Autumn Sundowning: Why Dementia Gets Worse in September

The person you are caring for is worse this week than she was three weeks ago, and you cannot quite point to why.

She is up earlier in the afternoon than she used to be — restless by three-thirty, agitated by four, hard to settle by five. The evenings, which had been manageable through August, have started coming apart. She is not sleeping through the night. The mornings are foggier than they were. Nothing about the medication has changed. Nothing about the household has changed. And yet, undeniably, she is different.

If it is the last week of September, and you are reading this having noticed the shift, we can tell you what happened.

The light changed.

What is actually happening

The human brain runs on light. Every twenty-four hours, a bundle of cells in the hypothalamus called the suprachiasmatic nucleus receives light information from the eyes and uses it to set the body's circadian rhythm — sleep timing, hormone release, body temperature, alertness, appetite. This is happening in every human all the time; it is why jet lag exists, why night-shift workers develop specific health problems, and why the first week of daylight saving time in spring is measurably worse for cardiac events than the rest of the year.

The dementia brain runs on light more than a healthy brain does. As the internal clock deteriorates, the person becomes progressively more dependent on external cues to know what time it is, whether it is morning or evening, whether it is time to be alert or time to wind down. In a bright, consistent, well-lit environment, the dementia brain uses those cues to compensate. In a dim, ambiguous, transitional environment, it loses its footing.

September and October are the most transitional months of the year in most of the United States. In the third week of September, we lost about twenty minutes of afternoon daylight compared to the same date in August. By mid-October, we will be losing another twenty. The sun that used to be high and bright at 5 p.m. is now angled, low, and dimming. The cue that used to tell the brain it is still afternoon has stopped arriving on time.

Sundowning, in other words, is worse in September than in July for reasons that are physiological rather than psychological. It is not that your loved one is more anxious this month. It is that her brain has less light to work with, and the specific structure of her disease depends on that light more than yours does.

Why autumn is worse than winter

The counterintuitive piece is that mid-winter is often easier than early autumn.

Once the days are short and stable — say, mid-December through mid-February — the dementia brain adjusts to the new normal. Not perfectly, but functionally. What is difficult is the transition. The three or four weeks in September and October when the light is changing rapidly are worse for sundowning than the deep dark of January, because change itself is what the impaired circadian system cannot handle.

This has practical implications. If you white-knuckle through the next six weeks doing nothing, things will likely stabilize in November regardless. But that is a lot of hard afternoons to accept as inevitable, and there are three shifts worth making that meaningfully reduce the difficulty.

The three shifts

1. Bright light exposure in the morning, before 10 a.m.

The single most protective thing you can do for the dementia brain right now is give it a strong dose of morning light. Not medication. Not a supplement. Light.

Practical: get her outdoors, ideally, or seated by a large east-facing window, for at least twenty minutes within an hour of waking. In parts of the country where September mornings are already cool, a covered porch with a lap blanket works. If mobility or weather makes outdoors impossible, a light therapy box designed for seasonal affective disorder — ten thousand lux, positioned at eye level, used for twenty to thirty minutes during breakfast — produces measurable benefits in dementia sundowning specifically.

Morning light anchors the circadian rhythm for the entire day that follows. The intervention is early and its payoff arrives at 5 p.m.

2. Interior lights on earlier than feels necessary.

By 4 p.m. in late September, the indoor light level in most homes has dropped below the threshold at which the dementia brain reads "still daytime." The evening starts arriving in the room before the sun sets, and the brain responds by starting to wind down, get restless, and then get agitated when the wind-down doesn't complete.

The fix is to turn interior lights on earlier than you would in June. Not the overhead fluorescents — those can produce their own agitation — but warm-toned lamps, at seated height, distributed so that no corner of the room is markedly darker than another. Signal to the brain, artificially, that it is still afternoon. The signal works even when consciously she cannot articulate why the room feels calmer.

By the time the sun actually sets — around 6:45 in most of the U.S. this week — the household should already be softly, warmly lit for two hours. Then dim gradually into evening, on a schedule you set.

3. Move the afternoon anchor earlier.

We wrote at length earlier this month about the load-bearing importance of an anchor activity in the late afternoon window. In July, that anchor could be at 3:30 or 4:00 without issue. In late September, the whole window shifts earlier by roughly the same amount daylight has shifted — call it thirty minutes.

If she was calm doing a puzzle at 4 p.m. in July and is agitated doing the same puzzle at 4 p.m. now, the puzzle is not the problem. The clock is. Move the anchor to 3:15 or 3:30. Start earlier. Have the light already on. Have the mug of tea already poured before she gets restless.

Getting the anchor started before agitation begins is what changes the whole evening. Trying to start it once she is already climbing the walls does not work, and never has. Autumn just makes the window in which you have to start narrower.

What the anchor should look like

Because families reading this in the middle of a hard week will want the concrete answer:

Same chair, same table, same lamp, every day. The environment does more work than the activity.
Same mug of the same warm drink placed within reach before she sits.
Music playing softly — songs she was hearing between ages eighteen and twenty-five, which is the most preserved musical window in the dementia brain.
One activity in front of her, set out. Not a choice; one thing, ready.

For that one thing: a coloring page with a landscape she likes. A Picture Memory Card session — set two or three cards face-up, look at them together, put them away, get out three more. A printed large-format word search with an easy topic she enjoys. A basket of family photographs to look through without a testing question attached.

The activity does not need to be new or impressive. It needs to be the same. The dementia brain, deprived of internal time cues, is going to grip on to whatever external structure you offer. The offer should be reliable.

What to accept and when to call the doctor

There is a version of this piece where we tell you that these three shifts will make autumn sundowning go away.

They won't. They will reduce the severity of it — meaningfully, in most cases — and reduce the frequency of the worst evenings. That is a genuine and worthwhile improvement, and it is what the interventions in this piece can honestly do.

What they will not do is prevent the sundowning entirely, and if you have implemented the shifts above and she is still severely agitated most evenings, that is a signal to call her doctor rather than to try harder. Sudden or severe worsening in sundowning can be caused by a urinary tract infection, a new medication or dose change, undiagnosed pain, or another treatable underlying issue. A good geriatrician or the prescribing physician will screen for those before adjusting psychiatric medications.

And the honest reality: the six weeks between now and mid-November are just harder than most of the year in dementia caregiving. Not because of anything you are doing wrong. Because of the position of the earth relative to the sun, and the specific way an impaired brain relies on that geometry.

Do the three shifts. Accept the rest. The clock changes in early November, and the household will settle again.

You will make it through this.

Coloring pages and Picture Memory Cards are two of the most reliable afternoon-anchor activities in the library — designed for the same-chair-same-time window, low cognitive demand, no right answers to get wrong. Both print immediately. [Browse afternoon activities →]

This article is for general information and is not medical advice. A sudden or severe change in sundowning severity should be discussed with your physician, since underlying causes can include treatable conditions unrelated to disease progression.