I'm really not sure what you mean by "positive" so I'll venture a guess.
When you get older, certainly there are tissues in the body that deteriorate and that have bee subject to a lot of wear and tear throught the years (muscle and nerve tissues are no exception). What would most be expected to be seen with an EMG:
What COULD POSSIBLY be seen with the nerve conduction study due to the aging process or simply wear and tear of the body: slowed conduction velocity, lowered sensory nerve action potentials, lower compound muscle action potentials . . . the combination of those indicating loss of some myelin and axons.
What COULD POSSIBLY be seen with the EMG due to the aging process or simply wear and tear of the body: an increase in motor unit amplitude size and/or duration, indication reinnervation OR a decrease in motor unit amplitude, indicating loss of muscle OR a combination of both. Active denervation (i.e. positive sharp waves and fibrillations) would probably not be seen unless the EMG was done at just the right time to find them.
There would certainly be variability when it came to all of the above, depending on what muscles and nerves were tested.
I'm not sure if you're asking whether an elderly person would have an EMG that is similar to ALS . . . but if you are . . . the answer is no, unless of course they did have ALS. If El Eschorial criteria are not met, then you will not have an EMG that is indicative of ALS and won't be given that diagnosis.
