One study looked at women who were stably married, stably single, or gained or lost a partner during an eight-year period. The always-married women had the best sleep, followed by those who gained a partner. Those who lost a partner had the worst sleep. Another study found that while 26% of those earning $10,000 a year or less had sleep problems, only 8% of those earning more than $75,000 did. A study author speculated that poor sleep among lower income people might have to do with "illness, fewer support systems, depression, anxiety, dissatisfaction, lower quality of life," as well as "external factors" like "demanding work schedules, rotating shifts, family demands, limited access to healthcare, and unemployment."
A third study found that poor relationship quality resulted in worse sleep, and vice versa. A study author said,
When we look at the data on a day-by-day basis, there seems to be a vicious cycle in which sleep affects next day relationship functioning, and relationship functioning affects the subsequent night's sleep. In this cycle, conflict with one's partner during the day leads to worse sleep that night, which leads to more conflict the following day. [...] the woman's perception of the relationship seems particularly important, as it impacts both her own and her partner's subjective sleep quality that night.
The study author recommends never going to bed mad, or, you know, just having huge amounts of money.
Stable Marriage Is Linked With Better Sleep In Women [EurekAlert]
Socioeconomic Status, Gender And Marital Status Influence Sleep Disturbances [EurekAlert]
Poor Sleep Is Associated With Lower Relationship Satisfaction In Both Women And Men [EurekAlert]