Brain Health and inflammation?
There are not many dinner tables where one sister talks about deep sleep architecture and the other about the bacteria living below the gumline, and where both turn out to be describing the same problem from different ends. Ours is one of them. Isabella and I have spent years working in fields that most people file in entirely separate drawers, hers in the dental chair and mine in the bedroom, and for a long time we treated them that way too. Then the research caught up with the conversation we kept having anyway, and it turned out the mouth and the sleeping brain have been talking to each other all along.
The short version, for anyone who wants it before the detail, is this. Poor sleep, gum disease, and a faster-aging brain are increasingly understood as one connected story rather than three separate worries, and the thread running through all of them is inflammation.
Laura: Let me start where most people would not expect a sleep counsellor to start, which is your territory. When did you first realise that what happens in someone's mouth might be affecting how they sleep, and even how their brain ages, and vice verca?
Isabella: Later than I would like to admit. In dental training you learn the mouth as its own closed system, teeth and gums and the structures around them, and the rest of the body is someone else's department. What changed it for me was seeing the same patients turn up with severe gum disease and exhaustion written all over them, and slowly understanding that these were not two coincidences sitting in the same chair. Gum disease is not just a local problem. The inflammation it produces does not stay politely in the mouth. We now know that periodontitis, the chronic inflammatory disease that damages the structures holding the teeth, is increasingly recognised as a contributing factor to systemic conditions, including Alzheimer's disease.
Laura: That word, inflammation, is where our two worlds meet. From the sleep side, chronic low-grade inflammation is one of the quiet saboteurs. It disrupts the normal rhythm of sleep, and poor sleep in turn raises inflammation, so people get caught in a loop where each problem feeds the other. When you tell me that untreated gum disease is sending inflammatory signals into the bloodstream every night, I hear a sleep disruptor that most people never think to look for.
Isabella: And the loop you are describing has a third party in it, which is the brain. There is a specific mechanism researchers keep returning to. A keystone bacterium in gum disease, Porphyromonas gingivalis, has been detected in the brain tissue of people who had Alzheimer's disease, and it has been implicated in the hallmark features of the disease, including the accumulation of amyloid beta and the tangling of tau protein. The way it appears to travel is almost troubling in how direct it is. These bacteria produce enzymes called gingipains that can compromise the blood-brain barrier, the brain's protective border, allowing the bacteria and their inflammatory messengers to enter the central nervous system.
Laura: I want to be careful here, because this is exactly the kind of finding that gets overstated.
Alzheimers and the connections
Isabella: You are right to be, and I would say the same to any patient. The honest framing is that these are strong and growing associations, not a closed case of cause and effect, so I would never tell someone that flossing will prevent dementia. But the direction of the evidence is consistent. A 2024 meta-analysis on the impact of periodontal disease on cognitive disorders and dementia, and a large national survey the same year, both pointed the same way, that periodontal inflammation is associated with an increased risk of cognitive decline and Alzheimer's dementia. And there is a hopeful side to it that I think matters more. Studies have suggested that periodontal treatment might reduce the brain atrophy linked to Alzheimer's.
Laura: And the sleep side has its own version of that mechanism, which has been one of the most exciting areas of brain science in the last decade. While we sleep, the brain runs something like a nightly cleaning system, the glymphatic system, that helps flush out metabolic waste, including the very amyloid and tau proteins Isabella just mentioned. In a randomised crossover trial in humans published recently, normal sleep increased the morning clearance of these Alzheimer's-related proteins compared with a night of sleep deprivation, supporting the idea that sleep-active processes help move this waste out of the brain.
Isabella: Though I gather even that is being debated now.
Laura: It is, and I think it is healthier to say so than to pretend the science is settled. There is a genuine scientific debate underway about whether this brain clearance is most efficient during sleep or during wakefulness, with researchers presenting both cases. What is not really in dispute is the epidemiology that sits above the mechanism. Sleep disruption is consistently associated with increased Alzheimer's risk, and in people who are still cognitively healthy, short and poor-quality sleep is linked to greater amyloid and tau burden, even before any symptoms appear.
Obstructive sleep apnea
Laura: There is one condition that sits right on the border between your work and mine, and I think it deserves its own moment. Obstructive sleep apnea.
Isabella: It is the clearest example of why a dentist should care about sleep. In obstructive sleep apnea the airway repeatedly collapses through the night, and people tend to breathe through the mouth, which dries it out, and a dry mouth loses the protective wash of saliva that keeps bacteria in check. So you see a meaningful overlap between sleep apnea and serious gum disease. I am often one of the first people positioned to notice the signs, because I am looking inside the mouth regularly. Worn teeth, a dry mouth, a particular pattern of wear can all be quiet flags. A dentist who is paying attention can be the one who says, the way you are sleeping might be worth investigating.
Laura: Which is exactly the kind of catch that changes lives, because so much apnea goes undiagnosed for years. From my side, the things I would ask people to watch for are the ones a partner usually notices first, loud snoring, or those frightening pauses where the breathing seems to stop and then restart with a gasp. Those are not just noise. They are worth taking to a doctor.
Isabella: So if we are giving people something to actually do, where do you want to start?
Laura: With the parts that are genuinely within reach, because that is where the encouragement lives. On the sleep side, the foundations are unglamorous and they work. A consistent wake-up time, the same one every day, anchors the whole rhythm more powerfully than almost anything else. Keep daytime naps short, under twenty minutes, and earlier rather than later in the day. Be honest about caffeine in the afternoon, since it lingers far longer in the body than people assume. And give yourself a real boundary with the phone before bed, both for the light it throws and for the way it keeps the mind switched on at exactly the hour it needs to power down.
Isabella: And mine is even simpler to say, though people resist it just as much. Brush thoroughly twice a day and actually floss, every day, not the night before the dentist. The point is not vanity. Good daily oral hygiene is what keeps gum disease from progressing, and that matters because periodontal screening, prevention, and timely treatment are increasingly seen as relevant for people at risk of cognitive decline. It is one of the few genuinely simple things you can do each day that reaches far beyond the place you are doing it.
Laura: I think that is the thread worth leaving people with. Not that any one habit is a cure, but that sleep, the mouth, and the brain are not separate projects. They are one system, and tending to any part of it gently supports the rest.
Isabella: Which, I suppose, is also a fair description of being sisters. Two people working on what looks like different things, who keep discovering they were solving the same problem the whole time
Laura Kanadel is a certified sleep counsellor and the founder of MUUN and The Sleep Institute. Isabella Kanadel is a practicing dentist in Hørsholm. They are sisters.
A note on the science. The links between sleep, periodontal disease, and brain health described here draw on a growing body of international research, including work from the University of Sydney's Charles Perkins Centre and Brain and Mind Centre, alongside recent reviews and trials in journals including Nature Communications, Frontiers in Aging Neuroscience, and GeroScience. Much of this evidence is associative, meaning these factors travel together and share common biological pathways, rather than proving that one directly causes another.
