White noise can be annoying. Every tried to sleep next to the ocean :P

I'd consider the pollutants more factor in this increase thou.

http://www.platinumenergysystems.ca/blog/heavy-metal-toxicity-a-reversible-dementia

Granted Lead has been removed from the majority of fuels around the world, but how about Aluminum engines and the particles that come out with the exhaust fumes.

Hadn't even thought of the aluminum thing.

I actually sleep great near the ocean, or when it's breezy out. What really does my head in is when I'm trying to pay attention to a conversation and there is a general din in the background. Might as well put a diving helmet on.

I like background noise when I sleep too. I really hope there's no relationship there, but I can see how there could be.

Previous studies have suggested a correlation between sleep deprivation and dementia, but it seems unlikely the noise itself would be a factor as long as it doesn't keep you up. I'd think that steady traffic noise would be easy to adapt to, but maybe living near a 'busy road' would also increase the amount of sudden, jarring sounds (sirens, horns, screeching tires etc) that might disrupt sleep.

They actually make white noise generators to help people sleep. You must just be odd.

Actually... You get a lot of particles from the brakes... and those run off into nearby waterways/water table... etc.

One thing not mentioned in the article - they also looked at rates of Parkinson's and Multiple Sclerosis among the same population, and found no association. Worth mentioning because it helps validate the results to a degree.

Causation and Correlation. Maybe people who are predisposed to dementia just really like roads.

You'll generally find higher population densities - especially of older people- near busy roads. Just sayin'.

Not that you live anywhere near a busy road or anything...

I remember reading that one theory about the decrease in crime in the last 20 years is the removal of lead from gasoline. I would be curious to know how that might play in to this. Is there a difference between people who have only lived near roads since the air has become (relatively) lead free and those who have always lived near roads? Do those who lived near roads when young and then moved somewhere else also have a higher rate?

There is another theory from the book Freakonomics. The author postulates that the legalization of abortion led to the drop in crime seen in the 90s and onward. Essentially children that were never born in to destitution could never turn to a life of crime.

I think that the thing I read said that the rate of violent crime decreased faster than the rate of property crime and used that to distinguish. I imagine both may be two factors among many and looking at one or even both theories is a gross oversimplification.