Even years after the acute phase of the COVID-19 pandemic faded from daily headlines, one of its most stubborn legacies continues to shadow millions of working adults: post-COVID conditions, the cluster of persistent symptoms now broadly known as long COVID. A new cross-sectional study from Taiwan, published in BMC Psychology, offers a sobering snapshot of what these conditions mean for mental health and the capacity to work, even among people who were highly vaccinated and infected predominantly during the milder Omicron era. The findings challenge a lingering assumption that vaccination and less virulent variants have fully neutralized the long-term occupational and psychological costs of SARS-CoV-2 infection.

The research, led by Jhe-Ping Lin of the Department of Occupational Medicine at Linkou Chang Gung Memorial Hospital in Taoyuan City, together with Chia-Cheng Chang, Chen-Chang Yang, Ting-An Yang and corresponding author Yu-Chung Tsao, set out to answer a question that has become increasingly urgent for occupational health practitioners worldwide: how do employed adults who report persistent post-COVID symptoms differ, in measurable psychological and functional terms, from infected peers who consider themselves fully recovered? Much of the existing long COVID literature emerged from populations infected with earlier viral variants, before widespread vaccination, and focused heavily on physical sequelae. Relatively less is known about the psychological and occupational footprint of post-COVID conditions under contemporary epidemiological conditions, which is precisely the gap the Taiwanese team sought to fill.

The study design was straightforward but methodologically deliberate. Employed adults with prior confirmed SARS-CoV-2 infection were recruited through clinical and occupational-health channels using non-probability sampling, a practical approach for reaching workers with documented infection histories. All participants completed a battery of validated questionnaires assessing four core domains: health-related quality of life, fear of COVID-19, insomnia severity and work ability. The investigators then divided the cohort into two groups based on whether participants reported persistent symptoms consistent with post-COVID conditions, and statistically compared the two groups on every psychological and occupational measure. This symptom-based categorization mirrors the approach increasingly favored internationally, since no single laboratory biomarker can yet reliably define long COVID.

The results were striking in their consistency. Participants reporting post-COVID conditions demonstrated significantly lower quality of life, with a mean difference of 13.9 points on the quality-of-life instrument compared with fully recovered peers. They also scored higher on the Fear of COVID-19 Scale, a validated measure of pandemic-related anxiety, and reported greater insomnia severity, suggesting that disturbed sleep is a common companion of persistent post-viral illness. Perhaps most consequential for employers and policymakers, the post-COVID group showed reduced scores on the Work Ability Index, a well-established instrument that quantifies how well a worker perceives themselves able to meet the physical and mental demands of their job. The mean difference of 3.3 points on this index may sound modest, but in occupational medicine research, shifts of this magnitude on the Work Ability Index are considered clinically meaningful and are associated with elevated risks of reduced productivity, prolonged sickness absence and early exit from the labor force.

To appreciate why these numbers matter, it helps to understand what each instrument measures. Health-related quality-of-life scales capture how illness erodes daily functioning across physical, emotional and social dimensions; a 13.9-point deficit represents a substantial perceived deterioration in wellbeing, not a marginal statistical blip. The Fear of COVID-19 Scale taps illness-related anxiety that can itself become disabling, feeding avoidance behaviors and hypervigilance. Insomnia severity indices quantify difficulties falling asleep, staying asleep and feeling restored by sleep, and chronic insomnia is strongly linked to depression, impaired concentration and workplace accidents. The Work Ability Index synthesizes a worker’s self-assessed physical and mental capacity, diagnosed illnesses and resources relative to job demands, making it one of the most predictive single measures available for future work disability. That all four domains moved in the same negative direction among the post-COVID group paints a coherent picture of a population under compounding psychological and functional strain.

Crucially, these associations emerged within a population that reflects the current reality of the pandemic rather than its early, pre-vaccine chapter. Taiwan maintained exceptionally high vaccination coverage, and the overwhelming majority of infections in the study cohort occurred during the Omicron-dominant period, when the variant itself was generally associated with less severe acute disease. The persistence of measurable psychological and occupational burden under these comparatively favorable conditions suggests that the risk of long-term impairment has been reduced but not eliminated. For the millions of workers globally who have been infected with Omicron-lineage viruses despite vaccination, the Taiwanese data imply that lingering symptoms remain a genuine occupational health concern rather than a relic of earlier pandemic waves.

The authors are careful about what their study can and cannot claim. Because the design is cross-sectional, capturing participants at a single point in time, causal relationships cannot be inferred. It remains possible, for instance, that pre-existing anxiety, poor sleep or low work ability influenced how participants recalled and reported persistent symptoms, rather than the symptoms driving the psychological burden. The non-probability recruitment strategy, while effective for reaching the target population, also limits generalizability; workers who chose to participate in an occupational health study may differ systematically from those who did not. Self-reported symptom status, the standard for long COVID research given the absence of a definitive diagnostic test, introduces additional subjectivity. The researchers openly acknowledge these constraints and call for longitudinal studies to clarify recovery trajectories and functional outcomes over time, which would allow investigators to determine whether reduced work ability precedes, follows or merely co-occurs with post-COVID symptomatology.

Even with those caveats, the study carries practical implications that extend well beyond Taiwan. The authors argue that mental health assessment deserves a central place in post-COVID follow-up care, not as an afterthought but as a routine component of clinical evaluation. This recommendation aligns with a growing body of international evidence linking long COVID to depression, anxiety and sleep disorders, and it reframes post-COVID conditions as a psychosomatic and occupational problem in equal measure with a physical one. For occupational physicians, the message is that a worker presenting with persistent fatigue or brain fog should not only be evaluated for physical sequelae but also screened for insomnia, pandemic-related fear and diminished work capacity. For employers, the findings underscore the value of graded return-to-work programs, workplace accommodations and access to psychological support, since untreated mental health burdens may prolong functional impairment even after physical symptoms begin to subside.

The policy stakes are considerable. Post-COVID conditions affect a substantial fraction of infected individuals worldwide, and because the condition disproportionately impairs the ability to sustain full-time work, its economic ripple effects touch social insurance systems, disability programs and national productivity. Studies conducted in vaccinated, Omicron-era populations are especially valuable for forecasting the forward-looking burden, since they describe the risk profile relevant to new infections rather than historical ones. By demonstrating a 13.9-point quality-of-life deficit and a 3.3-point reduction in work ability under exactly these modern conditions, the Taiwanese study provides quantitative anchors that health economists and policymakers can use to model the ongoing costs of long COVID in the workforce.

The research also highlights the importance of studying long COVID outside the Europe-North America axis, where much of the literature has concentrated. Taiwan’s pandemic trajectory, characterized by early containment followed by a large, late Omicron wave in a highly vaccinated population, offers a distinct natural experiment. The fact that measurable occupational and psychological impairment still emerges in this setting strengthens the argument that post-COVID conditions are a global phenomenon requiring coordinated surveillance, standardized assessment tools and sustained investment in rehabilitation services. The study received no external funding and was approved by the Institutional Review Board of the Chang Gung Medical Foundation, with all participants providing informed consent under protocols compliant with the Declaration of Helsinki.

For now, the study’s central contribution is to quantify, with validated instruments, the invisible toll that persistent post-viral symptoms exact on working adults: poorer perceived health, greater fear, worse sleep and a weakened sense of capacity to meet job demands. As health systems worldwide transition from emergency response to long-term management of COVID-19’s aftermath, evidence of this kind, gathered under the most favorable epidemiological conditions yet seen, serves as a reminder that the pandemic’s occupational and psychological dimensions are far from over. The authors’ call for longitudinal follow-up is the natural next step, and its findings will help determine whether the burdens documented here fade with time or harden into chronic disability for a vulnerable segment of the working population.

After ten years of fieldwork in Taiwan’s remote mountain regions, researchers have identified an 84.1-meter (276-foot) Taiwania fir, now recognized as the tallest tree documented in East Asia. The team also found dense forests containing dozens of giant Taiwania firs, suggesting that other giant trees may remain hidden in Taiwan’s rugged interior.

The study, published in Frontiers in Forests and Global Change, was conducted by a team led by Rebecca Chia-Chun Hsu of the Institute of Taiwan Forestry Research, in collaboration with researchers Chi-Kuei Wang and Chung-Cheng Lee of National Cheng Kung University. Starting in 2014, the group, known as the Taiwan tree seekers, located and measured trees that had previously gone unrecorded by combining traditional field surveys with laser-based mapping and the help of citizen scientists.

The researchers found that the giant trees generally grow at elevations of about 2,087 meters and on slopes with an average inclination of 40 degrees. This combination of elevation and rugged terrain makes conventional tree surveys extremely difficult.

A Decade of Ground-Truthing

In August 2014, a systematic search began when scientists from the Taiwan Forestry Research Institute visited the Cilan conservation area to measure the ‘Chilan Three Sisters’, a group of Taiwania firs known locally but not formally recorded. The tallest tree was 69.3 meters high and had a trunk almost three meters wide. The Tree Project, a group of professional climbers from Australia, photographed the trees in 2017 and helped draw greater attention to Taiwan’s giant forests.

During a subsequent expedition near Mt. Benya and Great Ghost Lake, the team hiked for four days with their equipment to reach the study area. This experience showed how difficult it is to estimate the height of giant trees from the ground, since visual estimates can be unreliable in densely wooded, multi-layered old-growth forests. Although the team measured one tree at 71.7 meters, they concluded that ground-based surveys alone would not be sufficient for such a large and complex landscape.

LiDAR and a Problem With the Landscape

To improve their search, Hsu’s team collaborated with Wang and Lee’s remote sensing group at National Cheng Kung University and adopted LiDAR technology. LiDAR uses laser pulses from aircraft to create three-dimensional models of the forest, including estimates of tree height. However, Taiwan’s rugged topography caused the automated software to misinterpret cliffs and abrupt elevation changes as extremely tall trees.

Human reviewers proved more effective than the automated software at identifying these geological false positives. In 2020, hundreds of citizen scientists began examining the LiDAR profile images manually to distinguish real cases from artifacts. By the end of 2022, the Taiwan Giant Tree Map had identified 941 trees taller than 65 meters.

The researchers concluded that combining airborne laser scanning with crowdsourced image reviews and expert analysis can greatly reduce terrain-related errors in estimating tree heights.

Finding the “Heaven Sword”

In 2023, the mapping project led the team to a candidate for Taiwan’s tallest tree, which could be reached after traveling 20 kilometers down a river and then spending two days climbing. A direct measurement established the tree’s height at 84.1 meters, making it the tallest tree ever documented in Taiwan and East Asia. The team called it the ‘Heaven Sword of the Da’an River’. The Indigenous Rukai people have a name for trees of this kind and describe them as ones that ‘hit the moon’. By early 2026, researchers had documented 10 Taiwania firs taller than 70 meters, including two that exceeded 80 meters.

The mapping effort also brought the team back to the Great Ghost Lake region, nearly ten years after their initial visit. There, they identified about 30 large Taiwania firs growing together in an ancient stand, which the team began calling ‘temples of giants.’ In a hectare of forest near Mt. Benya, they recorded 11 individual trees exceeding 65 meters in height.

What the Giants Are Storing

The importance of these forests goes beyond their height. In 2024, Hsu’s team, in collaboration with 15 citizen scientists, surveyed Tao Tree Valley, home to Taiwan’s third-tallest tree, to determine how much carbon the forest stores. They found a carbon density of 1,384.5 megagrams per hectare, without including the root systems. The estimate is comparable to carbon-storage densities reported for some of the world’s most carbon-rich forests, including giant eucalypt forests in Tasmania. The researchers noted that their estimate did not include root systems and may have underestimated the forest’s true carbon storage.

The researchers still do not know how many other giant trees remain hidden in Taiwan’s mountains. However, the combination of LiDAR mapping, citizen science, and field verification gives them a way to search terrain that would otherwise be nearly impossible to survey systematically.

Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.