The thinning of hair on the top of the head at the age of 35 may be caused by physiological factors such as heredity, bad habits, etc.; or pathological factors such as seborrheic alopecia and scalp folliculitis. 1.Physiological factors: parents have thinning hair on the top of the head, affected by hereditary factors, their children may appear this situation; often work overtime and stay up all night, lack of sleep, improper diet, and gradually increase in age, which may lead to thinning hair on the top of the head; the usual work pressure, sudden changes, emotional shock, which can lead to a large number of hair loss, hair on the top of the head may become thinner. 2. Pathological factors: Pathological factors, such as seborrheic alopecia, scalp folliculitis, discoid lupus erythematosus, scalp hair lichen planus, congenital oligodactyly, and other diseases, may lead to thinning hair on the top of the head. To summarize, there are more reasons why hair on the top of the head becomes thin at the age of 35. It is recommended to improve bad habits, go to the dermatology department of the hospital if necessary, look for the cause, and combine with the doctor’s advice for treatment.