Most sleep studies included only white men in the early years and other racial and ethnic groups and women and were not included in studies of sleep disorders until the 1990s, says Dr. Andrea Matsumura, a sleep medicine physician at The Oregon Clinic in Portland, Oregon, and a member of the Public Awareness and Advisory Committee at the American Academy of Sleep Medicine.

But the growing body of literature so far has revealed that sleep plays an important role in human health, and factors beyond an one’s control are linked to sleep problems, which can then affect overall health. Research also shows sleep deficiencies disproportionately impact those who experience other health disparities.

To take into account social, environmental and economic factors affecting sleep, researchers and experts use the term “sleep health” to create a holistic view of sleep.

“When I think about sleep health, I think about the right environment and the right amount of hours for sleep,” says Matsumura. “If the environment is too cold or too warm, or if you don’t have the right bedding, if you’re working three jobs to survive, or if don’t have money for a bed and you’re having to sleep in a chair, that’s going to affect your sleep health, because you’re not going to be able to get enough sleep.”