It could be so...but the eastern Empire was woven of the same cloth, had the same lead and lasted for another 1,000 years.
It wasn’t so much lethargy, imho, it was complacency and a cultural softness. It was a citizenry that was fed but did not have to work. If they weren’t fed they would have burned the city down. The army became mercenary, not citizen. It shifted far beyond the urban centers where barbarians were paid to be nice, as it were...that was weakness manifest.
Eventually it simply became too much to manage...but to the point of the article: at the height of the peak lead spike was the best times of the empire.
I would say the same thing about us: during several lifetimes of lead paint and lead in other places, we managed to create unsurpassed inventions and a lifestyle unheard of in the world. Trains, boats planes and automobiles, went to the moon, cured infections...all while supposedly swimming in a hazardous lead environment.
Oh yes I hear and understand your reasoning. I have to include the lead effects as well. Just as Benjamin Franklin wrote to a friend about the ill effects in type-setters and the ink due to lead. Not everyone was poisoned and add to that, everyone has different metabolisms meaning huge differences of effects from exposures. One of the things we do know is that in small children there is a loss of IQ between 1 and 7 points for every microgram per deciliter of lead in their blood. That is just one of the insidious ways lead helped in the destruction of a mighty Empire. I also take the need of the Empire to appease the citizenry as a way to quell the aggressiveness in part due to some having had lead poisoning, which in turn could have spurred on others. Yes I know this is speculation, just saying... Again I am not saying lead poisoning was the major cause for the fall, just maybe it was one of the nails in the coffin.