Middle-aged Americans who are single or married with children from prior relationships find planning for retirement is tougher than it is for those with “traditional” families, a new study finds.

According to the MetLife Mature Market Institute’s “Family Matters” study, 40-to-65-year-olds with non-traditional families face more challenges with saving and investing and are less likely than are others to have a distinct retirement vision.

They are also less likely to have specific income vehicles, such as 401(k)s, pension plans and annuities.

Family structure largely influences how people plan for retirement, the study found. It addressed 3 specific mid-life segments: “traditional families” (2 parents with children from their current relationship); “blended families” (2 parents with at least one child from a previous relationship); and “single women” (widowed, divorced or never-married, with or without children).

“We should not be ignoring how former spouses, stepchildren and having no children influence savings and income for retirement as well as estate planning,” observes Sandra Timmermann, director of the MetLife Mature Market Institute, a division of MetLife Inc., New York.

The survey found that 66% of traditional families feel at least to some extent prepared for retirement, compared with 56% of blended families and only 40% of single women. And 55% of traditional families have a clear idea of what they hope to experience when they retire, compared with 48% of blended families and only 38% of single women.

Among both single women and blended families, more than 60% say it’s much harder for them to save for retirement. In fact, just 29% of blended families and 21% of single women consistently contribute to their retirement accounts, compared to 41% of traditional families.

Other survey findings:

42% of single women own 401(k)s, compared with 58% of blended families and 70% of traditional families. (Many single women with children work part time, and few employers set up 401(k)s for part time workers, MetLife points out.)

44% of traditional families have pension plans. And 17% have annuities, while blended families have 41% and 15%, respectively. Single woman have 26% and 11%.

19% of blended families and 18% of single women worry that they don’t have safeguards to ensure that an ex-spouse can’t lay claim to their income or to savings meant for themselves or their children.

Single women say they lack the safety net of a second income that their married peers have, the study reports. They are, therefore, more worried (38% vs. 27% of blended families and 23% of traditional families) that they will not have a set level of monthly income to last through their retirement.