Barriers and enablers to physical activity in people with venous leg ulcers: a systematic review of qualitative studies
Abstract
Background Venous leg ulceration is caused by chronic venous insufficiency and affects millions of adults worldwide who suffer prolonged healing episodes and due to underlying pathophysiology ulcer recurrence is common after healing. Compression therapy is the current best practice for managing venous leg ulcer since it provides constant pressure, which promotes circulation in the lower limbs. Nevertheless, the healing outcomes of venous leg ulcer vary considerably. Physical activity may be an effective adjunct treatment to improve ulcer healing outcomes. However, a low level of physical activity level is observed in this cohort. Objective To identify the barriers and enablers that affect physical activity participation in people with venous leg ulcers. Design A systematic review of qualitative studies using the mega-aggregation approach. Methods We followed the Joanna Briggs Institute methodology for systematic reviews of qualitative evidence. We searched MEDLINE, CINAHL PLUS, PsycINFO and Emcare to identify relevant articles published in English from 1806 to January 2021. Two reviewers independently screened and selected articles against inclusion criteria. Eligible studies were appraised for methodological quality using Joanna Briggs Institute Critical Appraisal tool. Qualitative data were extracted manually. Theoretical Domain Framework was used to map barriers and enablers to physical activity participation. Results Eighteen studies were included in this review. The main barriers and enablers identified in this review that influence physical activity engagement in people with venous leg ulcers are as follows: understanding the chronic nature of venous leg ulcers and the reasons for undertaking physical activities; specific beliefs that people hold about their own capabilities; pain related to wound and compression therapy; information and supports received from treating clinicians; feeling of fear and embarrassment. The confidence level for most of the synthesis findings was moderate to low. Conclusions Our review identified people with venous leg ulcers experience significant challenges preventing them from engaging in physical activity. Factors such as knowledge of physical activity, availability of information, and self-belief may be particularly important for promoting physical activity in this cohort. Future interventions are recommended to provide educational information and clear instructions to improve participation. Further research is needed to explore potential interventions that may change physical activity behaviour in this population group. Registration PROSPERO CRD42021238579.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The results of the qualitative systematic review showcase similarities in participants' voices which for the current study were crucial for gaining a better understanding of the process of engaging in self-management strategies.
“Their results showcase similarities in participants’ voices which for the current study, were crucial for gaining a better understanding of the process of engaging in self-management strategies.”
From Application and challenges of using a Constructivist Grounded Theory methodology to address an undertheorized clinical challenge: A discussion paper (2024) · cites this paper as Qiu et al., 2022
The suggested outcomes of the qualitative systematic review resonated with the generated data and subsequent emerging categories.
“Their suggested outcomes resonated with the generated data and subsequent emerging categories.”
From Application and challenges of using a Constructivist Grounded Theory methodology to address an undertheorized clinical challenge: A discussion paper (2024) · cites this paper as Qiu et al., 2022
A recent qualitative systematic review outlined barriers and facilitators to physical activity for individuals living with a venous leg ulcer.
“A recent qualitative systematic review outlined barriers and facilitators to physical activity for individuals living with a venous leg ulcer (Qiu et al., 2022).”
From Application and challenges of using a Constructivist Grounded Theory methodology to address an undertheorized clinical challenge: A discussion paper (2024) · cites this paper as Qiu et al., 2022
Cites
Shamseer, L., Moher, D., Clarke, M., Ghersi, D., Liberati, A., Petticrew, M., Shekelle, P., Stewart, L. A., & the PRISMA-P Group (2015) · BMJ · doi:10.1136/bmj.g7647 · Cited by 13,120 · see citing works
JBI Manual for Evidence Synthesis
(2020) · JBI eBooks · doi:10.46658/jbimes-20-01 · Cited by 4,165 · see citing works
Atkins, L., Francis, J., Islam, R., O’Connor, D., Patey, A., Ivers, N., Foy, R., Duncan, E. M., Colquhoun, H., Grimshaw, J. M., et al. (2017) · Implementation Science · doi:10.1186/s13012-017-0605-9 · Cited by 3,819 · see citing works
Lockwood, C., Munn, Z., & Porritt, K. (2015) · International Journal of Evidence-Based Healthcare · doi:10.1097/xeb.0000000000000062 · Cited by 2,456 · see citing works
Why is changing health-related behaviour so difficult?
Kelly, M. P., & Barker, M. E. (2016) · Public Health · doi:10.1016/j.puhe.2016.03.030 · Cited by 1,138 · see citing works
Establishing confidence in the output of qualitative research synthesis: the ConQual approach.
Munn, Z., Porritt, K., Lockwood, C., Aromataris, E., & Pearson, A. (2014) · BMC Medical Research Methodology · doi:10.1186/1471-2288-14-108 · Cited by 803 · see citing works
O’Donnell, T. F., Passman, M. A., Marston, W. A., Ennis, W. J., Dalsing, M. C., Kistner, R. L., Lurie, F., Henke, P. K., Gloviczki, M. L., Eklöf, B., et al. (2014) · Journal of Vascular Surgery · doi:10.1016/j.jvs.2014.04.049 · Cited by 729 · see citing works
Sullivan, A. N., & Lachman, M. E. (2017) · Frontiers in Public Health · doi:10.3389/fpubh.2016.00289 · Cited by 458 · see citing works
Mann, T. L., de Ridder, D. T. D., & Fujita, K. (2013) · Health Psychology · doi:10.1037/a0028533 · Cited by 455 · see citing works
Perceived Control Over Aging-Related Declines
Lachman, M. E. (2006) · Current Directions in Psychological Science · doi:10.1111/j.1467-8721.2006.00453.x · Cited by 331 · see citing works
Management of Patients With Venous Leg Ulcers: Challenges and Current Best Practice
Franks, P. J., Barker, J., Collier, M. A., Gethin, G., Haesler, E., Jawień, A., Laeuchli, S., Mosti, G. B., Probst, S., & Weller, C. D. (2016) · Journal of Wound Care · doi:10.12968/jowc.2016.25.sup6.s1 · Cited by 313 · see citing works
Self-citationLiving with a venous leg ulcer: a descriptive study of patients’experiences
Walshe, C. (1995) · Journal of Advanced Nursing · doi:10.1111/j.1365-2648.1995.tb03110.x · Cited by 260 · see citing works
Hennessy, E. A., Johnson, B. T., Acabchuk, R. L., McCloskey, K., & Stewart-James, J. (2019) · Health Psychology Review · doi:10.1080/17437199.2019.1679654 · Cited by 249 · see citing works
A forever healing: The lived experience of venous ulcer disease
Chase, S. K., Melloni, M., & Savage, A. (1997) · Journal of Vascular Nursing · doi:10.1016/s1062-0303(97)90004-2 · Cited by 182 · see citing works
Cognitive control in the self-regulation of physical activity and sedentary behavior
Buckley, J., Cohen, J. D., Kramer, A. F., McAuley, E., & Mullen, S. P. (2014) · Frontiers in Human Neuroscience · doi:10.3389/fnhum.2014.00747 · Cited by 165 · see citing works
Living with a chronic leg ulcer: an insight into patients' experiences and feelings
Douglas, V. (2001) · Journal of Wound Care · doi:10.12968/jowc.2001.10.9.26318 · Cited by 160 · see citing works
Self-Regulation and Self-Control
Baumeister, R. F. (2018) · Routledge eBooks · doi:10.4324/9781315175775 · Cited by 157 · see citing works
Wilkins, L. W., & Kluwer, W. (2020) · Lippincott Williams & Wilkins eBooks · Cited by 155 · see citing works
de Bruin, M., Sheeran, P., Kok, G., Hiemstra, A., Prins, J. M., Hospers, H. J., & van Breukelen, G. (2012) · Health Psychology · doi:10.1037/a0027425 · Cited by 143 · see citing works
Chronic Wound Infection and Antimicrobial Use
Landis, S. J. (2008) · Advances in Skin & Wound Care · doi:10.1097/01.asw.0000323578.87700.a5 · Cited by 136 · see citing works
Publicly reported wound healing rates: the fantasy and the reality.
Fife, C. E., Eckert, K. A., & Carter, M. J. (2018) · Advances in Wound Care · doi:10.1089/wound.2017.0743 · Cited by 132 · see citing works
Finlayson, K. J., Wu, M., & Edwards, H. E. (2015) · International Journal of Nursing Studies · doi:10.1016/j.ijnurstu.2015.02.016 · Cited by 116 · see citing works
Wound healing society 2015 update on guidelines for venous ulcers
Marston, W. A., Tang, J. C., Kirsner, R. S., & Ennis, W. J. (2015) · Wound Repair and Regeneration · doi:10.1111/wrr.12394 · Cited by 106 · see citing works
Cost of managing patients with venous leg ulcers
Phillips, C. J., Humphreys, I., Thayer, D. S., Elmessary, M. A., Collins, H., Roberts, C., Naik, G., & Harding, K. G. (2020) · International Wound Journal · doi:10.1111/iwj.13366 · Cited by 85 · see citing works
Weller, C. D., Richards, C., Turnour, L., & Victoria Team (2021) · Frontiers in Pharmacology · doi:10.3389/fphar.2021.663570 · Cited by 79 · see citing works
Self-citationPain in persons with chronic venous leg ulcers: A systematic review and meta‐analysis
Leren, L., Johansen, E. A., Eide, H., Falk, R. S., Juvet, L. K., & Ljosaa, T. M. (2020) · International Wound Journal · doi:10.1111/iwj.13296 · Cited by 75 · see citing works
Finlayson, K. J., Parker, C. N., Miller, C., Gibb, M., Kapp, S., Ogrin, R., Anderson, J., Coleman, K., Smith, D., & Edwards, H. E. (2018) · International Wound Journal · doi:10.1111/iwj.12911 · Cited by 71 · see citing works
Hecke, A. V., Grypdonck, M., Beele, H., Vanderwee, K., & Defloor, T. (2011) · Journal of Clinical Nursing · doi:10.1111/j.1365-2702.2010.03546.x · Cited by 67 · see citing works
Impact of venous ulcers on patients' quality of life: an integrative review
Joaquim, F. L., Silva, R. M. C. R. A., García‐Caro, M. P., Cruz‐Quintana, F., & Pereira, E. R. (2018) · Revista Brasileira de Enfermagem · doi:10.1590/0034-7167-2017-0516 · Cited by 66 · see citing works
Evidence‐based (S3) guidelines for diagnostics and treatment of venous leg ulcers
specialists., T. G. I. A. D. W. R. A. M. I. S. T. D. P. I. W. T. O. T. (. H. A. P. O. R. O. T. P. I. C. T. G. I. B. O. T. R. O. S. R. A. C. O. A. A. E. G. M. P. T. D. I. I. A. A. G. F. T. E. D. A. T. O. V. L. U. B. D. O. O. M. (2016) · Journal of the European Academy of Dermatology and Venereology · doi:10.1111/jdv.13848 · Cited by 63 · see citing works
Chronic leg ulcers, part 2: do they affect a patient's social life?
Brown, A. (2005) · British Journal of Nursing · doi:10.12968/bjon.2005.14.18.19888 · Cited by 62 · see citing works
Adherence to physical activity in adults with chronic diseases: ELSA-Brasil
Forechi, L., Mill, J. G., Griep, R. H., Santos, I. S., Pitanga, F. J. G., & Molina, M. D. C. B. (2018) · Revista de Saúde Pública · doi:10.11606/s1518-8787.2018052000215 · Cited by 61 · see citing works
A case-control study of risk factors of chronic venous ulceration in patients with varicose veins
Abelyan, G., Abrahamyan, L., & Yenokyan, G. (2017) · Phlebology The Journal of Venous Disease · doi:10.1177/0268355516687677 · Cited by 56 · see citing works
Patient perspectives of their leg ulcer journey
Green, J., Jester, R., McKinley, R. K., & Pooler, A. (2013) · Journal of Wound Care · doi:10.12968/jowc.2013.22.2.58 · Cited by 54 · see citing works
Psychosocial Aspects in Patients With Chronic Leg Ulcers
Platsidaki, E., Kouris, A., & Christodoulou, C. (2017) · WOUNDS A Compendium of Clinical Research and Practice · doi:10.25270/wnds/2017.10.306310 · Cited by 54 · see citing works
Processes underlying adherence to leg ulcer treatment: A qualitative field study
Hecke, A. V., Verhaeghe, S. T. L., Grypdonck, M., Beele, H., & Defloor, T. (2010) · International Journal of Nursing Studies · doi:10.1016/j.ijnurstu.2010.07.001 · Cited by 53 · see citing works
Strategies and challenges in the treatment of chronic venous leg ulcers
Ren, S.-Y., Liu, Y., Zhu, G.-J., Liu, M., Shi, S., Ren, X.-D., Hao, Y.-G., & Gao, R.-D. (2020) · World Journal of Clinical Cases · doi:10.12998/wjcc.v8.i21.5070 · Cited by 47 · see citing works
Smith, D. E., Lane, R., McGinnes, R., O’Brien, J., Johnston, R. V., Bugeja, L. C., Victoria Team, & Weller, C. D. (2018) · International Wound Journal · doi:10.1111/iwj.12885 · Cited by 45 · see citing works
Self-citationRoaldsen, K. S., Biguet, G., & Elfving, B. (2010) · Clinical Rehabilitation · doi:10.1177/0269215510371424 · Cited by 45 · see citing works
Factors Related To Venous Ulceration
Vlajinac, H., Marinković, J., Maksimović, M., & Radak, D. J. (2013) · Angiology · doi:10.1177/0003319713508218 · Cited by 43 · see citing works
Living with venous leg ulceration: issues concerning adherence
Mudge, E. J., Holloway, S., Simmonds, W., & Price, P. (2006) · British Journal of Nursing · doi:10.12968/bjon.2006.15.21.22374 · Cited by 42 · see citing works
Assessment of pain in chronic wounds: A survey of Australian health care practitioners
Frescos, N. (2018) · International Wound Journal · doi:10.1111/iwj.12951 · Cited by 42 · see citing works
The experience of self‐management following venous leg ulcer healing
Kapp, S., & Miller, C. (2014) · Journal of Clinical Nursing · doi:10.1111/jocn.12730 · Cited by 40 · see citing works
Fear‐avoidance beliefs and pain as predictors for low physical activity in patients with leg ulcer
Roaldsen, K. S., Elfving, B., Stanghelle, J. K., Talme, T., & Mattsson, E. (2009) · Physiotherapy Research International · doi:10.1002/pri.433 · Cited by 37 · see citing works
Venous leg ulcer management in Australian primary care: Patient and clinician perspectives
Weller, C. D., Richards, C., Turnour, L., & Victoria Team (2020) · International Journal of Nursing Studies · doi:10.1016/j.ijnurstu.2020.103774 · Cited by 36 · see citing works
Self-citationAdjuvant therapies in venous leg ulcer management: A scoping review
V. Team, Chandler, P. G., & Weller, C. (2019) · Wound Repair and Regeneration · doi:10.1111/wrr.12724 · Cited by 33 · see citing works
Self-citationWeller, C. D., Richards, C., Turnour, L., & Victoria Team (2020) · International Wound Journal · doi:10.1111/iwj.13334 · Cited by 30 · see citing works
Self-citationThe perspectives of adults with venous leg ulcers on exercise: an exploratory study
O’Brien, J., Finlayson, K. J., Kerr, G., & Edwards, H. E. (2014) · Journal of Wound Care · doi:10.12968/jowc.2014.23.10.496 · Cited by 29 · see citing works
Qiu, Y., Osadnik, C. R., Victoria Team, & Weller, C. D. (2022) · Wound Repair and Regeneration · doi:10.1111/wrr.12995 · Cited by 28 · see citing works
Self-citationHecke, A. V., Verhaeghe, S. T. L., Grypdonck, M., Beele, H., Flour, M., & Defloor, T. (2010) · Journal of Advanced Nursing · doi:10.1111/j.1365-2648.2010.05539.x · Cited by 24 · see citing works
Nutritional intake and physical activity in leg ulcer patients
Wissing, U., Unosson, M., Lennernäs, M. A. ‐., & Ek, A. (1997) · Journal of Advanced Nursing · doi:10.1046/j.1365-2648.1997.1997025571.x · Cited by 23 · see citing works
Quality of life of patients with hard-to-heal leg ulcers: a review of nursing documentation
Olsson, M. B., & Friman, A. (2020) · British Journal of Community Nursing · doi:10.12968/bjcn.2020.25.sup12.s12 · Cited by 19 · see citing works
Repercussões sociais vivenciadas pela pessoa idosa com úlcera venosa
Aguiar, A. C. D. S. A., Sadigursky, D., Martins, L. A., Menezes, T. M. D. O., Santos, A. L. D. S., & dos Reis, L. A. (2016) · Revista gaúcha de enfermagem · doi:10.1590/1983-1447.2016.03.55302 · Cited by 19 · see citing works
Kesterton, S., Crank, H., Tew, G. A., Michaels, J. A., Gumber, A., McIntosh, E., King, B., & Klonizakis, M. (2019) · International Wound Journal · doi:10.1111/iwj.13252 · Cited by 15 · see citing works
General practitioners’ knowledge of leg ulcer treatment in primary healthcare: an interview study
Friman, A., Edström, D. W., Ebbeskog, B., & Edelbring, S. (2020) · Primary Health Care Research & Development · doi:10.1017/s1463423620000274 · Cited by 15 · see citing works
Weller, C. D., Bouguettaya, A., Britt, H. C., & Harrison, C. M. (2020) · Wound Repair and Regeneration · doi:10.1111/wrr.12820 · Cited by 12 · see citing works
Self-citationBPS1: Minimising pain at wound dressing-related procedures
Jones, M. L. (2013) · British Journal of Healthcare Assistants · doi:10.12968/bjha.2013.7.7.326 · Cited by 5 · see citing works
Improving quality of life in venous leg ulceration: a case study
Bentley, J. (2006) · British Journal of Nursing · doi:10.12968/bjon.2006.15.sup2.21234 · Cited by 5 · see citing works
Venous Stasis Ulcers in the Patient Who Is Obese
Gates, J., Davis, J. M., & Evans, E. (2005) · Journal of Wound Ostomy and Continence Nursing · doi:10.1097/00152192-200511000-00015 · Cited by 4 · see citing works
Murli, N. L., Lee, T. C., & Ml, B. (2013) · PubMed · Cited by 4 · see citing works
Qiu, Y., Victoria Team, Osadnik, C. R., & Weller, C. D. (2021) · JBI Evidence Synthesis · doi:10.11124/jbies-20-00549 · Cited by 3 · see citing works
Self-citationThe impact of venous ulcer pain: what can the patient teach us?
Stevens, H. E. (2006) · British Journal of Community Nursing · doi:10.12968/bjcn.2006.11.sup6.22432 · Cited by 2 · see citing works
Current understanding on venous leg ulcer
ALOK, U., Bhardwaj, P., Singh, A., & Cherian, J. J. (2014) · Indian Journal of Pharmaceutical and Biological Research · doi:10.30750/ijpbr.2.3.6 · Cited by 2 · see citing works
Yıldız, C. E., Conkbayır, C., Tolgay, H. E., Çeviker, K., Canikoğlu, M., Sayın, Ö. A., & Uğurlucan, M. (2017) · Archives of Medical Science · doi:10.5114/aoms.2017.67289 · Cited by 2 · see citing works
Flagged first, then by citations
4 of the 68 references couldn’t be matched to a known paper.
Cited by
Sorted by citations
Prevention strategies for the recurrence of venous leg ulcers: A scoping review
He, B., Shi, J., Li, L., Ma, Y., Zhao, H. Q., Qin, P., & Ma, P. (2024) · International Wound Journal · doi:10.1111/iwj.14759 · Cited by 19 · see citing works
Bobbink, P., Larkin, P., & Probst, S. (2024) · International Journal of Nursing Studies Advances · doi:10.1016/j.ijnsa.2024.100199 · Cited by 15 · see citing works
Evans, C., Hassanein, Z. M., Bains, M., Bennett, C. L., Bjerrum, M. B., Edgley, A., Edwards, D. J., Porritt, K. A., & Salmond, S. W. (2024) · JBI Evidence Synthesis · doi:10.11124/jbies-24-00025 · Cited by 19 · see citing works
Fan, Q., Meng, Y., Nie, Z., Xie, S., & Chen, C. (2023) · Frontiers in Endocrinology · doi:10.3389/fendo.2023.1230955 · Cited by 7 · see citing works
The Chronic Wound–Related Pain Model
Woo, K. Y. (2024) · Clinics in Geriatric Medicine · doi:10.1016/j.cger.2023.12.013 · Cited by 6 · see citing works
Schick, R., Staub-Buset, C., Vujic, G., Lachappelle, S., & Panfil, E. (2024) · Journal of Tissue Viability · doi:10.1016/j.jtv.2024.12.001 · Cited by 5 · see citing works
Qiu, Y., Osadnik, C. R., & Victoria Team (2023) · Journal of Tissue Viability · doi:10.1016/j.jtv.2023.03.004 · Cited by 5 · see citing works
Self-citationBobbink, P., Gschwind, G., Larkin, P. J., & Probst, S. (2024) · Qualitative Health Research · doi:10.1177/10497323241285692 · Cited by 5 · see citing works
Zhang, Y., Li, K., Wu, S., Zhu, K., Xie, F., Zhu, B., Wang, L., & Wang, W. (2025) · BMC Complementary Medicine and Therapies · doi:10.1186/s12906-025-04814-0 · Cited by 4 · see citing works
Qiu, Y., Osadnik, C. R., Brusco, N. K., Sussman, G., Reeves, J., Gleghorn, L., Weller, C. D., & Victoria Team (2023) · Frontiers in Medicine · doi:10.3389/fmed.2023.1305594 · Cited by 3 · see citing works
Self-citationBoyers, D., Cruickshank, M., Aucott, L., Kennedy, C., Manson, P., Bachoo, P., & Brazzelli, M. (2024) · Health Technology Assessment · doi:10.3310/twcg3912 · Cited by 3 · see citing works
Ampomah, M. A., Anum, A., Apedo, S. K., Manu, E., Narh, C. T., Kushitor, M. K., Amegan-Aho, K. H., Hood, A., & Kirkham, F. J. (2025) · Discover Social Science and Health · doi:10.1007/s44155-025-00151-2 · Cited by 1 · see citing works
O’Brien, J., McCann, D., Parker, C. N., Finlayson, K. J., & Jull, A. (2025) · The International Journal of Lower Extremity Wounds · doi:10.1177/15347346251321550
Barriers and factors associated with physical activity in patients with chronic venous insufficiency
Domingues, W. J. R., de Oliveira, M. D., Silva, P. L. D. S. E., Campelo, P. R. D. S., dos Santos, N. J. N., dos Santos, S. V. A., Arêas, G. P. T., & Simões, C. F. (2025) · Phlebology The Journal of Venous Disease · doi:10.1177/02683555251375154
- Authors
- Qiu, Y., Team, V., Osadnik, C. R., & Weller, C. D.
- Affiliations
- Monash University (AU)
- Corresponding author
- Qiu, Yunjing
- Venue
- International Journal of Nursing Studies
- Publisher
- Elsevier BV
- Published
- 2022-11
- Volume
- 135
- Pages
- 104329
- ISSN
- 0020-7489 (ISSN-L)
- OpenAlex
- W4286639460
- Cited by
- 14
- References
- 68
- Citations by year
- 2025: 4 · 2024: 7 · 2023: 3
- FWCI
- 0.83
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- Locations
- International Journal of Nursing Studies (publishedVersion)
- PubMed (publishedVersion)
- Funders
- Monash University
- Topics
- Health Sciences › Medicine › Surgery › Diagnosis and Treatment of Venous Diseases
- Health Sciences › Medicine › Physiology › Physical Activity and Health
- Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
- Keywords
- venous leg ulcers, physical activity, barriers and facilitators, chronic venous insufficiency, compression therapy, wound pain, self-efficacy, fear and embarrassment, patient education, ulcer healing, behavior change
- MeSH terms
- Adult, Humans, Leg Ulcer, Ulcer, Varicose Ulcer, Wound Healing, Exercise, Qualitative Research
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
