His theories, initially published in the New York Medical Journal, helped lay the groundwork for the modern study of ageing and elder care.

[4][5] Nascher also wrote a book focused on urban poverty, The Wretches of Povertyville: A Sociological Study of the Bowery, published in 1909.

[4] Nascher's work contained the argument (described as a "typical example" of racist attitudes of the time by academic Mara Keire) that opium addiction was required for white prostitutes to find sex with Chinese-American johns endurable.

[10] Nascher may have been inspired by developments in geriatric care in Austria, which he witnessed during repeated visits, including Arnold Lorand's 1910 book Old Age Deferred.

[2][4] Nascher argued that "senescence is not due to any one cause" and that "disease is not (always) a causative or even an essential factor", views which are now widespread among gerontologists.

[2][3] A retrospective review of the book, published for its 100th anniversary in 2014, described its "pleasing, rambling tone," and noted Nascher's prescient view of functional capacity.

The reviewer compared the book (in relation to the field of gerontology) to a Ship of Theseus, which set in motion the whole area of study, but of which only "a few of the original timbers remain".

[4] However, in 1931 he successfully pushed to become leader of the City Farm Colony medical facility on Roosevelt Island, which later became Coler-Goldwater Specialty Hospital.

[6][13] Nascher wrote that he hoped "to change the antiquated methods dealing with aged public dependents," and credited himself with focusing on their revitalization and rehabilitation.

[8] Nascher and his wife, Augusta, traveled extensively in Europe, Asia, and South America, and also took an annual trip to Poughkeepsie in upstate New York.

[8] Beginning in the late 1930s, as his wife's mental condition declined, Nascher cared for her with "devotion" and also kept notes, which he developed into his last published paper, "The Aging Mind.