In terms of direct death-count relating to the incarceration itself, there are reports of approximately a dozen deaths as a result of shootings (during various escape attempts) as well as several children and elderly people dying as a result of "inadequate health care".
In terms of general longevity, there have been numerous reports into the long-term results of incarceration, the general concensus being that internees had nearly a double incidence of heart disease and stress-related mortality outcomes:
"Survey information found former internees had a 2.1 greater risk of
cardiovascular disease, cardiovascular mortality, and premature death
than did a non-interned counterpart. California Nisei-age individuals,
the proxy for internment, died 1.6 years earlier than Hawaiians who
represented non-interned status. I concluded traumatic stress has
life-long consequences even in the presence of efficacious coping
"The Experience of Injustice: Health Consequences of the Japanese American Internment", Gwendolyn M. Jensen, 1997.
Overall, it's worth stressing that these were not death camps, People were not randomly dying of minor ailments, maltreatment, overwork or starvation. The crude rate of mortality within the camps was approximately 1.5% and essentially the same as non-interned civilians of the same period.