"Inconvenient Truth" jokes aside, most people I've talked with the past few days were stunned by Al and Tipper Gore's separation after 40 years of marriage.

The couple's possible reasons -- infidelity? loneliness? public pressures at a breaking point? -- are none of our business, which makes this story irresistible. But their decision to split after four decades isn't unheard of. The divorce rate among long-time marrieds, while small, is creeping up.

A national AARP study, conducted in 2004, reported a rise in the divorce rate among people ages 40 to 79. That is corroborated by an Australian study, which found 28 percent of divorces in 2008 involved marriages of 20 years or more, up from 20 percent in 1990.

"That is the trend for sure," said Sherry Bronson, director of Twin Cities-based Daisy Camp (www.yourlifecraft.com), which offers weekend retreats for divorcing and divorced women of all ages.

"The last couple of camps have been decidedly comprised of more long-term marriages than before," she said. "Goodness, I was just with one gal last night who was splitting up after 37 years. Another woman came to a retreat who was 65 and had been married since she was 20. You do the math."

Barb Greenberg, who offers support groups to women divorcing after long-term marriages (www.rosepathpress.com), understands the eyebrow-raising around the Gore split. She was divorced after 33 years.

"Oh, darn it. They were the good guys," Greenberg said. "I can't imagine anything icky happened, but you don't know. From the outside, everything looks good."

The reasons for divorce after decades are as complex as a couple's dynamics. Some fall out of love, or "grow apart," as has been suggested about the Gores, who married young. He's 62, she's 61.

Some leave due to infidelity, or emotional and physical abuse. Many wait until the children are grown; 58 percent of men and 37 percent of women said they postponed divorce for five years or more for the sake of the kids.

Some partners are blindsided by the news that their spouse, typically the wife, is quitting the marriage. The AARP study noted that 66 percent of later-life divorces are initiated by women.

"When the woman perpetrates the split, she decides she just wants a different life, especially if they've reached the mature years," Bronson said. "The kids are gone, she asks herself, 'What am I doing?'"Many women who have not been in the job force face financial pressures post-divorce, but Bronson says men face their own demons. "I have had so many men contact me, saying, 'We need this [retreat] as much as women do.' They are equally in pain and in need of support."

They're men like Dave, 55, (who asked that I not use his last name). He was married for 31 years before his wife told him last summer, "You're out and somebody else is in."

Jan Borchers, of Edina, was married for 25 years before deciding to leave her marriage. "People were surprised because we had been married for so long. You're supposed to just stick it out." U.S. Census statistics show that most first-time divorces occur around year eight. Minneapolis family lawyer Brian Sobol says his divorcing clients are typically in the 10-to-20-year marriage range. But he does remember one woman divorcing after 50 years. "She asked to have her former name restored," Sobol said, "because her husband had been stepping out for years with a neighbor."

And, overall, the divorce rate is down, hovering closer to 43 percent than the typically reported 50 percent. Some of that decline is due to good news, such as people marrying later and staying together. But some troubled couples have had to put divorce on hold during this tough economy, forced to live under the same roof as tensions rise to sometimes unbearable levels.

But even the most amicable splits face tough sledding. "It's harder the longer you've been married," Borchers said. "You have this history together."

Bronson, a Bloomington real estate agent, agreed: "It's always traumatic, even if you are the one who wants the divorce. People who have not gone through divorce simply cannot understand the depth of the pain. You can agonize for years before you do anything."

While Dave was aware "that the other half was not happy, I was blindsided," he said.

Fighting the urge to crawl into the fetal position after his divorce, he forced himself to draw on the support of family and friends, get counseling and develop an action plan. He recently started dating a "wonderful, spiritual woman," and now believes that the best 20 years of his life are ahead.

"Al and Tipper? I was not surprised," Dave said, "because I was in a long-term marriage and, guess what? It happens."

Gail Rosenblum • 612-673-7350 • gail.rosenblum@startribune.com