After being embraced early on by young adult men in the US, e-readers have become increasingly popular among women and older adults, according to a new report by Nielsen. Though tablet ownership is still dominated by men, growing numbers of older Americans are buying the portable devices.

Some 61% of e-readers were owned by women as of the second quarter of 2011, compared with 46% in the 3Q10 (roughly nine months earlier).

That may explain why some publishers of women's magazines (e.g., O, The Oprah Magazine, Cosmopolitan, and Women's Health) have reported stronger sales via the Barnes & Noble Nook vs. the Apple iPad.

Smartphone owners are now evenly split between women and men, whereas tablet ownership is dominated by men (57%), although less so than nine months earlier, when men owned roughly 61% of all tablets.

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But tablet ownership demographics are shifting: In 3Q10, 62% of tablet owners were under age 34 and a mere tenth of tablet owners were older than age 55. Now, only 46% of tablet owners are younger than age 34 and 19% are age 55+.

Similarly, e-reader owners are getting older: 51% of e-readers are now owned by adults age 45 and above, compared with 40% in 3Q10.