Poor short term memory: cause, what research measures and what a brain fog scan shows you

In this article you can read what research measures behind a poor short term memory, cause by cause: what one short night, burnout, a low mood, some medicines and years of eating do to it, and what a complaint about your own memory does and does not predict. That matters, because most pages stop at the question of whether forgetting is normal, while the causes that come with numbers are exactly the causes you can look at this week. The BioProfile brain fog scan measures how much you notice of memory and concentration complaints, and gives you an indication of where you stand today in this area, as one of the 11 health areas the full scan assesses. This is not a diagnosis. It is self-insight, to see where you stand today, and to help you make better choices in your food and lifestyle. What this scan does not do: point to a cause or make a diagnosis. Only a doctor can do that.

Poor short term memory: cause, age and what your own complaint says

Thuisarts puts the part about age simply: as you get older, your memory works a bit more slowly, and that is the case for many people.⁠⁵

Your own complaint has been followed for years. Across 21 studies with 22 cohorts and 47,805 participants at the start, people who themselves reported cognitive decline had a relative risk of 2.12 (95% CI 1.75 to 2.58) of a later, objectively measured cognitive disorder, over an average of 5.4 years of follow-up (range 2 to 18 years). Pooled per outcome that was 2.16 (95% CI 1.63 to 2.86) for dementia and 2.29 (95% CI 1.66 to 3.17) for cognitive impairment.⁠¹ The authors read this as a risk marker of roughly double. The complaint is self-reported and the outcome is measured years later, so the number describes groups over years.⁠¹ For one person it predicts nothing. It is a good reason to say the complaint out loud at the practice instead of waving it away.

The night before weighs heaviest

Two meta-analyses separated the night before learning from the night after. Sleep deprivation before learning gave a pooled effect on memory of Hedges g = 0.621 (95% CI 0.473 to 0.769), from 31 reports, 55 effect sizes and 927 participants, over literature from 1989 to 2020. Deprivation after learning was smaller: g = 0.277 (95% CI 0.177 to 0.377), from 45 reports, 130 effect sizes and 1,616 participants, literature from 1994 to 2020. Both are about total, acute sleep deprivation in experiments, so the numbers describe one night of sleep deprivation around a moment of learning.⁠²

In plain words: the night before you take something in weighs more heavily than the night after, and a name that will not come to you the morning after a bad night is the most ordinary cause on this list.

Burn-out and a low mood hit speed first

Across 17 studies with 730 patients with clinical burn-out and 649 healthy controls, short term memory and working memory were lower in the burn-out group (g = -0.36, 95% CI -0.52 to -0.20), episodic memory sat at g = -0.36 (95% CI -0.57 to -0.15), attention and processing speed at g = -0.43 (95% CI -0.57 to -0.29) and verbal fluency at g = -0.53 (95% CI -1.04 to -0.03). On crystallised ability (6 studies) and visuospatial ability (4 studies) there was no difference between the two groups.⁠³

In depression, measured during a current episode against control groups, the deficits in executive functioning, memory and attention ran from d = -0.34 to -0.65; in remission, executive functioning and attention were still off (-0.52 to -0.61), while the memory effects (-0.22 to -0.54) were not significant. The authors call cognitive impairment a core feature of depression that outlives the mood episode.⁠⁶

A Dutch measurement gives the scale of this in a general population. Among 4,734 participants aged 40 to 75 (mean 59.1, SD 8.6), measured between November 2010 and January 2018, depressive disorder had no significant link with the memory score (B = -0.02, 95% CI -0.15 to 0.11), while information processing speed was lower (B = -0.18, 95% CI -0.28 to -0.08) and the same held for executive functioning and attention (B = -0.13, 95% CI -0.25 to -0.02). The chance of cognitive impairment in general was higher: OR 1.60 (95% CI 1.06 to 2.40).⁠⁷

Read together, these three say something useful: what stress and a low mood take away first is speed and attention, and “my short term memory is bad” is often how slower attention feels from the inside. Thuisarts names tension and major life events, and being low or having a depression, among the things that make forgetfulness worse.⁠⁵

Medicines and alcohol

Thuisarts names 6 things that can make forgetfulness worse: tension and major life events; being low or having a depression; some medicines, such as sleeping pills and medicines for depression; some medicines for urine loss and an enlarged prostate; alcohol; drugs.⁠⁵

For one of those groups there is a measurement. Across 13 studies with 26,033 participants of 60 years and older (average age 72.5 years in the cohort studies, 83.8 years in the cross-sectional studies), people who use benzodiazepines regularly did not differ from controls on the memory test (SMD -0.04, p = 0.41, n = 2,580), while processing speed was clearly lower (SMD -0.61, p < 0.0001, n = 253). General cognition on the MMSE was lower in people who misused benzodiazepines (SMD -0.23, p = 0.02, n = 7,726); in people who use them regularly that difference was absent (SMD -0.05, p = 0.85, n = 1,536).⁠⁸

Here too it is about speed rather than about the memory test itself. If a sleeping pill or another daily medicine is on your list, you discuss this with whoever prescribed it.

Vitamin B12, and eating over decades

The recommended daily amount of vitamin B12 is 2.8 micrograms a day for everyone aged 18 and over. B12 is only found in animal products, so vegans are a risk group, and so are older people, because stomach acid production falls with age; absorption can also fall short if there is too little intrinsic factor. Complaints the Voedingscentrum names with a deficiency are tiredness, dizziness, palpitations and ringing in the ears, plus tingling in the fingers, memory loss, coordination problems and loss of strength in the legs.⁠⁹

That is a deficiency. Extra B12 without a deficiency is a separate question: across 16 randomised controlled trials with 6,276 participants with a mean age of 66 to 82 years, in people without a clear deficiency the memory effect was g = 0.028 (95% CI -0.011 to 0.067), general cognition g = 0.061 (95% CI -0.001 to 0.123) and the executive domain g = 0.06 (95% CI -0.021 to 0.141), with the literature searched up to June 2020. The meta-regression found no link with the B12 level at the start, the dose or the duration.⁠⁴ So the pill is worth something if there is a deficiency, and whether there is one is a blood value that a doctor requests.

Eating over the years is a slower story. In the Doetinchem Cohort Study, 3,644 Dutch participants (51% women) aged 45 to 75 at the start were measured in 6 rounds over up to 20 years, with a median follow-up of 15 years. The highest tertile for following the dietary guidelines showed an about 7% slower general cognitive decline between 55 and 75 years of age (range 6.5% to 7.4%) than the lowest tertile, and at 65 the difference came down to about 2 years of cognitive age for general cognition and 2.1 to 2.4 years for memory performance. The dietary indexes were linked with the level of memory performance, while the change in memory over the follow-up stood apart from both indexes.⁠¹⁰

Two years of cognitive age is a real difference and a slow difference. Eating by the guidelines shows itself over decades rather than in your memory next week.

When to contact the doctor

Thuisarts names 5 reasons to call the practice or make an appointment on a working day: you think your memory is going downhill quickly; your complaints get in the way of the ordinary things you do in a day; your complaints keep getting worse and it is not how it was; you think you have more trouble with your memory than other people do; you think you are getting dementia.⁠⁵

What a brain fog scan measures

The brain fog scan asks about the past two weeks: how often you notice that you forget something, search for words and lose your concentration, and how much that gets in the way of your day. Your answers become a score for this area and the reading band the score falls in.

What a questionnaire cannot do is name a cause. A short night, a burn-out, a low mood, a benzodiazepine and a low B12 all read the same in a list of questions.⁠^2,8 Blood values and a doctor’s assessment are the layers that turn a complaint into an explained picture. The scan is not a diagnosis. If you use the word brain fog for all of this instead of memory, the background is in what brain fog is and where it comes from.

In summary

Growing older makes memory work a little more slowly in many people.⁠⁵ A complaint about your own memory is a risk marker of roughly double over an average of 5.4 years and not a statement about one person.⁠¹ One night of sleep deprivation before learning weighs more heavily than the night after.⁠² Burnout and depression first pull attention and processing speed down, and the memory score follows less clearly.⁠^3,6,7 Benzodiazepines lowered speed rather than the memory test.⁠⁸ A B12 deficiency comes with memory complaints, while extra B12 without a deficiency did nothing measurable.⁠^9,4 Eating according to the guidelines showed up over decades as roughly 2 years of cognitive age.⁠¹⁰ Thuisarts gives 5 reasons to report it to the practice.⁠⁵ A scan gives you a baseline, and the rest can only come from a doctor.