The 100 Most-Cited Websites in Perplexity for High-Stakes Health and Medical Consumer Decisions

LLM Authority Index Research | Perplexity | Health and Medical | July-September 2026

Perplexity uses a distinct source ecosystem when consumers ask high-stakes questions about hearing aids, online doctors, online pharmacies, online therapy, medical alert systems, fertility and IVF clinics, addiction treatment, mental health treatment, assisted living, home health care, dental implants, STD tests, and weight-loss or metabolic-health services.

Across 858 deduplicated Perplexity responses covering 14 health and medical source verticals, Healthline ranked #1, appearing as a cited domain in 12.82% of eligible responses. SeniorLiving.org ranked #2 at 8.97%, the National Council on Aging at 8.86%, HelpGuide.org at 7.34%, and GoodRx at 5.24%. HearingTracker tied GoodRx on response coverage at 5.24% and ranked #6 after the citation-event tie-break.

The category source market has a different shape from Perplexity overall. The Top 10 account for only 27.5% of health domain-response appearances, below Perplexity overall at 35.0%, but the health Top 100 still account for 66.0%, close to the broader platform's 66.9%. The result is a relatively diffuse head with a long but still strategically meaningful Top 100.

Only 32 of the health and medical Top 100 domains also appear in Perplexity's overall Top 100, a 19.0% Jaccard similarity. That is a strong category effect: a broad Perplexity source leaderboard misses many health publishers, medical information sites, provider-owned sites, senior-care resources and specialty sources that become important once the prompt population is restricted to high-stakes health decisions.

The source-capture audit also matters. The raw deduplicated health slice contained 2,367 citation-array entries before public-source filtering. We excluded 218 obvious technical or unusable entries, including 171 Perplexity thumbnail CDN URLs, 33 st.perplexity.ai static assets, 13 Mapbox homepage/infrastructure entries and one blank citation URL. The public ranking therefore uses 2,149 substantive citation events.

Answer Capsule

In a July-September 2026 analysis of 858 deduplicated Perplexity responses across 14 high-stakes health and medical source verticals, Healthline was the most frequently cited registrable domain, appearing in 110 responses, or 12.82% of the measured panel. SeniorLiving.org followed at 8.97%, NCOA.org at 8.86%, HelpGuide.org at 7.34%, and GoodRx at 5.24%. After technical-source filtering, the study counted 2,149 substantive citation events, 1,981 domain-response appearances, and 556 cited registrable domains. Only 32 domains overlapped with Perplexity's broader Top 100, showing that the health source market is highly category-specific.

Key Findings

• Healthline leads Perplexity health citations: 110 responses and 12.82% response citation coverage.
• Senior and aging sources are unusually prominent: SeniorLiving.org ranks #2 and NCOA.org #3, reflecting strong citation visibility in hearing aids, medical alert systems, assisted living and related senior-decision prompts.
• Health specialists materially over-index: NCOA.org has about 6.6x its Perplexity-wide coverage inside this health slice, HelpGuide.org about 6.6x, GoodRx about 6.6x, HearingTracker about 6.6x, and Medical News Today about 5.2x.
• Broad platform rank is not enough: only 32 of the health Top 100 also appear in Perplexity's overall Top 100.
• The category head is less concentrated than Perplexity overall: Top 10 health sources account for 27.5% of response-level source appearances versus 35.0% for Perplexity overall.
• The Top 100 still capture most of the measured source activity: 66.0% of health domain-response appearances are in the category Top 100.
• Vertical leaders are highly specialized: HearingTracker and NCOA lead hearing-aid prompts; SeniorLiving.org and NCOA lead medical-alert prompts; GoodRx and Amazon rise in online pharmacy prompts; CCRM IVF leads both fertility and IVF source views; provider and specialist sites lead several treatment-oriented verticals.
• Monthly drift is meaningful: only 35 domains remained in the monthly Top 100 in July, August and September.
• Reddit weakened sharply within this health slice: it ranked #4 in July, #5 in August and #41 in September.
• Healthline remained the strongest recurring source: #1 in July, #3 in August and #1 in September.

Questions This Study Answers

• Which websites dominate Perplexity citations for high-stakes Health and Medical decisions, and how does that source hierarchy change by vertical?
• How persistent is Perplexity's Health and Medical source market over time, and how portable is that visibility to other AI platforms?
• What should health publishers, provider brands, healthcare marketers and CMOs measure before allocating resources to Perplexity-focused content, PR, partnerships or earned media?

Why This Research Belongs in Daily AI Search Marketing Decisions

Article 40 sits at the intersection of two commercially useful views of the same source market:

• the Perplexity platform view, which asks which sources recur across high-stakes consumer decisions on Perplexity; and
• the Health and Medical decision-family view, which asks which sources recur across six AI platform families for one high-stakes category.

For publishers and specialist health sites, that intersection supports a more precise claim than saying a domain is simply "visible in Perplexity." A source can document whether it is cited specifically for health and medical consumer decisions, whether that visibility persists over time, and whether its source presence is broad across multiple health verticals or concentrated in one specialist decision journey.

For healthcare brands, providers, medical-device companies, senior-care businesses, CMOs, PR teams and agencies, the operating question is:

Which sources are already present around the exact health decisions our customers ask Perplexity to help them make?

Six findings matter for daily planning:

• the Top 100 account for 66.0% of domain-response appearances in this Perplexity Health and Medical slice;
• the Top 10 account for only 27.5%, meaning the source head is relatively diffuse;
• only 32 domains overlap between this Health and Medical Top 100 and Perplexity's broader High-Stakes Top 100, a 19.0% Jaccard similarity;
• 35 domains remained in the monthly Health and Medical Top 100 in July, August and September, and the median of the three monthly Top 100 Jaccard comparisons was 29.0%;
• the final child-study Top 100 lists show Perplexity sharing 50 domains with Google AI Overviews, 49 with Google AI Mode, 46 with Gemini, 44 with ChatGPT and 38 with Microsoft Copilot; and
• 218 technical or unusable citation entries were excluded before constructing the public source leaderboard.

The parent Health and Medical Citation Authority Study provides the category-level Persistence-Portability Gap interpretation. It reports:

• 61.3% median monthly Top 100 persistence;
• 25.8% median cross-platform Top 100 portability; and
• an approximate 35.5 percentage-point Persistence-Portability Gap.

Article 40 answers a narrower Perplexity-specific question. Its 29.0% median monthly Top 100 persistence should not be subtracted from one pairwise cross-platform overlap to create a Perplexity-specific gap. The parent PPG uses category-level summary statistics across the broader family.

The parent family is also unusually fragmented across engines. The final six Health and Medical platform studies contain 290 distinct Top 100 domains in their combined union. Only 20 domains appear in all six platform Top 100 lists, while 161 appear in only one.

The concentration result should not be confused with stability or portability. Perplexity Health has a relatively diffuse head, a manageable Top 100, substantial month-to-month rotation, and a source portfolio that transfers imperfectly to other AI platforms. Those are different measurements.

Citation visibility should remain separate from brand mentions, recommendation rate, ranking, sentiment, citation-recommendation coupling, clinical quality, treatment safety and downstream business outcomes. A source can be frequently cited without causing Perplexity to recommend a specific provider, product, clinic or treatment, and citation frequency does not validate medical advice.

Commercial Action Matrix: What Publishers and CMOs Can Do With the Findings

The daily operating model is therefore four-layered:

1. Current Perplexity Health core: maintain the sources that matter now, with the collection date attached.
2. Vertical and prompt-cluster layer: identify which sources dominate the exact hearing-aid, medical-alert, pharmacy, online-doctor, fertility, addiction-treatment, dental, therapy or other health decision.
3. Longitudinal check: monitor whether priority sources persist, decline, rotate or change rank.
4. Cross-platform check: determine whether the same sources also matter in Google AI Overviews, Google AI Mode, ChatGPT, Gemini and Microsoft Copilot.

How This Study Fits the High-Stakes Consumer Decisions Research Corpus

Article 40 is the intersection of two parent studies:

• The Perplexity Platform Study
• The Health and Medical Citation Authority Study

It should also be read with:

• the 2026 AI Citation Authority Study;
• the Persistence-Portability Gap;
• Do AI Platforms Cite the Same Websites?;
• How Stable Are AI Citations?;
• Reddit's Decline in AI Citations for Health and Medical Decisions; and
• How Reddit Citations Changed in Perplexity for Health and Medical Decisions.

Articles 24, 25, 26, 41 and 42 provide the same Health and Medical decision-family cut for Google AI Overviews, Google AI Mode, ChatGPT, Gemini and Microsoft Copilot.

What We Studied

This study isolates Perplexity responses associated with the Health and Medical family of the frozen LLM Authority Index High-Stakes Consumer Decisions corpus.

The family contains 14 preserved source vertical labels:

1. Addiction Treatment Centers
2. Assisted Living Facilities
3. Dental Implants
4. Fertility Clinics
5. Hearing Aids
6. Home Health Care
7. IVF Clinics
8. Medical Alert Systems
9. Mental Health Treatment Centers
10. Online Doctors
11. Online Pharmacies
12. Online Therapy
13. STD Tests
14. Weight Loss and Metabolic Health

Study size

Responses by month

Medical Alert Systems has no July source file because that dataset was not produced in July. Missing months are treated as unavailable rather than as zero-citation observations.

The primary metric is Response Citation Coverage: the percentage of eligible Perplexity health responses that cited a domain at least once. A domain counts no more than once in a response for the primary metric even when multiple pages from the same site are cited.

This section answers

• What denominator and primary metric does this Perplexity Health and Medical ranking use?
• Which 14 health and medical source verticals are represented, and how are missing months or extraction failures handled?
• Why were Perplexity thumbnail, static-asset and map entries removed, and why are response coverage and citation-event counts reported separately?

The Top 25 Perplexity Health and Medical Citation Sources

The first 25 positions mix broad consumer-health publishers, senior-care resources, pharmacy and telehealth sources, mainstream media, product-review sites and specialist medical-information publishers. This is not a quality ranking. It measures how often a domain appeared as a visible cited source in the measured prompt panel.

The Full Top 100 Perplexity Health and Medical Citation Sources

The long tail matters. A domain can rank modestly across the full health category and still dominate a specific consumer-decision vertical.

Citation Concentration

Perplexity's health source distribution has a less concentrated head than Perplexity overall, while the full Top 100 capture a similar share of the source market.

The Top 10 account for 27.5% of response-level domain appearances, compared with 35.0% for Perplexity overall. By the Top 100, the gap nearly disappears: 66.0% of health appearances versus 66.9% overall.

For brands and publishers, this means the practical health source market cannot be reduced to five or ten publishers. The first page of a leaderboard matters, but specialist sites remain strategically important deeper in the list.

Health and Medical Specialization vs. Perplexity Overall

Only 32 of the Perplexity health Top 100 also appear in Perplexity's overall Top 100. The resulting Jaccard similarity is 19.0%.

The table below compares the leading health sources with their broader Perplexity coverage. A lift above 1.0x means the domain appears more frequently in this health slice than across the full Perplexity High-Stakes Consumer Decisions panel.

Several patterns stand out:

• Healthline rises from #11 overall to #1 in health and reaches about 4.8x its broader Perplexity coverage.
• NCOA.org, HelpGuide.org, GoodRx and HearingTracker each reach roughly 6.6x their broader platform coverage in this health slice.
• Amazon is only #44 in Perplexity overall but #9 in the health category, driven largely by online-pharmacy and adjacent commerce prompts.
• Forbes and Reddit remain visible, but both are less concentrated in the health slice than across Perplexity overall.
• Medical News Today, Verywell Mind, Everyday Health, SafeHome and TheSeniorList become much more important inside the category than a platform-wide ranking would suggest. The strategic conclusion is that broad Perplexity authority and health-specific source importance are not interchangeable.

The Most-Cited Sources by Individual Health and Medical Vertical

The vertical table changes the interpretation of the category leaderboard:

• Hearing Aids is led by NCOA.org, HearingTracker and SeniorLiving.org.
• Medical Alert Systems is led by SeniorLiving.org, NCOA.org and SafeHome.org.
• Online Doctors is led by Healthline, GoodRx and Doctor on Demand.
• Online Pharmacies is led by GoodRx, Amazon and Walgreens.
• Online Therapy is led by Healthline, HelpGuide and Verywell Mind.
• STD Tests is led by Healthline and Medical News Today.
• Fertility Clinics and IVF Clinics are led by CCRM IVF, with other specialist or data sources behind it after infrastructure URLs are removed.
• Mental Health Treatment Centers is led by Medscape, U.S. News and McLean Hospital.
• Addiction Treatment Centers is led by American Addiction Centers in this measured slice.

A category Top 100 should therefore be treated as a source map, not a universal outreach list and not a clinical-quality scorecard.

Breadth vs. Specialization

Broad citation visibility and specialist visibility are different assets.

Reddit appears across seven preserved health source verticals even though it ranks #11 category-wide. Everyday Health appears across six. Healthline, HelpGuide, Forbes and Medical News Today each appear across five. Those sources provide category breadth.

Specialists can be far more important to a particular buyer journey. HearingTracker appears in only one preserved vertical but ties GoodRx at 5.24% category-wide response coverage because its Hearing Aids presence is so strong. SafeHome is similarly concentrated in Medical Alert Systems. CCRM IVF becomes a leading source in both fertility-clinic views despite not appearing near the category-wide Top 25.

For a CMO, the useful question is not simply, "Which health publisher ranks highest?" It is, "Which recurring sources surround the exact consumer-health prompts that matter to this service on this platform?"

Monthly Persistence and Citation Drift

Perplexity's health Top 100 had a recognizable core but substantial perimeter movement across the three-month study window.

Only 35 domains appeared in the monthly Top 100 in all three months. The median of the three monthly Top 100 Jaccard comparisons was 29.0%.

The head was more stable than the tail:

• Healthline ranked #1 in July, #3 in August and #1 in September.
• SeniorLiving.org ranked #8, #1 and #3.
• NCOA.org ranked #3, #2 and #4.
• HelpGuide.org climbed from #22 in July to #8 in August and #2 in September.
• GoodRx moved from #2 to #7 to #24.
• Reddit moved from #4 to #5 to #41, a much sharper decline than the leading health-specialist sources.

The July-August Top 100 shared 57 domains. July-September shared 45. August-September shared 41. That level of movement means a static annual publisher list can become stale quickly even if a few category leaders remain persistent.

Platform Differences: Perplexity's Health and Medical Source Market Is Not Interchangeable With Other AI Engines

The final Health and Medical child-study Top 100 lists show meaningful cross-platform overlap, but no other measured engine uses the same source portfolio.

Perplexity is closest to the two Google AI search surfaces in this decision family. Gemini and ChatGPT are somewhat farther away, while Microsoft Copilot is the least similar sibling Top 100.

That difference is commercially important. A source strategy optimized for Google AI search, ChatGPT, Gemini or Copilot is not automatically a Perplexity health-source strategy.

The parent Health study reports only 20 domains present in all six platform Top 100s, while 161 domains appear in only one platform's Top 100. That is a strong signal that healthcare source planning should preserve both a cross-platform core and engine-specific specialist layers.

The operating implication is to maintain three layers: a cross-platform Health and Medical core, a Perplexity-specific source layer, and a vertical-specific specialist layer.

This section answers

• Do the same publishers and health sources lead every AI platform?
• Which engines share the most Perplexity Health and Medical sources?
• Should a healthcare brand use one universal outreach list for all AI platforms?

Prior Research and Why the Rankings Can Look Different

Ahrefs: broad U.S. all-topic Perplexity queries

Ahrefs' September 2026 Perplexity study tracks more than 3.1 million U.S. queries across all topics. Reddit ranks #1 at 21.6% mention share, YouTube #2 at 20.8%, Wikipedia #3 at 6.3%, and Healthline #6 at 2.6%. WebMD ranks #13 at 1.3%, PMC #19 at 1.1%, and Medical News Today #20 at 1.0%. Ahrefs: The 50 Most-Cited Websites in Perplexity

That is very different from Article 40, where Healthline leads at 12.82% response citation coverage, followed by SeniorLiving.org, NCOA and HelpGuide.

The difference is not a contradiction. Ahrefs measures broad all-topic mention share among its leading sources, while Article 40 measures response-level domain presence inside a fixed high-stakes Health and Medical decision panel.

Machine Relations: Consumer Health leaders change with question shape

Machine Relations' September 23, 2026 Index release covers 23,280 cited domains, 129,264 citation events and 16,475 observed answer runs across six engines and 93 published category-question segments. In its Consumer Health category, Healthline leads the best-tools question shape at 43.2%, while UCLA Health leads the is-it-worth-it shape at 37.7%. Machine Relations Index Report, September 23, 2026

Its Healthcare Services category is different again: OmniMD leads best-tools at 32.7%, NIH leads is-it-worth-it at 26.2%, and NIH leads the combined Healthcare Services category at 17.7% across 1,144 runs.

Machine Relations uses a multi-engine system, a different category taxonomy and question-shape framework, and different denominators. Those figures should not be merged with Article 40. The useful agreement is methodological: health source leadership changes with the decision type and measurement contract.

Tinuiti: Perplexity is a notable exception in broader social-source trends

Tinuiti's Q3 2026 AI Citation Trends Report tracks ChatGPT, Perplexity, Google AI Mode, Google AI Overviews, Gemini and Microsoft Copilot across commercial categories including OTC health. It reports that most tracked AI platforms are at or near Q3 highs in social citation share, with Perplexity a notable exception. Tinuiti Q3 2026 AI Citation Trends Report

That direction is consistent with Article 40's sharp Reddit movement from #4 in July to #41 in September, although the categories, prompt sets and metrics differ and the percentages should not be merged.

Studies can disagree because of:

• query selection
• health vertical mix
• commercial intent
• geography
• time window
• ranking metric
• citation-event versus response-level counting
• source-type classification
• technical-asset exclusions
• domain normalization
• platform mode and retrieval behavior

The relevant question is not which ranking is universally correct. It is which ranking matches the health decision environment and measurement contract a publisher, provider or brand actually cares about.

Why This Study Is Different

This article combines several features that are often separated in AI citation research:

• a high-stakes consumer health decision prompt population;
• 14 preserved health and medical source vertical labels;
• a three-month July-September 2026 observation window;
• 858 deduplicated Perplexity responses;
• response-level domain coverage as the primary metric;
• separate raw citation-event counts;
• Public Suffix List domain normalization;
• explicit Perplexity thumbnail, static-asset, map and blank-URL exclusions;
• monthly Top 100 persistence analysis;
• comparison with Perplexity's broader source market; and
• individual vertical source views showing both broad publishers and narrow specialists.

The study is designed to answer a commercial source-visibility question, not a medical-quality question. A citation does not certify clinical accuracy, safety, efficacy or regulatory compliance.

Why AI Citation Studies Can Disagree

Two Perplexity citation studies can both be methodologically sound and still produce very different rankings because of differences in:

• all-topic versus health-specific prompt populations;
• informational versus buyer-intent, comparative, provider-selection or treatment-search prompts;
• consumer Perplexity interface, API or another surface;
• geography and language;
• model and retrieval version;
• observation date;
• URL-level versus registrable-domain normalization;
• whether multiple URLs from the same domain count once or multiple times;
• treatment of platform static assets, thumbnails, map infrastructure and blank URLs;
• handling of zero-citation responses and extraction failures;
• treatment of overlapping source datasets;
• response-level coverage versus raw citation-event share; and
• whether the study uses a fixed panel, a continuously sampled panel or an external keyword universe.

A citation percentage should always be read together with its denominator and collection contract.

What This Means for Health and Medical Publishers

Publishers can use citation data to document where their content is appearing in AI-supported consumer research, but claims should stay observational.

A health publisher can responsibly document:

• its response-level citation coverage;
• the health verticals in which it appears;
• whether it is a broad category source or a narrow specialist source;
• its monthly persistence;
• the AI platforms that cite it; and
• the exact commercial decision contexts where it becomes visible.

A defensible publisher statement is:

Our domain is measurably present among the visible sources Perplexity cites when consumers research specific high-stakes health decisions in this measured panel.

A publisher should not translate that into a claim that its content is clinically endorsed by Perplexity, that citations prove medical accuracy, or that paid placement will cause AI systems to recommend a treatment or provider.

What This Means for Brands and CMOs

For health, senior-care and medical-service brands, a useful earned-media source map has at least three layers.

Broad consumer-health publishers

Healthline, Medical News Today, Everyday Health, Forbes and similar sources can create broad visibility across multiple health topics.

Senior and decision-support authorities

SeniorLiving.org, NCOA.org, SafeHome and TheSeniorList become disproportionately important in hearing aids, medical alert systems, assisted living and adjacent aging-related decisions.

Product, provider and specialty sources

GoodRx, HearingTracker, Doctor on Demand, CCRM IVF, American Addiction Centers, McLean Hospital, Labcorp and other specialists can become more important than a broad publisher inside one buyer journey.

The source map should therefore be matched to the brand's actual prompt clusters. A telehealth company should not use the same publisher priority list as a hearing-aid company merely because both sit inside the same broad health family.

Brands should also distinguish citation visibility from recommendation visibility. A domain can be heavily cited without its associated company being recommended, and a company can be recommended using third-party sources rather than its own site.

Methodology

Research source

This study uses the frozen July-September 2026 LLM Authority Index High-Stakes Consumer Decisions archive used by the parent citation-authority study and the other platform/category articles in this research program.

Platform filter

Only observations assigned to the Perplexity platform family are included.

Category assignment

Observations are included when their preserved source memberships belong to the Health and Medical family. The 14 source labels are listed in the What We Studied section.

Exact file deduplication

Byte-identical source files were deduplicated by SHA-256 before observation processing.

Analytical anti-double-counting

Within the category-platform slice, observations were treated as exact repeats when they shared the same:

• report month;
• exact raw platform/source surface;
• normalized prompt text; and
• exact set of original citation URLs.

One analytical record was retained while preserving originating source memberships. This is an anti-double-counting rule, not proof that Perplexity executed a prompt only once upstream.

Prompt normalization

Prompt matching uses Unicode NFKC normalization, case folding, whitespace collapse and trimming. Prompt wording is otherwise preserved.

Explicit extraction failures

No Perplexity health observation in this slice was explicitly marked as an extraction failure.

Domain normalization

Citation URLs were parsed to hostnames, normalized to lowercase, stripped of leading www., and consolidated to registrable domains using Public Suffix List logic.

Perplexity-specific infrastructure exclusions

The deduplicated health slice contained 2,367 captured citation entries before public-source filtering. The public publisher ranking excludes 218 technical or unusable entries:

• 171 thumbnail CDN URLs on d2u1z1lopyfwlx.cloudfront.net;
• 33 static-asset URLs on st.perplexity.ai;
• 13 Mapbox homepage/infrastructure entries associated with map outputs; and
• 1 blank or unusable citation entry.

These exclusions are based on the function of the surfaced URL. Substantive platform-owned or map-related pages are not automatically excluded merely because of ownership.

Primary metric

Response Citation Coverage = eligible Perplexity health responses citing domain d at least once / all eligible Perplexity health responses.

The denominator for this article is 858 responses. A domain counts no more than once per response for this metric.

Secondary metric

Citation events count individual substantive citation entries after public-source filtering. A response can contain multiple citation events from one domain even though that domain counts once for response coverage.

Monthly ranks

July, August and September Top 100 lists are calculated independently from eligible responses in each month using the same public-source rules.

Vertical views

A deduplicated response can retain more than one originating source membership when overlapping exports contain the same exact observation. Vertical tables are descriptive source views and are not assumed to be statistically independent.

Missing July data

Medical Alert Systems has no July source file because that dataset was not produced in July. Missing months are treated as unavailable rather than as zeros.

No causal interpretation

A visible citation establishes an observed source relationship. It does not prove that a citation caused Perplexity to mention, recommend or rank a company, and it does not validate medical advice, clinical quality or treatment safety.

Limitations

This study should be interpreted within its measured scope.

• It is a commercial high-stakes consumer decision panel, not a random sample of all health information seeking.
• Source vertical labels are preserved dataset memberships and can contain overlapping prompts.
• Exact-repeat handling reduces double counting but cannot reconstruct upstream execution logs that were not included in the archive.
• Citation presence does not measure whether a source was read first, weighted most heavily or causally responsible for an answer.
• Response Citation Coverage does not measure traffic, impressions, conversions or recommendation rate.
• Registrable-domain normalization intentionally collapses subdomains and can hide page-level differences.
• The three-month window captures July through September 2026 and should not be assumed to describe future Perplexity behavior.
• Medical Alert Systems lacks July data because no July file was produced.
• Some vertical slices are small. Dental Implants, for example, has only six eligible Perplexity responses in the frozen child-study slice, so vertical percentages there should be treated as descriptive rather than stable market estimates.
• This is not a medical-quality evaluation. Highly cited sources can still contain content that is incomplete, outdated or inappropriate for an individual patient.

Commercial Disclosure

LLM Authority Index publishes independent citation research designed to measure which sources appear across AI systems and commercial query categories. Related LLM Authority Index, CiteWorks Studio and affiliated properties may provide commercial AI-search measurement, research or optimization services.

Commercial relationships do not change the frozen source corpus, ranking metric, domain-normalization rules, technical-source exclusions or result tables used in this article. Advertising, sponsorship or service relationships should not be interpreted as an ability to purchase a ranking, citation or recommendation in this research.

References

1. LLM Authority Index: 2026 AI Citation Authority Study
2. LLM Authority Index: Most-Cited Websites in AI for Health and Medical Decisions
3. LLM Authority Index: Perplexity Platform Top 100
4. LLM Authority Index: Persistence-Portability Gap
5. Ahrefs: The 50 Most-Cited Websites in Perplexity, September 2026
6. Machine Relations: Index Report, September 23, 2026
7. Tinuiti: Q3 2026 AI Citation Trends Report

Related LLM Authority Index Research

Parent studies and measurement framework

• 2026 AI Citation Authority Study
• Health and Medical Citation Authority Study
• Perplexity Platform Study
• Persistence-Portability Gap
• Do AI Platforms Cite the Same Websites?
• How Stable Are AI Citations?

Sibling Health and Medical platform studies

• Google AI Overviews
• Google AI Mode
• ChatGPT
• Gemini
• Microsoft Copilot

Reddit trend studies for this category

• Health and Medical Reddit parent study
• Google AI Overviews Reddit trend
• Google AI Mode Reddit trend
• ChatGPT Reddit trend
• Perplexity Reddit trend
• Gemini Reddit trend
• Microsoft Copilot Reddit trend

Article 40 is the Perplexity x Health and Medical intersection study. The parent articles explain the broader platform and decision-family markets. The sibling platform studies show portability across engines. The Reddit studies provide one longitudinal source example inside the same Health and Medical decision family.