Nitpick that doesn't invalidate your question: though the equator line does cross through Brazil, most of the population doesn't live anywhere close to the equator.
Also, Brazil is 4000 kilometers long from north to south.
"Close" is relative. Most of the population of Brazil lives within the tropics, and the furthest point from the equator in Brazil is closer than the southernmost points in the US or Europe, where much of the relevant studies were conducted.