Can COVID-19 Cause Permanent Loss of Smell?

Losing your sense of smell, known medically as anosmia, can greatly impact your quality of life. Our ability to smell allows us to enjoy flavorful foods, detect danger like gas leaks or smoke, and form emotional connections through scents. For those recovering from COVID-19, a lingering loss of smell is concerning. Can this common post-COVID symptom become a permanent condition?

Why Smell Loss Matters

Being unable to smell may seem like a minor nuisance compared to more severe COVID-19 complications. But anosmia can significantly alter daily wellbeing. Smell contributes strongly to our perception of taste. Food becomes bland or metallic without aromatic compounds from spices, herbs, etc activating smell receptors. Poor appetite and weight loss often follow smell impairment.

Anosmia also robs us of environmental cues that most take for granted. Scents influence mental clarity, mood regulation, and staying alert to threats in our surroundings. Loss of these warning signs can jeopardize safety, as with failing to notice a dangerous gas leak or something burning on the stove. Olfaction even plays a key role in immunity and emotional processing. Scent memories tie strongly to limbic system reactions in the brain. With smell loss we lose sentimental connections to comforting or nostalgic smells. The inability to detect noxious odors in spoiled foods or dirty surroundings can also increase disease risk.

Clearly our sense of smell does far more than adding flavor or aroma to life. For COVID long haulers, ongoing loss of smell exacts daily costs and has no quick fix. Understanding the root causes and chances for recovery matter greatly.

Why Does COVID-19 Cause Anosmia?

Strangely enough, the specific reasons why COVID-19 impairs smell remain somewhat mysterious. What we do know is that other respiratory viruses like influenza, rhinovirus, etc can also diminish smell function. Any illness accompanied by sinus congestion and inflammation will muffle airflow carrying aromatic compounds. This tends to cause temporary hyposmia (reduced smell sensitivity) that resolves with the infection.

SARS-CoV-2 differs by triggering moderate to complete smell loss, without sinus blockages, in an estimated 70% of those infected. Unique mechanisms seem to disrupt olfactory signal transduction rather than airflow mechanical issues. Complicating matters is that 93% of people hospitalized for COVID-19 related anosmia had preexisting smell disorders. This hints at a genetic predisposition or immune system vulnerability to post-viral smell damage in certain individuals. However, many people lose all sense of smell for the first time ever after even mild COVID-19 illness.

Research points to possible explanations tied to how this coronavirus infiltrates and replicates inside sustentacular cells that support olfactory neurons. These infected cells release chemokines activating widespread inflammation. Resulting edema (fluid retention in surrounding tissues) may compress olfactory nerve terminals attempting to transmit signals from odor molecule receptors.

Additionally, immune responses recruit killer T-cells targeting and destroying infected sustentacular cells and nearby neuron axons. This combination of mechanical obstruction and damage to smell pathway infrastructure can temporarily shut down signal relay through the olfactory bulb pathways.

In most recovered COVID patients smell returns gradually over weeks or months as inflammation subsides. But let’s look closer at those with persistent anosmia a year or longer after infection.

Can Anosmia Become Permanent After COVID-19?

For around 20% of COVID-19 survivors, smell and taste issues linger without improvement for many months post-recovery. Does this mean their anosmia has become a permanent condition? Not exactly…but possibly for some.

The latest research found 77% of long haulers reporting ongoing “taste” problems actually have persistent phantosmia. This refers to distorted or phantom smells like rancid burning wiring, foul garbage odors, or chemical vapors. Such olfactory hallucinations replaced their normal sense of smell. Only 23% had actual blunting of taste perceptions from smell loss.

What causes this lasting dysfunction where smells remain vividly present yet grossly inaccurate and unwanted? Scientists now confirm phantosmia and parosmia (milder smell distortions) arise from neuroinflammatory damage, likely targeting the olfactory bulb relay in the smell pathway infrastructure.

You see, olfactory receptor neurons have a uniqueness lacking in other nerve cells – lifelong regeneration. These bipolar neurons readily regrow new axons into the olfactory bulb glomeruli when damaged. But surviving axon terminals must rewire correctly into the olfactory bulb smell map to relay accurate information. Under inflammatory duress, miswiring likely jumbles signal relay to/from central smell processing regions – hence vivid hallucinated or distorted phantom smells.

The key implication is that most patients still have intact (though confused and inflamed) olfactory nerve fibers. These neurons attempt to regenerate after immune-mediated injury post-COVID. Their distorted signaling indicates high likelihood the anosmia is temporary rather than permanently destroyed anatomy.

So in most cases, anosmia after COVID seems unlikely to be permanent. Aggressive anti-inflammatory treatments aim to settle inflamed tissues enabling intact olfactory nerves to functionally rewire signaling pathways accurately again. The nerves themselves remain viable if overwhelmed by uncontrolled neuroinflammation.

Still this begs the question – what about that subset of COVID survivors left with no smell perception and seemingly total loss of function? Next we’ll explore factors that may render post-COVID anosmia intractable.

When Can Anosmia Become Permanent After COVID-19?

A 2021 meta-analysis of 24 studies examining long-term smell loss looked closely for discriminating factors between temporary anosmia versus potential lasting damage. Key correlations emerged indicating higher risk for persistent anosmia vulnerable to becoming permanent. These include:

Complete Rather Than Partial Initial Smell Loss

Those unable to detect any aroma signals during acute COVID-19 experienced worse long-term issues. Complete loss implies extensive inflammatory damage overwhelming olfactory structures. The resulting blank slate makes functional recovery less likely as regeneration attempts seem thwarted. Residual partial function better predicts intact neural circuitry remaining viable when inflammation dies down.

Significant Nasal Obstruction Symptoms

While COVID-related smell loss occurs without sinus blockage for most, some studies found combined airflow reduction and anosmia foretells poorer prognosis. Those with preexisting nasal/sinus dysfunction may risk permanent loss when SARS-CoV2 adds insult to existing anatomical vulnerability.

Severe Overall COVID-19 Infection Intensity

Intubated ICU patients progressing to respiratory failure unsurprisingly manifest higher incidence of long-term anosmia. Critical illness equates to extreme immune responses and systemic inflammation exposure. The olfactory bulb network sits in uniquely vulnerable CNS gateway region at risk for collateral damage when cytokines flood the area.

Advanced Age Over 60 Years Old

Like all neurologic functions, olfactory efficiency declines in aging. COVID-19 exacerbates this by accelerating neuronal aging through inflammatory oxidative stress and microvascular injury. Elderly already have fewer olfactory neurons held in precarious regenerative balance. Critical infection pushes the ecosystem past its compensatory limit into potential collapse.

Presence of Parosmia (Smell Distortions)

Remember parosmia indicates surviving neurons misfiring through damaged but intact pathways. This bodes better for recovery odds rather than complete signal failure implying destroyed infrastructure. Those still experiencing phantom smells 6+ months post-COVID recovery may regain accurate signaling eventually versus those with seemingly permanent anosmia.

The harsh reality is COVID-19 presents a unique neurological disorder threatening smell pathway viability. For most afflicted the anosmia should fully resolve or continue improving long-term. But this common issue after COVID-19 could become a lifelong disability for some vulnerable subsets of patients.

Aggressive efforts targeting regaining this vital sensory system matter greatly to those suffering. Let’s survey emerging medical aids that may rehabilitate smell function before it becomes an intractable handicap.

Medical Treatments That Could Restore Smell After COVID-19

Besides basic smell retraining olfactory therapy, several medical options show promise to treat post-COVID smell loss. These aim to control inflammation enabling anatomical recovery while also potentially renewing neuron populations destroyed. Available options include:

Intranasal Corticosteroid Sprays

Localized anti-inflammatory drugs like mometasone (Nasonex), fluticasone (Flonase), or triamcinolone (Nasacort) reduce edema pressing on olfactory nerve terminals. These may enable viable axons to regain signal firing ability once compression resolves.

Oral And Intranasal Antihistamines

Blocking inflammatory histamine receptors (H1 antagonists) reduces associated nasal congestion, mucus production, and swelling effects that can further compress regenerating olfactory nerve axons.

Omega-3 Essential Fatty Acids

Fish oils and algal EPA/DHA supplements work on a cellular level to resolve inflammation contributing to anosmia. Omega-3s also stimulate nerve regrowth factors while limiting oxidative damage.

Intranasal Nerve Growth Factor (NGF)

Recombinant NGF proteins applied inside the nasal passages aim to specifically renew damaged olfactory neurons by activating regenerative support cells. This molecular signaling treatment seeks to regrow viable bipolar neurons from surviving basal stem populations.

Stem Cell Regenerative Therapy

Introducing cultured autologous mesenchymal cells into the nasal cavity may help direct differentiation of new neurons, glia, blood vessels, etc to structurally rebuild damaged olfactory anatomy. Stem cell treatments remain highly experimental but show amazing promise for regenerating lost or dysfunctional neural pathways.

Final Outlook: Complete COVID-Related Anosmia Recovery Is Possible

Smell loss following COVID-19 infection poses complex challenges around regaining this vital sensory ability. The impact on quality of life through distorted flavors, loss of natural warning systems, and sentimental smell memory damage takes daily tolls. Patients desperate for solutions have every right to feel anxious about the possibility of permanent anosmia handicapping them indefinitely.

Yet amid the sobering realities, legitimate reasons for optimism exist too. Unlike blunt force injuries or Toxic environmental exposures that can permanently destroy olfactory anatomy, post-COVID smell dysfunction appears largely tied to RUNEX inflammatory interference with viable cellular structures. These surviving neurons vigorously attempt to regenerate given the chance. Potent anti-inflammatory treatments combined with nerve growth promoters could rehabilitate these cells into renewed functional pathways.

In essence COVID-related anosmia seems unlikely to become firmly permanent in most patients. The plasticity and renewable nature of olfactory bipolar neurons favors eventual signal recovery. But for some subsets with advanced age or extensive infection severity, the damage may overwhelm compensatory mechanisms. These long haulers need prompt aggressive treatment while recovery windows remain open.

With expanded research and advanced smell recovery therapies coming online, we must remain hopeful. Applying biomedical insights into this common neurological complaint can illuminate solutions. In time even some deemed untreatable cases may regain this vital sensory ability and quality of life marker. The science continues progressing at an encouraging pace.

Frequently Asked Questions About Permanent COVID-Related Smell Loss

How common is long-term anosmia after COVID-19?

Approximately 20% of recovered COVID patients report ongoing struggles with smell function lasting months or years after acute infection. 77% of these long haulers suffer parosmia delivering distorted “phantom” smell sensations rather than complete loss. This indicates damaged but partially viable sensory nerve infrastructure. Just 23% describe permanent-seeming loss reflecting destroyed anatomy. These ratios suggest full anosmia recovery remains possible in most patients given proper treatment.

What medical options exist to restore smell after COVID?

Beyond olfactory retraining therapy, current medical interventions to resolve post-COVID anosmia include intranasal corticosteroid sprays, antihistamine medications, omega-3 essential fatty acid supplements, intranasal nerve growth factor proteins, and exploratory stem cell regeneration treatment. These aim to control inflammation, promote nerve regrowth, and potentially regenerate damaged cellular structures along olfactory pathways.

Can young healthy people suffer permanent smell loss after COVID?

Yes, although permanent anosmia risk rises significantly with advanced age and severe infection progressing to respiratory failure, even young otherwise healthy COVID survivors may sustain lasting smell loss. A 2021 meta-analysis found adults under 40 comprise 15% of those with chronic anosmia 6+ months post-recovery. Youth doesn’t confer guaranteed protection against this disabling neurological symptom.

Why do some people recover smell yet others don’t?

Numerous factors affect individual susceptibility to lasting COVID-related smell loss. Those experiencing initial complete rather than partial anosmia struggle more with rehabilitation. Preexisting nasal obstruction or sinus dysfunction may predispose some to permanent deficits. Severe respiratory COVID cases risk greater olfactory bulb inflammation exposure. Advanced age invites regenerative decline. And paradoxically those with parosmia often recover better, indicating partially active neural pathways. Different people simply manifest different anatomical and immunological responses to this virus – with some more vulnerable to lasting sensory damage than others despite similar infection courses.

Can gene therapy or implants restore smell if nerves are destroyed?

Potentially yes – if olfactory bipolar neurons and axon terminals suffered complete destruction, advanced emerging treatments may someday replace these. Gene therapies to induce stem cell differentiation into new neurons are in early developmental phases. So are tiny electronic odorant biosensors with wireless neurostimulator units to replace missing nerve infrastructure. Both these futuristic options are probably at least 5-10 years from clinical availability. But for the newly permanently anosmic, advanced solutions like these may someday help where all else fails.

Key Takeaways: Post-COVID Anosmia And Recovery Expectations

• 20% of recovered COVID patients deal with persistent smell loss lasting months or years – indicating mostly neurological dysfunction rather than permanent destruction after acute infection crisis peaks.
• The majority of long-term cases involve parosmia “phantom smells” implying viable misfiring smell pathways that may still heal and rewire given proper treatment.
• Risk factors for possible permanent anosmia include severe infection, age over 60, prior nasal dysfunction, early complete smell loss, and lack of parosmia. But predictors still only signal probability, not certainty of lasting damage.
• Encouraging emerging medical options like steroids, omega-3s, nerve growth promoters, and experimental stem cell treatments aim to reduce inflammation enabling anatomical olfactory recovery while renewing neuron populations.
• Complete regeneration of smell function post-COVID remains plausible for most patients, though some risk lasting deficits; advanced treatments on the horizon offer greater hope restoring even seemingly permanent loss. Staying vigilant yet optimistic serves sufferers best.

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