。
Old age is an island surrounded by death.
Literal
Old-age [topic-は] death [by-に] surrounded island [copula-である].
A striking metaphor. 取り巻かれている is the passive of 取り巻く ('to surround'). ~である is the formal copula, fitting the literary register. The image of old age as an island besieged by death is poetic and memorable — likely a translated quotation.