Systematic review maps seven years of sports genomics research in Turkish athletes

A systematic review published in Frontiers in Genetics has mapped the full landscape of sports-genomics research involving Turkish athlete populations, identifying 70 eligible reports published between January 2019 and April 2026. The analysis, conducted by Murat Kasap of Bartın University and Erkut Tutkun of Bursa Uludağ University, reveals a field dominated by candidate-gene association studies, with genome-wide approaches only beginning to appear. Behind the headline numbers lies a more nuanced picture: those 70 reports trace back to just 58 operationally unique study populations, because several groups of researchers published multiple papers drawing on the same cohorts of athletes and controls.

The scale of the underlying evidence base is modest but real. After merging confirmed shared cohorts, the 58 unique populations comprised 3,201 athletes and 3,683 non-athlete controls, a total of 6,884 participants. The authors emphasise that these figures should not be read as a simple sum of sample sizes across all published articles, since some participants contributed data to more than one report. Six confirmed shared-cohort clusters accounted for 18 of the 70 reports, or 25.7 percent, a finding with direct consequences for how the literature’s apparent breadth should be interpreted.

The review followed the PRISMA 2020 reporting standard, with a protocol registered prospectively on the Open Science Framework. The search spanned seven sources: Web of Science Core Collection, Scopus, PubMed/MEDLINE, SPORTDiscus with Full Text, Google Scholar, and the Turkish databases TRDizin and DergiPark. Scopus contributed the largest share of the 1,740 records identified, with 882, followed by Web of Science with 324 and PubMed with 225. After removal of 717 duplicates, 1,023 unique records underwent title and abstract screening, 627 were excluded at that stage, and 396 full texts were assessed. Of these, 335 failed to meet the eligibility criteria, leaving 61 database-derived reports, to which nine more were added through backward reference-list checking and forward citation searching.

Eligibility was defined at the level of the study population rather than authorship. Turkish authorship or institutional affiliation alone did not qualify a paper; instead, studies had to include athletes recruited in Türkiye, Turkish national or club-level athlete populations, or separately extractable Turkish athlete subgroups within multinational studies. The exposure of interest was inherited genetic or genomic variation, ranging from single-nucleotide variants and insertion/deletion polymorphisms to genome-wide markers and aggregated genomic profiles, examined in relation to sport participation, performance, physiological or metabolic traits, injury susceptibility, or sport-related psychological characteristics.

The methodological profile of the field is strikingly lopsided. Candidate-gene association studies accounted for 64 of the 70 reports, or 91.4 percent. Only three reports, 4.3 percent, used genome-wide association study designs, one used an exome-wide approach, one applied exome data in a candidate-gene analysis, and one evaluated a targeted inherited insertion/deletion variant. This distribution matters because athletic performance is widely understood to be a polygenic trait, shaped by many variants of small effect rather than a handful of influential genes. Genome-wide and exome-wide strategies can reduce reliance on a small set of repeatedly selected variants, but they demand large, well-characterised samples, harmonised phenotype definitions, ancestry-aware analyses, strict control of multiple testing, and independent replication.

The authors are careful not to argue that genome-scale methods should simply replace candidate-gene work. Their conclusion is that the limited number of genome-scale reports does not establish a sustained transition away from candidate-gene research, and that future studies should choose an approach proportionate to their question and sample size. Candidate variants in genes such as ACTN3, ACE, PPARA, and COL5A1 have been examined frequently in sport populations worldwide, yet many reported associations have not been consistently replicated across populations or sporting contexts, a caveat the review carries into its assessment of the Turkish literature.

Thematically, the literature splits almost evenly between two dominant concerns. Twenty-eight reports, 40 percent each, focused primarily on athletic performance or a performance-related phenotype, and on athlete status, sport participation, or genotype distribution. The remaining themes were far less common: five reports addressed sport-related psychological traits, five addressed injury susceptibility, and four addressed physiological, metabolic, or anthropometric traits. Each report was assigned one primary theme for counting purposes, so studies reporting multiple outcomes were not counted repeatedly. The authors note that these descriptive categories do not imply the evidence is equally mature or equally credible across themes.

The sports represented reveal both breadth and fragmentation. Football was the most frequently studied single sport, with 14 unique populations and 652 athletes. Nine populations, totalling 1,256 athletes, were classified as multi-sport or not reliably separable by sport, because the underlying reports described mixed athlete samples without extractable sport-specific participant distributions. Volleyball, wrestling, cross-country skiing, running, bodybuilding, basketball, and arm wrestling also appeared, alongside smaller cohorts ranging from triathletes and ice hockey players to ultimate frisbee athletes and even competitors in HADO, an augmented-reality sport. The authors caution that a genotype associated with athlete status in one sport cannot be assumed to show the same association with an endurance phenotype, an injury outcome, or a psychological trait in another.

The review’s treatment of cohort overlap is one of its most methodologically significant contributions. Reports were considered to arise from a confirmed shared cohort only when evidence such as author overlap, recruitment setting, sport, recruitment period, sample size, demographics, and reported genetic and phenotypic information supported that conclusion. Retaining non-overlapping reports from the same cohort preserved useful information, but treating them as fully independent would have exaggerated the size of the underlying participant base. The authors call on future researchers to report cohort provenance, recruitment sites and periods, participant overlap, and reuse of comparator samples more clearly to facilitate synthesis.

Several limitations temper the findings. Embase could not be searched because institutional access was unavailable, and Google Scholar’s dynamic search interface is not fully reproducible, so retrieval completeness may have been affected; the reviewers captured and screened the first 200 Google Scholar results in line with published guidance. The heterogeneity of the included literature precluded a meta-analysis of individual variant effects, and formal tests for publication bias were not performed, though the authors considered such bias qualitatively. Cohort overlap also could not be excluded where reports lacked sufficient detail. The review’s broader message is a call for transparency: prospectively defined phenotypes, preregistered genetic models, adequate sample-size planning, complete reporting of quality control and multiple-testing procedures, ancestry-aware analysis, and multicentre collaboration to enable independent replication. Individual association findings, the authors conclude, warrant cautious interpretation, particularly where samples are small, replication is absent, and analytical decisions are unclear.

Subject of Research: A systematic review of sports genomics studies in Turkish athlete populations published from 2019 to 2026

Article Title: Sports genomics research in Turkish athlete populations 2019 to 2026: a systematic review

Article References: Kasap, M., & Tutkun, E. (2026). Sports genomics research in Turkish athlete populations 2019 to 2026: a systematic review. Frontiers in Genetics, 17, Article 1921682. https://doi.org/10.3389/fgene.2026.1921682

Image Credits: AI Generated

DOI: 10.3389/fgene.2026.1921682

Keywords: sports genomics, Turkish athletes, systematic review, candidate-gene studies, GWAS, ACTN3, ACE, athletic performance, PRISMA, cohort overlap, genetic polymorphisms, football