Duke University, pointed out that the part line is where this pattern shows best, and that thinning is often heaviest just behind the front hairline and fades towards the crown. Seen from above, the widened part looks like a Christmas tree with its broad base at the forehead. Ludwig's grades did not include this frontal accent, so a part that widens most towards the forehead can look milder on his scale than it is. That is why a part photo is worth reading along its whole length, and why the GlowUp Face part check reports widening towards the front as a separate measure.
Based on: Olsen 1999
The Sinclair scale and other ways to grade
Several scales grade the same pattern in finer steps. The Sinclair scale, introduced in a 2004 study, uses five pictures of a centre part, from 1 (a normal part) to 5 (advanced thinning), and the closest picture gives the grade. In that study, 97 percent of women graded 3 to 5 were confirmed on biopsy to have female-pattern hair loss, while the mild grades were far less clear-cut: among women graded 1 or 2, about six in ten had pattern hair loss and most of the rest had chronic shedding, a different condition. The Savin scale and the BASP classification grade density on top in other ways, and BASP covers men and women alike.
Based on: Sinclair et al. 2004; Gupta & Mysore 2016; Lee et al. 2007
When it starts and how it moves
The American Academy of Dermatology describes female-pattern hair loss as the most common cause of hair loss in women. For most it begins in midlife, in the 40s, 50s or 60s, although it can start earlier. It tends to progress slowly: the part widens, hair near the temples may recede a little and, without treatment, some women go on to develop widespread thinning. Women rarely lose all their hair the way some men do. It is more common after menopause, which suggests that hormones play a part alongside the genes a person inherits.
Based on: American Academy of Dermatology
What a photo can and cannot tell you
A wider part is not always female-pattern hair loss. Shedding after an illness, childbirth or a stressful period, iron deficiency, hormonal conditions such as polycystic ovary syndrome, tight hairstyles and some medicines can look similar, and more than one can be at work. A photo shows how much scalp is visible, not why. If the thinning is new or fast, if hair comes out in clumps, or if the scalp itches, burns or flakes, see a doctor or dermatologist, who can examine the scalp closely and arrange tests if needed. Hair loss with a medical cause often settles once that cause is treated, which is one more reason to have it checked early.
Based on: American Academy of Dermatology; NHS