Tired after bad nights: menopause brain fog

Most of what this site covers happens in the dark. This page is about the day that follows: the walk into a room with no idea why you came, the word that will not arrive in a meeting, the slump at three in the afternoon. It sets out what is known about why the nights spill into the days, how much of the fog is the hormones and how much is the lost sleep, and which kinds of tiredness need a doctor to look for another cause.

Why a broken night shows up the next afternoon

The NHS lists mood changes, poor memory and brain fog among the symptoms of perimenopause and menopause, and adds that they may feel worse if you have sleep problems and feel very tired. Its general page on tiredness and fatigue names both not getting enough sleep and hormonal changes such as the menopause as common causes. In these years the two often arrive together.

Sleep research explains why the day suffers. A review of sleep-loss studies in Nature Reviews Neuroscience describes attention as one of the abilities most sensitive to short sleep: it becomes erratic, held for a while, lost, picked up again. Working memory, the mental notepad you use to hold a phone number or follow a conversation, slips with it. The deficit builds with each hour of lost sleep, and it adds up over a run of broken nights as well as after one night with no sleep at all.

The same review notes that people differ a great deal. In the lab, about a third of volunteers show little loss of attention after missed sleep and about a third show marked lapses, and the difference seems to be a stable trait. If you have always needed your full night, the broken ones of perimenopause will probably hit you harder than they hit a friend.

Menopause brain fog and sleep

The clearest link between night sweats and next-day memory comes from a small study by Pauline Maki at the University of Illinois at Chicago, published in the journal Menopause in 2008. She fitted 29 midlife women who had moderate to severe hot flashes with monitors that record a flash from changes in skin conductance, then gave them standard memory tests. In her account of the results, the women under-reported their hot flashes by about 40 percent compared with the monitors.

The more flashes the monitor counted, the worse the women did at remembering stories. Their own counts showed no such link, which is why earlier studies relying on diaries had missed it. Fewer hours slept and more flashes during sleep both predicted poorer memory the next day. Maki's reading was that something physical about the flash itself is involved, and that worry about having flashes does not explain it.

Twenty-nine women is a small group, and the study shows an association. It does fit the experience of many women who notice that a night of sweats is followed by a day of losing their keys.

Is it the hormones or the nights?

Probably some of each, and the hormonal part seems to pass. The Study of Women's Health Across the Nation (SWAN) gave 2,362 women aged 42 to 52 tests of verbal memory, working memory and processing speed over four years. A summary of the 2009 Neurology paper sets out what happened. Normally scores improve as people get used to repeating a test. In late perimenopause the gain in processing speed was only 28 percent as large as before periods started changing, and the gain in verbal memory fell to 29 percent in early perimenopause and 7 percent in late perimenopause.

After menopause, the learning came back to the level seen before the transition. The lead author, Gail Greendale, noted that 60 percent of women say they have memory problems during these years, and called the effect of perimenopause on learning temporary.

So a foggy patch in your late forties fits the pattern these studies describe, and the studies found it lifting. What the research cannot do is tell you which share of your own fog is the hormones and which is the 3am waking. The second share is the one you have some say over.

When the tiredness is something else

Feeling exhausted during perimenopause is common, but tiredness has many causes, and several of them become more common in exactly these years. The NHS advises seeing a GP if you have felt tired for a few weeks and are not sure why, if the tiredness affects your daily life, or if it comes with other symptoms such as weight loss, mood changes, or being told you gasp, snort or choke in your sleep. Its list of conditions that cause fatigue includes several worth knowing in midlife:

• Iron deficiency anaemia, with lack of energy, palpitations, shortness of breath and pale skin. The NHS names heavy periods as a very common cause, and periods in perimenopause can get heavier before they stop.
• Sleep apnoea, which leaves you tired in the day from waking at night, often with loud snoring. It becomes more common after menopause, and the signs women tend to miss are often insomnia and morning headaches more than snoring.
• Diabetes, with thirst, weight loss and peeing more often, particularly at night.
• Thyroid problems. The NHS tiredness page lists an overactive thyroid (restless, anxious, irritable, weak muscles), and NHS 111 Wales adds an underactive thyroid, which brings tiredness, muscle pain and weight gain.
• Depression and stress, which the NHS counts among the common causes of fatigue on their own.

A GP may suggest blood tests to check for anaemia, diabetes or thyroid trouble. Tell them about your periods, your nights and any snoring a partner has mentioned, because those details steer which tests make sense. Restless legs at night are worth mentioning too: the NHS lists them among the less common signs of iron deficiency, and the restless legs page covers the rest.

Getting through the day after a bad night

The NHS suggestions for tiredness are plain ones: keep the same sleep times and aim for 6 to 9 hours, give yourself a couple of hours to wind down, keep the bedroom from getting too bright, noisy or warm, and avoid caffeine, food and exercise in the couple of hours before bed. None of that removes a night sweat, but it protects the sleep you do get.

The day after a bad night is also when the night ahead gets set up. A long nap, an extra coffee at four and an early night spent lying awake can turn one rough night into a run of them. The menopause insomnia article explains how that pattern takes hold and what the trials found loosens it. If the waking comes in the early hours, why you wake at 3am covers the timing, and a cooler bedroom takes some heat out of the flashes that start it.

If you can choose when to do your hardest thinking, the sleep-loss studies give a reason to put it earlier in the day. Attention lapses grow with time awake, so a report written at ten is likely to cost less than the same report at four.

Writing down the days as well as the nights

Fog is hard to describe in a ten-minute appointment, and the Maki study is a reminder that memory of symptoms is unreliable, especially when you are short of sleep. A note each morning of how you slept and each evening of how the day went gives a GP something concrete. If the foggy days follow nights of sweats, that suggests one explanation, and foggy days after full nights suggest another.

The printable night diary has a row for each night. Add a line to each row for the day after: how foggy you felt, rated mild, moderate or severe, and anything you forgot or struggled with. Bring the sheets to the appointment, and the tracking and your doctor section has more on what to ask.

My take

I'd treat the daytime fog as a sleep problem first and a memory problem second, because that is what both the NHS and the studies point to, and it is the part you can work on. I'd start by tracking two weeks of nights and days together, so you can see whether the bad days really follow the bad nights. If they do not, or the tiredness has lasted more than a few weeks, I'd book the GP and ask about anaemia, thyroid and sleep apnoea before putting it all down to hormones. The insomnia and 3am waking section has the rest of what helps with the nights themselves.