6847§ 3.102§ 3.303§ 3.31038 CFR § 4.97, DC 68476847§ 3.102§ 3.303§ 3.31038 CFR § 4.97, DC 68476847§ 3.102§ 3.303§ 3.31038 CFR § 4.97, DC 6847
Nexus letter guide · 6847
Nexus Letter for Sleep Apnea: What It Must Say
The medical opinion connecting Sleep Apnea (6847) to your service is the piece of the file a rater weighs most heavily. This is what that letter has to contain — and a complete, real example you can read before writing a word.
Invented veteran · fictional sample provider · not a signed medical opinion
INDEPENDENT MEDICAL OPINION
Veteran: Samuel Okonkwo (invented veteran — illustrative sample) Condition at issue: Obstructive Sleep Apnea (ICD-10 G47.33) Service-connected condition relied upon: Chronic Sinusitis (ICD-10 J32.9) Basis of claim: Secondary service connection under 38 C.F.R. §§ 3.303, 3.310 Opinion date: August 4, 2026
REASON FOR EVALUATION
This is an independent medical opinion prepared for the purpose of assisting in the determination of eligibility for veterans benefits. Its single question is a medical one: whether Mr. Okonkwo's obstructive sleep apnea is proximately due to, the result of, or aggravated beyond its natural progression by his service-connected chronic sinusitis. It is addressed to the C&P examiner and the VA rating official who will weigh it.
MEDICAL OPINION
It is my opinion that it is at least as likely as not (a 50 percent or greater probability) that Obstructive Sleep Apnea is proximately due to, the result of, or aggravated beyond its natural progression by the veteran's service-connected Chronic sinusitis (38 C.F.R. §§ 3.303, 3.310). In short: but for the veteran's service-connected Chronic sinusitis, Obstructive Sleep Apnea would not have occurred, or would not have progressed to its current severity.
Based on the history and records reviewed and the medical literature governing this condition, I opine that Obstructive Sleep Apnea (ICD-10 G47.33) is proximately due to, the result of, or aggravated by his service-connected Chronic sinusitis (ICD-10 J32.9), under 38 C.F.R. § 3.310. This claim is brought as secondary to Chronic sinusitis, established as service-connected in the veteran's VA claims file; the opinion below rests on that anchor. The mechanism connecting the two conditions — chronic nasal and sinonasal obstruction increasing upper-airway resistance and collapsibility during sleep — is well established in the peer-reviewed literature and applies directly to a claimant, like Mr. Okonkwo, whose sinonasal disease began in service and whose obstructive sleep apnea was later confirmed on polysomnography. My opinion accounts for the recognized non-service risk factors for this condition, none of which displaces the sinonasal pathway as at least an equal and materially contributing cause.
The published example letter — an invented veteran and a fictional sample provider.
Key facts
Rated under
38 CFR § 4.97, DC 6847
Diagnostic code
6847
The standard
“At least as likely as not” — 50% or greater
Connection theories
Direct (§ 3.303) or secondary (§ 3.310) · 3 pathways below
The short answer
A nexus letter for sleep apnea is a medical opinion from a licensed clinician saying your obstructive sleep apnea is "at least as likely as not" (a 50 percent or greater chance) caused by your service, or by a condition VA already rates, such as PTSD, chronic sinusitis or rhinitis, or asthma. To carry weight it has to name the diagnosis confirmed by your sleep study, pick a theory (direct under 38 C.F.R. § 3.303 or secondary under § 3.310), explain the medical reason step by step, and deal with the other causes a rater will think of first, like weight and age. Sleep apnea is not on VA's presumptive lists, so in most claims the nexus opinion is the piece the decision turns on.
What a nexus letter is
A nexus letter is a written medical opinion from a licensed clinician stating that a veteran’s condition is “at least as likely as not” (a 50 percent or greater probability) connected to their military service — or to a condition already service-connected. It is the bridge between a diagnosis and service connection: the VA has your diagnosis and your service records, and the nexus opinion is what ties them together with medical reasoning a rater can weigh.
The standard · 38 CFR § 3.102
“At least as likely as not”
“possibly” · “may be related”Meets the standard
0%50%100%
The opinion does not have to be certain, or even “more likely than not.” A 50 percent or greater probability meets the standard; when the evidence is in approximate balance, the benefit of the doubt goes to the veteran.
What a Sleep Apnea nexus letter must contain
1
The diagnosis, by name and code
Sleep Apnea named as a current, documented diagnosis — the condition the VA rates under 38 CFR § 4.97, DC 6847 (6847). No diagnosis, no service connection: the opinion has to be about a condition that exists in your records.
2
The theory of connection
Direct service connection under 38 C.F.R. § 3.303 (the condition began in or was caused by service), or secondary service connection under § 3.310 (a service-connected condition caused or aggravated it). For Sleep Apnea, the secondary path is common — see the mechanisms below — and the letter must name which theory it is using.
3
The magic words, used correctly
The opinion must be stated to the VA's own standard: "at least as likely as not (a 50 percent or greater probability)." Weaker hedges like "possibly" or "may be related" fail; the standard is a specific legal threshold, and letters that don't invoke it get discounted.
4
A rationale, not a conclusion
The most common fatal flaw is the conclusory letter — an opinion with no reasoning. A rater is instructed to weigh the rationale: what in the records supports the connection, what the medical literature says about the mechanism, and why known alternative causes don't displace it. For Sleep Apnea specifically: Sleep study documenting apnea events + CPAP prescription — requiring a CPAP is, by itself, the 50% level's criterion.
5
A licensed clinician's signature and credentials
The letter is medical evidence only when a licensed clinician — opining within their specialty — reviews it, exercises independent judgment, and signs it with their credentials. VA Claim Commander drafts the letter from your records and your story; your clinician signs it. An unsigned draft is a draft.
What a rater looks for in a Sleep Apnea nexus letter
A diagnosis confirmed by a sleep study
Raters look for a polysomnogram (sleep study) that confirms obstructive sleep apnea. The letter should name it, give the date, and say what it found. A letter about "sleep problems" with no sleep study behind it gives the rater nothing to connect.
One clear theory, not a list of guesses
Direct (it began in service) or secondary (a service-connected condition caused it or made it worse). A letter can argue both, but each one has to be spelled out on its own. A secondary opinion should address both halves of § 3.310: caused by, and aggravated by.
The medical mechanism, in plain steps
For a secondary claim, the letter has to explain how the first condition leads to sleep apnea. For example, blocked nasal passages from chronic sinusitis raise airway resistance and force mouth breathing during sleep, which makes the airway more likely to collapse. A rater weighs the reasoning, not the conclusion.
The other causes, faced head on
Weight, age, and anatomy are the first things a rater will point to. A strong letter names them and explains why they do not displace the service connection. VA does not rate obesity as a disability, but weight gain caused by a service-connected condition can be the middle link in a secondary claim, and the letter can say so when your records show it.
Facts from your file, not a template
Dates, symptoms, and treatment from your own records: when the snoring and daytime sleepiness started, when the sleep study was done, when a CPAP was prescribed. A letter that could be about anyone is easy to set aside.
Direct service connection for Sleep Apnea
Direct service connection under 38 C.F.R. § 3.303 means the sleep apnea began during service. Records rarely say "sleep apnea" in service, because few service members get a sleep study. What a nexus letter can build on instead:
Symptoms in your service records
Snoring, gasping, daytime sleepiness, falling asleep on duty, or fatigue noted at sick call or in a separation exam.
What the people around you saw
Bunkmates and roommates can describe loud snoring and pauses in breathing they witnessed. Under 38 C.F.R. § 3.159(a)(2), a lay person can report what they saw and heard. The clinician can then weigh those accounts in the opinion.
A diagnosis soon after service
A sleep study not long after discharge, with the same symptoms running back to service, lets the clinician tie the two together.
Filing Sleep Apnea as a secondary condition
Under 38 C.F.R. § 3.310, if a service-connected condition caused or aggravated Sleep Apnea, it is service-connected too. The nexus letter’s job becomes explaining the medical mechanism. The pathways veterans most commonly file:
PTSD / Mental HealthSleep Apnea
Sleep Apnea secondary to PTSD / Mental Health
PTSD causes chronic hyperarousal and sleep disturbances that directly damage upper airway muscle tone, dramatically increasing the risk of obstructive sleep apnea.
What proves it: Sleep study (polysomnogram) confirming apnea diagnosis; nexus letter from psychiatrist or sleep specialist linking PTSD hyperarousal to apnea onset.
Chronic airway inflammation from asthma causes upper airway edema and increased airway resistance at night, directly contributing to obstructive sleep apnea.
What proves it: Sleep study confirming apnea; pulmonologist nexus letter describing asthma-related upper airway inflammation as a contributing cause of obstructive sleep apnea.
Sleep Apnea secondary to Chronic Sinusitis / Rhinitis
Chronic sinus and nasal inflammation raises nasal airway resistance — which contributes up to roughly half of total upper-airway resistance — and forces habitual mouth breathing during sleep, displacing the mandible and tongue and reducing pharyngeal diameter. Both mechanisms increase airway collapsibility and worsen obstructive sleep apnea. Nasal obstruction is an independent risk factor for sleep-disordered breathing.
What proves it: Sleep study (polysomnogram) confirming the apnea diagnosis; ENT or sinus imaging documenting the chronic sinusitis/nasal obstruction; nexus letter from ENT, sleep specialist, or treating provider describing elevated nasal resistance and mouth breathing as causes or aggravators of the apnea.
Sleep apnea or insomnia? Tinnitus can make it hard to fall asleep or stay asleep. That is insomnia or a sleep disorder, which is a different claim from obstructive sleep apnea, an airway problem confirmed on a sleep study. If ringing in your ears keeps you awake, the claim to look at is a sleep disorder secondary to tinnitus.
Once Sleep Apnea is service-connected, conditions it causes or makes worse can be claimed under 38 C.F.R. § 3.310. Each one needs its own nexus opinion explaining that link.
Conclusory: an opinion with no rationale. The rater is told to weigh reasoning, and a bare “it’s related” weighs nothing.
Wrong standard: “may be related” or “possibly caused by” instead of “at least as likely as not.”
Ignores the other causes: a strong letter names the recognized non-service risk factors and explains why they don’t displace the service connection.
Outside the specialty: a clinician opining far from their field gets less weight than one whose practice covers the condition.
Unsigned: a draft nobody signed is not medical evidence — it is homework.
Who can write a Sleep Apnea nexus letter
Any licensed clinician qualified to give a medical opinion on Sleep Apnea: a physician, or another licensed clinician opining within their field. VA's test is whether the person is qualified by education, training, or experience (38 C.F.R. § 3.159(a)(1)). It does not have to be a VA doctor. Your own treating provider, who already knows your history, is often the strongest choice.
VA Claim Commander drafts the letter from your records and your own words, so your clinician starts from a complete draft; they review it, change what they disagree with, and sign only if it is their opinion.
If your own doctor won't write one, a licensed clinician through Commander Health can review your records and, only if the evidence supports it, write and sign a nexus letter for Sleep Apnea. It is a flat $500 that includes the records review, separate from any VA Claim Commander plan, and the clinician can decline if your records don't support an opinion.
Do I need a nexus letter for a Sleep Apnea VA claim?
If service connection isn't already established for Sleep Apnea, a medical nexus opinion is usually the piece a rater weighs most heavily. It connects the diagnosis (6847) to your service — or to an already service-connected condition — using the "at least as likely as not" standard. Presumptive claims are the main exception.
What must a nexus letter for Sleep Apnea say?
Four things: the current diagnosis by name and diagnostic code; the connection theory (direct under 38 C.F.R. § 3.303, or secondary under § 3.310); the opinion stated to the "at least as likely as not (50 percent or greater probability)" standard; and a medical rationale grounded in your records and the medical literature — not a bare conclusion. It must be signed by a licensed clinician.
Who has to sign a nexus letter?
A licensed medical professional — a physician, or another clinician opining within their specialty (38 C.F.R. § 3.159(a)(1) asks for someone qualified by education, training, or experience). VA Claim Commander drafts the letter from your own records and story; a licensed clinician reviews, exercises independent judgment, and signs. An unsigned draft is not medical evidence. If your own doctor won't write one, a licensed clinician through Commander Health can review your records and, only if the evidence supports it, write and sign a nexus letter for Sleep Apnea. It is a flat $500 that includes the records review, separate from any VA Claim Commander plan, and the clinician can decline if your records don't support an opinion.
Can Sleep Apnea be claimed secondary to another condition?
Yes — veterans commonly file Sleep Apnea secondary to PTSD / Mental Health, Asthma, Chronic Sinusitis / Rhinitis under 38 C.F.R. § 3.310. In a secondary claim, the nexus letter's job changes: instead of connecting Sleep Apnea to service directly, it explains the medical mechanism by which the service-connected condition caused or aggravated it.
Can sleep apnea be secondary to PTSD?
It can be claimed that way under 38 C.F.R. § 3.310. The nexus letter has to explain the medical link, such as how PTSD's chronic hyperarousal and broken sleep affect the airway, and point to your sleep study and PTSD treatment records. VA decides whether the evidence is enough.
Can sleep apnea be secondary to tinnitus?
That is not a common pathway, and tinnitus does not block the airway. What tinnitus often does is keep people from sleeping: that is insomnia or a sleep disorder, a separate claim that can be filed secondary to tinnitus. If you have both, they are two different conditions with two different letters.
Do I need a sleep study for a sleep apnea claim?
In practice, yes. Raters look for a sleep study (polysomnogram) confirming obstructive sleep apnea before service connection is on the table. If you have never had one, ask your doctor about testing first. The nexus letter comes after the diagnosis.
Is sleep apnea a presumptive condition?
No. Sleep apnea is not on VA's presumptive lists, so most claims need a medical nexus opinion. Some conditions it is often filed secondary to are presumptive for certain veterans under the PACT Act (for example chronic sinusitis, rhinitis, and asthma for qualifying Gulf War and post-9/11 service), which can make the secondary route available.
Does my weight hurt a sleep apnea secondary claim?
Weight is the first alternative cause a rater considers, so the letter has to address it. VA does not rate obesity as a disability, but weight gain caused by a service-connected condition (for example, from medication or pain that limits activity) can be the middle link in a secondary claim when your records show it.
How does VA rate sleep apnea?
Under 38 C.F.R. § 4.97, DC 6847: 0% when documented but without symptoms, 30% for persistent daytime hypersomnolence, 50% when you require a breathing assistance device such as a CPAP machine, and 100% for chronic respiratory failure with carbon dioxide retention or cor pulmonale, or when a tracheostomy is required. The nexus letter decides service connection; the rating is based on these criteria.