Increased Dementia in Underweight Individuals

[Silverlining]

This study indicates increased dementia rates in <20 BMI. I'm underweight, according to these guidelines.

BMI and risk of dementia in two million people over two decades: a retrospective cohort study.

"Our cohort of 1 958 191 people from UK general practices had a median age at baseline of 55 years (IQR 45–66) and a median follow-up of 9·1 years (IQR 6·3–12·6). Dementia occurred in 45 507 people, at a rate of 2·4 cases per 1000 person-years. Compared with people of a healthy weight, underweight people (BMI <20 kg/m2) had a 34% higher (95% CI 29–38) risk of dementia. Furthermore, the incidence of dementia continued to fall for every increasing BMI category, with very obese people (BMI >40 kg/m2) having a 29% lower (95% CI 22–36) dementia risk than people of a healthy weight. These patterns persisted throughout two decades of follow-up, after adjustment for potential confounders and allowance for the J-shape association of BMI with mortality."

http://www.thelancet.com/journals/landi ... 9/abstract

[SusanJ]

I know, I saw that and thought, holy cow, so many of us here are low weight.

Can anyone see the full text to see if they looked at E4 effects? That's always my first question anymore...

[Julie G]

I'd love to see full-text as well. Scary. This corroborates an underlying theme that Martha and I received at our recent conference: sarcopenia drives neurodegeneration. Agnes Flöel, who has done some CR research did not recommend caloric restriction for high risk populations (like ours) for that reason. FWIW, she recommended CR mimetics instead- resveratrol & quercetin.

Makes me re-think things a bit Certainly, moderation in ALL strategies.

[Stavia]

its not on my library database yet.
I'm sceptical of them finding reduced incidence at higher BMI.

very obese people (BMI >40 kg/m2) having a 29% lower (95% CI 22–36) dementia risk than people of a healthy weight.

This study appears to be data extracted from General Practice records. There is no way that BMI is going to have been recorded consistently. It is possible that BMI has been recorded more regularly for the obese because we are always on at them, and not for the normal weight people.
This is not the way to collect data - they collected a dementia diagnosis only when BMI had been measured. And BMI is measured or not measured for a multitude of reasons. I work in a very similar environment and know what the GP records look like in a busy busy public health sector.

I will check again in a couple weeks to see if its on yet, and then we can see what the methodology and results were.
PS: And its not gonna have apoe4 status considered - the test didn't exist 20 years ago and it's not a general practice thing to do anyway.

PPS: I've been thinking about the middle road some more. I will add to my thread with my musings

viewtopic.php?f=7&t=687

[KatieS]

Good observation about BMIs,Stavia. Rarely do practices measure height, as opposed to recording what the person estimates, which for men can be a few inches taller than what they are. Of course, I would think they would have corrected for smoking or health issues associated with lower BMIs.

[Julie G]

Kit, hilarious that you would single out MEN as exaggerating their height...but kinda rings true.

Looking into this further; it's complicated. Smaller BMI is associated with symptom onset. Eating less (or refusal to eat) is a common AD manifestation. A larger body of work suggests that central adiposity (belly fat) at middle age is associated with dementia onset in older age. We know AD develops over decades. That understanding helps explain this current paper.

[pgf54]

[quoteEating less (or refusal to eat) is a common AD manifestation][/quote]

I think this is often true but usually when Ad has progressed to a more severe stage, often they are too pre occupied or too busy fidgeting to sit and eat ............although it may also be true if depression hits with insight in the early stages.........

There can be no comparison in my opinion of someone with a deliberately low bmi and optimal nutrition and someone attending a Drs surgery with a very low bmi..........There are so many reasons why their bmi may be low from drugs, alcohol, smoking, poor diet and nutrition, anorexia ,disease process with resulting cachexia, financial issues and so forth......

Incidentally Kitano my height is one of the few things i don't exaggerate.

[Stavia]

Incidentally Kitano my height is one of the few things i don't exaggerate.

So of course this begs an obvious question....
*Giggle*

Couldnt resist

[pgf54]

One thing i have learnt in life is to never exaggerate or lie to a GP as they will always find you out lol

[circular]

A larger body of work suggests that central adiposity (belly fat) at middle age is associated with dementia onset in older age.

And this is my conundrum. I really don't have much central fat (most would say I have none but most don't see me with my clothes off), but if I lost what's there the rest of me would be even more underweight/skinny than I already am. So what if we're underweight/skinny but have some mid-life bulge we should lose?

I think the answer must be to shed any extra fat while building more muscle and then not worry about the weight if it's a "healthy skinny". I'd like to know, for the skinny people in the study, what was their lean muscle mass? I'm thinking a lot of obese people may actually have quite strong muscles under their fat. I've sometimes thought about how much weight they are able to carry around (although it's obviously not good for joints and other reasons).