BPPV happens when tiny calcium carbonate crystals inside your inner ear break loose from where they’re supposed to be and drift into one of the semicircular canals, where they don’t belong. These crystals, called otoconia, normally sit embedded in a gel-like membrane inside a structure called the utricle, where they help you sense gravity and linear movement. When they detach and float into the fluid-filled canals that detect head rotation, they trick your brain into thinking you’re spinning every time you move your head a certain way.
The cause isn’t always identifiable. But a mix of aging, injury, nutritional deficiencies, and other health conditions can weaken the structures holding the crystals in place or physically knock them free.
How the Crystals Work When They’re in Place
Your inner ear contains two otolith organs, the utricle and the saccule, that detect gravity and acceleration. Inside each one, hair-like sensory cells project into a gel layer topped by a fibrous membrane studded with otoconia. These crystals are denser than the surrounding fluid, so when you tilt your head or accelerate in a car, gravity pulls the crystal-weighted membrane in a specific direction. That movement bends the sensory hairs underneath, sending signals to your brain about which way is down and how fast you’re moving.
The crystals are held in the membrane by protein fibers. When those fibers weaken or the crystals themselves degrade, otoconia can detach. Once free, they usually settle into the posterior semicircular canal (the lowest one when you’re upright), though they can end up in any of the three canals. In over 98% of BPPV cases, the crystals float freely in the canal fluid. In rare cases, they stick directly to a motion-sensing structure at the end of the canal called the cupula, which can make symptoms last longer and respond less well to treatment.
Aging Is the Most Common Factor
BPPV becomes dramatically more common with age. The one-year prevalence in people over 60 is roughly seven times higher than in adults aged 18 to 39. By age 85, nearly half of all people experience vestibular symptoms including dizziness. In one study of people over 70, almost 40% were diagnosed with BPPV, and separate screenings in geriatric populations found 9% had unrecognized BPPV they didn’t even know about.
Several things happen inside the inner ear as you get older. The number and volume of otoconia gradually decrease over a lifetime, and the protein fibers connecting them to the membrane weaken through a process of demineralization. At the same time, the chemical environment of the inner ear fluid shifts. Changes in pH and calcium concentration make the crystals less stable. The result is a slow, cumulative loosening that explains why so many older adults develop BPPV without any obvious trigger.
Head Trauma and Mechanical Forces
In a large study of 500 BPPV patients, trauma was the most common identifiable cause, accounting for 16% of cases. A blow to the head creates shearing forces strong enough to physically rip otoconia from the membrane. This doesn’t require a skull fracture. Rapid deceleration, like in a car accident or a fall, generates enough rotational stress on the inner ear structures to dislodge crystals even without direct impact to the temporal bone.
Post-traumatic BPPV can appear shortly after injury or develop over the following weeks as loosened crystals gradually migrate into a canal. People who’ve had a traumatic brain injury face a meaningful risk: roughly 15% of patients who experience vestibular neuritis (an inner ear nerve inflammation, which can also follow illness or infection) go on to develop BPPV afterward, likely because inflammation damages the membrane holding the crystals.
Low Vitamin D and Poor Bone Health
Because otoconia are made of calcium carbonate, anything that disrupts calcium metabolism in the body can affect their stability. Vitamin D plays a central role here. It regulates how your body absorbs and uses calcium, including the calcium turnover that maintains otoconia structure. A large meta-analysis found that people with BPPV had significantly lower vitamin D levels than people without it. The gap was even wider for people with recurring BPPV, whose vitamin D levels were on average about 5 ng/mL lower than those who had a single episode.
Low vitamin D appears to impair the inner ear’s ability to maintain and repair its crystals. Without enough calcium being properly deposited, the otoconia’s internal structure weakens and their attachment to the membrane deteriorates. This helps explain why BPPV tends to recur in certain people: their underlying mineral metabolism keeps destabilizing new crystals.
Osteoporosis follows the same logic. Multiple studies show a clear correlation between low bone mineral density and both the occurrence and recurrence of BPPV, especially in women over 45. Patients with osteoporosis needed more treatment sessions to resolve their BPPV and were significantly more likely to have it come back. The relationship between bone density loss and BPPV recurrence appears to get stronger as bone mineral density decreases, and the risk climbs further when osteoporosis is combined with conditions like hypertension or diabetes.
Dental Work and Prolonged Positioning
One of the more surprising triggers is dental work. A population-based study found that three types of dental procedures significantly increased BPPV risk: periodontal treatment (gum procedures) raised the odds by about 3.4 times, oral surgery by 2.2 times, and prosthodontic work (crowns, bridges) by 1.6 times. Two mechanisms are likely at play. The vibration and tapping from dental tools, particularly instruments called osteotomes, can transmit enough force through the skull to shake crystals loose. But the positioning matters too: repeatedly sitting up and lying back in a dental chair, sometimes with your head angled below horizontal, may be enough to displace otoconia that are already loosened.
Prolonged bed rest works through a similar mechanism. Staying in one position for an extended period may gradually loosen otoconia, and the process of getting up afterward can send them into a canal. This is why BPPV sometimes appears after surgery, hospitalization, or any illness that keeps someone lying down for days.
Migraine and Inner Ear Blood Flow
People with migraines face a higher risk of developing BPPV, though the exact connection is still being worked out. The leading theory involves blood flow. Migraine is associated with vasospasm, temporary narrowing of blood vessels, including the tiny vessels that supply the inner ear. Repeated episodes of reduced blood flow may damage the delicate tissue lining the utricle, weakening the attachment points where otoconia are anchored. Animal studies have also found that migraine triggers neurogenic inflammation in the inner ear, and repeated bouts of this inflammation could accelerate degeneration of the otolith organs over time. In one study, people with migraines who also had coronary artery disease had a 4.6 times higher risk of developing BPPV, supporting the idea that vascular problems are a key part of the link.
Why BPPV Keeps Coming Back
Even after successful treatment, BPPV has a notable recurrence rate. About 10% to 18% of people experience a relapse within the first year. At five years, the recurrence rate reaches roughly 22%, and over a ten-year span, about half of all treated patients will have at least one more episode. Among those who do recur, about 70% relapse within the first year after their previous episode.
Recurrence tends to be driven by the same underlying conditions that caused the first episode. If the root issue is age-related degeneration, low vitamin D, or osteoporosis, new crystals will keep loosening over time regardless of how many times the displaced ones are successfully repositioned. This is why addressing modifiable risk factors, particularly vitamin D levels and bone health, matters for people who experience repeated bouts. The displacement itself is a mechanical event, but the conditions that make it happen are often systemic and ongoing.