Very thorough treatment of the subject.
Despite the graph cited above, most of the article was talking about longer term (days) exposure.
Clearly anyone with impairment of autonomic nervous system function or fluid regulation (diabetes, kidney disease, autonomic neuropathy, dehydration in the short or , d term) is at higher risk.
I must say, that at 71 I seem to sweat more than I have in the past, despite their saying that sweating decreases with age.