FRIDAY, Feb. 5, 2016 (HealthDay News) -- The influence of a husband or wife on their spouse's quality of life remains strong even after death, a new study says.

Couples who have been married a long time develop a high level of interdependence, and one partner's quality of life at death continues to influence the survivor, the University of Arizona researchers said.

"If your partner has higher quality of life before they pass away, you're more likely to have higher quality of life even after they're gone. If he or she has lower quality of life before they pass away, you're then more likely to have lower quality of life," lead author Kyle Bourassa, a psychology doctoral student, said in a university news release.

The researchers examined data from thousands of older couples in 18 European countries and Israel taking part in an ongoing study of health, aging and retirement. Specifically, the researchers compared 546 couples in which one partner had died and 2,566 couples in which both partners were still alive.

There was no difference between the two groups in the strength of the quality-of-life interdependence, according to the study published recently in the journal Psychological Science.

"Even though your marriage ends in a literal sense when you lose your spouse, the effects of who the person was still seems to matter even after they're gone. I think that really says something about how important those relationships are," Bourassa said.

This ongoing connection after death is likely due to the thoughts and emotions a person has when thinking or talking about a deceased spouse, according to the researchers.

The findings could prove valuable for end-of-life care and for helping people who have lost their spouses.

"Relationships are something we develop over time and they are retained in our mind and memory and understanding of the world, and that continues even after physical separation," said study co-author Mary-Frances O'Connor, an assistant professor of psychology who specializes in grief and the grieving process.

"If you can boost someone's quality of life before they pass, that might affect not just their life, but the quality of life of their partner and their family," Bourassa said.

More information

The U.S. National Institute on Aging discusses mourning the death of a spouse.