It seems that smell is one of the first senses that gets lost as we get older.

OT to this thread, but reduction in sense of smell is one of the best 10-year lead signals of Alzheimer.

Tails

(Learned that tidbit from the Baltimore Longitudinal Study on Aging (BLSA), run by Johns Hopkins, the western hemisphere's longest running aging study. It's not how good you can smell, it's just about your own chronological loss of that sense. If it all of a sudden takes a large reduction, that's the signal that you might be at risk for getting Alzheimer's in the next 10 years.

One other good 10-year lead warning for possible Alzheimer's is how well you can maintain a consistent gait. The test:

In a wide hallway (such as are in hospitals), place two small cones 10m apart, with a "starting line" taped to the floor abeam one of the cones.
The instructions are: "When I say begin, walk down to, and around, the other cone and return. Walk like you are in a business suit, but are late for an important meeting."
The researcher times you with a stop watch. This is done 3 times to establish an average.
The actual test involves doing 10 laps, without pauses, and each of the laps are timed. Same instructions on how fast to walk.

You might end up with a data set like (time in seconds): 22.1, 22.0, 22.3, 22.1, 22.3, 22.2, 22.4, 22.1, 22.2, 22.0. Relatively consistent. It's when those times start diverging that the 10-year increased chance of Alzheimer's warning flag goes up.)

BLSA is a 2.5 day series of tests, and it's quadrennial from ages 20-60, biannual from ages 61-80, and then annually from age 81 on. It's a full battery of physiological and cognitive tests. Highly recommended, if you can get get accepted into the study. As you might expect, the study is in Baltimore MD.