Expresses the meaning 'while', 'as', or 'since'.
Long explanation:
The ~ながらに grammar point is used to express the continuation of a state or condition. It often gets translated as 'while', 'as', or 'since' in English. The state or condition expressed by this grammar point usually continues for a long time after it first becomes applicable. It is mostly used with nouns and na-adjectives (minus 'na').