The age distribution, , in Bretzwil is; 67 children or 8.5% of the population are between 0 and 6 years old and 141 teenagers or 17.9% are between 7 and 19. Of the adult population, 81 people or 10.3% of the population are between 20 and 29 years old. 83 people or 10.6% are between 30 and 39, 144 people or 18.3% are between 40 and 49, and 139 people or 17.7% are between 50 and 64. The senior population distribution is 95 people or 12.1% of the population are between 65 and 79 years old and there are 36 people or 4.6% who are over 80.