The age distribution, , in Trélex is; 203 children or 15.1% of the population are between 0 and 9 years old and 228 teenagers or 17.0% are between 10 and 19. Of the adult population, 74 people or 5.5% of the population are between 20 and 29 years old. 160 people or 11.9% are between 30 and 39, 295 people or 21.9% are between 40 and 49, and 154 people or 11.5% are between 50 and 59. The senior population distribution is 139 people or 10.3% of the population are between 60 and 69 years old, 67 people or 5.0% are between 70 and 79, there are 23 people or 1.7% who are between 80 and 89, and there is 1 person who is 90 and older.