Rising rates of loneliness may not be news, but the three periods when it peaks may come as a surprise: More people reported feeling moderate to severe loneliness during their late 20s, their mid-50s and their late 80s than in other life periods, according to research published Tuesday in the journal International Psychogeriatrics.

Dr. Vivek Murthy, former US surgeon general, says the reduced life span linked to loneliness is similar to smoking 15 cigarettes a day, Jeste noted in the study’s introduction. Meanwhile, some research suggests that loneliness is common in old age, and others say it is typical in young age. “They are somewhat split, so that’s what we wanted to find out,” Jeste said.

A total 340 San Diego County residents between the ages 27 and 101 participated in the study.

Jeste and his co-authors hypothesized that these community-dwelling participants, none with serious physical or psychological ailments, would report more loneliness in old age based on the “usual assumption that as people get older, they become more alone,” he said. They were surprised when they discovered two peaks (during the late 20s and mid-50s) in addition to the one in the late 80s. The results do not explain the reasons why people feel lonely, but Jeste had his theories.

“So the late 20s is often a period of major decision-making, which is often stressful because you often end up feeling that your peers made better decisions than you did, and there’s a lot of guilt about why you did this or did that,” he explained. It’s a period of stress, which increases loneliness, he said.

“The mid-50s is the midlife crisis period,” Jeste said. Typically, your health begins to decline, and many people learn that they have pre-diabetes, say, or heart disease.

The surprising main finding of the study was the 76% prevalence of moderate to severe loneliness, Jeste said: “We thought that it would be little more than a third.” Men and women felt equally lonely and to the same degree — no sex differences were found in either prevalence or severity, he and his colleagues found.

The third main finding, the inverse relationship between loneliness and wisdom, was “surprising and interesting and actually positive — an optimistic finding,” according to Jeste. He and his colleagues measured the six components of wisdom in each participant: general knowledge of life; emotion management; empathy, compassion, altruism and a sense of fairness; insight; acceptance of divergent values; and decisiveness — the ability to make quick, effective decisions when necessary.

The traits we need to develop