According to the Oxford English Dictionary middle age is between 45 and 65: "The period between early adulthood and old age, usually considered as the years from about 45 to 65."
依照《牛津英語詞典》的定義，中年是在45歲到65歲之間階段：「是介於青壯年和老年之間的階段，約在45歲到65歲之間。