As we age, the brain undergoes functional decline, a process known as “brain aging.” Recent studies suggest that brain aging is not only a consequence of aging itself, but may also play a determining role in lifespan. We aim to deepen our understanding of brain aging at the molecular to tissue levels and to elucidate the role of the brain in regulating aging and lifespan in mammals. In addition, we actively collaborate with experts from diverse fields—such as epidemiology, clinical research, and mathematical modeling—both in Japan and internationally, to develop new approaches for extending healthy human lifespan. Through these efforts, we hope to contribute to a rapidly aging society by enabling people to live longer, healthier lives.