Yesterday, I posted a sneak preview of my take on a report claiming that singles are at risk for Alzheimer's. Here's my more detailed analysis.

Say it ain't so, BBC! Did you really report the singles-bashing headline, "Singles face Alzheimer's risk"? I'd only call it singles-bashing if this turned out to be still another matrimanical scare story, with little basis in science. So let me explain, BBC, why even you have been mugged by the Marriage Mafia.

The people in the Alzheimer's study were 1,432 Finns who had been recruited into the study in mid-life, then evaluated for cognitive impairment about two decades later when they were between 65 and 79 years old. Alzheimer's made the headline, but the study was about a variety of cognitive impairments, most of them mild. Of the 1,432 people in the study, 139 had some sort of cognitive impairment; only 48 had Alzheimer's.

Those who were widowed had 6 times the rate of cognitive impairment (all kinds) as those who were married. The divorced had 3 times the rate, and those who had always been single had twice the rate.

I wondered how many people we were actually talking about here, so I scoured the web for other accounts of this study and found more information. (Ordinarily, I go to the original scientific report, but this research has been described only in a talk given at a conference. The work has not been peer-reviewed, which should have been another warning to the BBC.) The vast majority of the people in the study (1,147 of the 1,432) were married. There were 111 who were always single, 63 who were divorced, and 111 who were widowed.

Crunching the numbers (see the statistical note at the end), that means that of those people in the study who had always been single, the number who had some form of cognitive impairment was about 14. For the divorced, it was about 12, and for the widowed, about 41. The others (about 71) were married. So yes, people who had always been single had a higher rate of cognitive impairment than people who were married, but we are talking about 14 people.

The headline was not about all forms of cognitive impairment, though - it was about Alzheimer's. Only 34.5% of all of the impairments were Alzheimer's. So of those people in the study who had always been single, how many had Alzheimer's? About 5, give or take. About 4 of the 63 divorced people had Alzheimer's and 14 of the 111 widowed people; the other 25 (approximately) were married.

Here's something I found in a different report of the findings that the BBC did not bother to mention at all:

"The association with an increased risk of Alzheimer's disease did not reach statistical significance."

Translation: the findings weren't really there. Scientifically speaking, any differences between the people of different marital statuses could have been due merely to chance.

With no reliable differences in the rate of Alzheimer's between the married and the single people, the BBC should not have heralded the "findings" in a headline. But it did that and more - inviting the author of the conference paper to speculate on why the married people were less at risk.

"This study points to the beneficial effects of a married life," said Krister Hakansson.
Anyone who has taken a beginner's course in research methodology knows that the study does no such thing. Even assuming that the author is referring to all cognitive impairments (for which there were differences) and not just Alzheimer's, he cannot know whether being married caused people to have lower rates of impairment, or whether the particular people who married would have had lower rates even if they had stayed single.

Still, with the BBC's encouragement, the author continued to explain why married people are less at risk: "Living in a couple relationship is normally one of the most intense forms of social and intellectual stimulation."

If you are a matrimaniac, you might accept that without question; after all, it sounds plausible, right? Personally, I'd bet on people (whether single or married) participating in collaborative work groups, on research teams, or in grassroots social movements as having more intense social and intellectual stimulation that a couple in their 70s who have been married for decades. I'd even go with pairs of close friends. But I'm just riffing here. In a poll of older couples in the UK, just under a third "felt challenged or stimulated in their relationship." Six percent said they did not talk to one another at all!

A different report of the dementia study was even worse than the BBC's in the lessons it drew from the research. The opening line was, "If you are single and in your 40s, it might be a healthy idea to get hitched."

Just to play along, I'm going to take this suggestion seriously. Let's say I've always been single. (It is true.) Let's also go with the author's undemonstrated assumption that marital status causes dementia. Let's also pretend that the differences in rates of dementia among the various marital status groups are statistically reliable (which, for Alzheimer's, they are not). That means that if I stay single, I have about double the chance of developing dementia in later life than someone who marries and stays that way. Some of those married people, though, will divorce after the study has ended and the researchers are no longer following them around. Those divorced people will now have a higher rate of dementia than I would by staying single.

Even those who marry and never divorce will not stay in their marital status forever. Half will become widowed. Then they will be way more likely to develop dementia than I will by staying single. But maybe you will be the partner who dies first - then you would keep your favored status as least likely to develop dementia throughout your life. Of course, unlike the spouse who outlived you and then became more at risk for dementia, you'd be dead.

Bella DePaulo is the author of Singled Out: How Singles Are Stereotyped, Stigmatized, and Ignored, and Still Live Happily Ever After.

[Statistical note: Because so little information was provided, I had to figure out the numbers myself. Here's how I did it. I started with the facts that were reported. There were 1,432 people in the study, and of those, 1,147 were married. Of all of the people in the study, 139 had some sort of cognitive impairment (most of it mild). Those who were always single had twice the impairment rate of the married, the divorced had 3 times the rate, and the widowed had 6 times the rate. Running those numbers, I found that if the rate of cognitive impairment among the married were 6.2%, then 71 of the 1,147 married people would be cognitively impaired. The rate is double for the always-single, so 12.4% of the 111 would be cognitively impaired, or 14 people. The rate for the divorced is 3 times that of the married, so 6.2% X 3 = 18.6% or 12 divorced people. For the widowed it was 6 times the rate for married, so 37.2% or 41 people. 71 married + 14 always-single + 12 divorced + 41 widowed adds up to 138, within rounding error of the 139 reported by the BBC and in other news reports. As for Alzheimer's, only 48 of the 139 cases of cognitive impairment, or 34.5%, were Alzheimer's. (The others were milder forms of impairment.) So, 34.5% of the 71 married people equals about 25 with Alzheimer's; 34.5% of the 14 always-single people equals 5 with Alzheimer's; 34.5% of the 12 divorced people equals 4 with Alzheimer's; and 34.5% of the 41 widowed people equals 14 with Alzheimer's. 25 married + 5 always-single + 4 divorced + 14 widowed equals the 48 total with Alzheimer's reported in the media.]

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