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Cited by 11Sperm and Testicular FunctionSmoking Behavior and CessationPrenatal Substance Exposure Effects

Decreased sperm counts in Swedish users of oral tobacco

Open access
Kimblad, Agnes, Ollvik, Gustav, Lindh, Christian H, Axelsson, Jonatan·2022·Andrology
DOI 10.1111/andr.13198PMC PMC9543234
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Abstract

Background: Smoke‐free tobacco via moist oral snuff (snus) is used daily in more than 20% of Swedish men. Negative effects of cigarette smoking on sperm parameters are well documented, unlike for snuff, despite relevance also for other smoke‐free nicotine products. Objectives: We wanted to investigate whether reproductive parameters differed between users and non‐users of snuff, and whether the amount of snuff and nicotine exposure mattered. Materials and methods: Men (n = 613) from the general population, recruited 2000–2010, were physically examined, answered questions on smoking and snuff use, and delivered urine, blood and semen samples. Sperm concentration, total sperm count, semen volume, percent morphologically normal and progressively motile sperm, and DNA fragmentation index (by the Sperm Chromatin Structure Assay) and reproductive hormones were analysed. Nicotine exposure was measured through urinary levels of cotinine. We used general linear models, with adjustments including cigarette smoking, and for semen parameters also abstinence time. Results: After adjustments, total sperm count was 24% lower (P = 0.03) and testosterone 14% higher (P < 0.001) in 109 users of snuff than in non‐users, whereas cotinine was positively associated with testosterone and oestradiol (P < 0.001). Numbers of boxes of snuff used per week were associated with testosterone and FSH (P < 0.001). Discussion: Applied to the general population, the consumption of smoke‐free tobacco by the use of snuff was associated with a lower sperm count and a higher testosterone, for which the extent seemed to play a role. Conclusions: Independent of smoking, consumption of snuff was associated with lower total sperm count and different hormone levels. Applying these results to a reported association between sperm count and the chance of pregnancy, men who used snuff would have about a 10% lower chance of fathering a child.

AI snapshot

Written from the paper’s full text.

TL;DR

In a cross-sectional study of 613 Swedish men, self-reported use of moist oral snuff was associated with a 24% lower total sperm count and higher testosterone, independent of cigarette smoking. The authors estimate this difference corresponds to about a 10% lower chance of fathering a child, though causality cannot be established.

Key findings

  • Total sperm count was 24% lower in snuff users than non-users (120 × 10⁶ vs. 160 × 10⁶; difference 34 million; P = 0.03), adjusted for smoking and abstinence time.
  • Testosterone was higher in snuff users (24 vs. 21 nmol/L; P < 0.001), and FSH was also higher (5.9 vs. 4.3 IU/L; P = 0.04).
  • Urinary cotinine was positively associated with testosterone and oestradiol (P < 0.001 for both) and negatively associated with total sperm count (P = 0.03 in text; table reports P = 0.02).
  • Number of boxes of snuff used per week was positively associated with testosterone and FSH (both P < 0.001), but not with semen parameters; the negative association with total sperm count was not statistically significant (P = 0.07).
  • Applying a reported 3% lower chance of fathering a child per 10-million decrease in total sperm count below 200 million, the authors estimate snuff users would have about a 9.8% lower chance of fathering a child.

Methods

  • Observational cross-sectional study of 613 men from the general Swedish population, recruited in two cohorts (2000–2001 and 2008–2010); 538 had data on snuff use, and 109–112 were snuff users depending on outcome.
  • Participants underwent physical examination, questionnaires on smoking/snuff use, and provided urine, blood, and semen samples; semen parameters included sperm concentration, total sperm count, volume, morphology, progressive motility, DNA fragmentation index (SCSA), and total progressively motile sperm count.
  • Urinary cotinine was measured by LC–MS/MS in 396 men; reproductive hormones were measured by cohort-specific immunoassays. General linear models were adjusted for cigarette smoking and abstinence time (semen parameters) or smoking and cohort (hormones), with additional separate adjustments for chronic disease, varicocele, alcohol, maternal occupation, and maternal/paternal smoking.

Limitations

  • The authors state that several variables were available only in part of the men (e.g., weekly boxes of snuff, maternal occupational field), which may have led to underestimation of true associations; adjustments for maternal occupation and parental smoking may not fully capture socioeconomic status.
  • The authors state that the cross-sectional design cannot determine causality, and that other factors related to snuff use or nicotine exposure may explain the associations; cotinine is also described as an imperfect marker due to inter-individual metabolic variation.
  • The authors note that the lack of a significant association between weekly boxes of snuff and semen parameters might reflect individual variation in oral retention time, and that larger studies are needed; the text also makes evident that the sample is limited to young Swedish men, which may affect generalizability.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1111/andr.13198

Cites

33 of 33 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

16 of 35 cited sources checked · 12 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    No association was found between snuff use and reproductive hormones in the Richthoff and Danish studies.

    “No association was found between snuff use and reproductive hormones in either of these two studies.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [6] Richthoff J, Elzanaty S, Rylander L, Hagmar L, Giwercman A. Association between tobacco exposure and reproductive parameters in adolescent males. Int J Androl. 2007; 0(0): 070322041217003. 10.1111/j.1365-2605.2007.00752.x 17376217 source
    • cites [7] Holmboe SA, Priskorn L, Jensen TK, Skakkebaek NE, Andersson AM, Jorgensen N. Use of e‐cigarettes associated with lower sperm counts in a cross‐sectional study of young men from the general population. Hum Reprod. 2020; 35(7): 1693‐ 1701. 10.1093/humrep/deaa089 32558890 source
  • Premisecitation

    Experimental studies speak in a similar direction regarding decreased sperm counts after nicotine exposure.

    “which however speak in a similar direction regarding decreased sperm counts after nicotine exposure. 9 , 10”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [9] Budin SB, Kho JH, Lee JH, et al. Low‐dose nicotine exposure induced the oxidative damage of reproductive organs and altered the sperm characteristics of adolescent male rats. Malays J Med Sci. 2017; 24(6): 50‐ 57. 10.21315/mjms2017.24.6.6 29379386 PMC5771515 source
    • cites [10] Oyeyipo IP, Raji Y, Emikpe BO, Bolarinwa AF. Effects of nicotine on sperm characteristics and fertility profile in adult male rats: A possible role of cessation. J Reprod Infertil. 2011; 12(3): 201‐ 7. 23926503 PMC3719292
  • Premisecitation

    Animal studies have reported that nicotine affected semen parameters in rats, including their sperm counts.

    “Further, animal studies have reported that nicotine affected semen parameters in rats, including their sperm counts. 9 , 10”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [9] Budin SB, Kho JH, Lee JH, et al. Low‐dose nicotine exposure induced the oxidative damage of reproductive organs and altered the sperm characteristics of adolescent male rats. Malays J Med Sci. 2017; 24(6): 50‐ 57. 10.21315/mjms2017.24.6.6 29379386 PMC5771515 source
    • cites [10] Oyeyipo IP, Raji Y, Emikpe BO, Bolarinwa AF. Effects of nicotine on sperm characteristics and fertility profile in adult male rats: A possible role of cessation. J Reprod Infertil. 2011; 12(3): 201‐ 7. 23926503 PMC3719292
  • Interpretationcitation

    The lower total sperm count in men who used snuff (120×10^6 vs. 160×10^6) may be clinically relevant, despite being above the lower WHO reference limit.

    “the lower total sperm count in men who used snuff (120×106 vs. 160×106) may be clinically relevant, despite being above the lower WHO reference limit, 39”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [39] Flaskerud JH, DeLilly CR. Social determinants of health status. Issues Ment Health Nurs. 2012; 33(7): 494‐ 497. 10.3109/01612840.2012.662581 22757603 PMC3710744 source

      The section on SES-related risk factors discusses smoking and disease, but not snuff use or sperm counts. Searches for the reported 120×10^6 versus 160×10^6 comparison, semen measures, and the WHO reference limit found no relevant passage in our copy. (LLM, conf=0.78)

      Experimental — accuracy not yet measured
  • Findingown data

    Numbers of boxes of snuff used per week were positively associated with FSH.

    “Numbers of boxes of snuff used per week were associated with testosterone and FSH (P < 0.001).”
    • Also stated in: § Association between the numbers of boxes of snuff consumed per week and reproductive parameters · plain
      “such an association was found with both testosterone and FSH (both positive and with p < 0.001, Table 3).”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. 18
  • May combine two claims. 17

  • Classified as probably not a substantial claim.

    Premisecitation

    A study in rats reported impaired sperm parameters after treatment with nicotine.

    “a study in rats reported impaired sperm parameters after treatment with nicotine. 9”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [9] Budin SB, Kho JH, Lee JH, et al. Low‐dose nicotine exposure induced the oxidative damage of reproductive organs and altered the sperm characteristics of adolescent male rats. Malays J Med Sci. 2017; 24(6): 50‐ 57. 10.21315/mjms2017.24.6.6 29379386 PMC5771515 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Socioeconomic status does affect health outcomes via factors that include the use of tobacco.

    “having in mind that socioeconomic status does affect health outcomes via factors that include the use of tobacco. 38”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [38] Vadillo MA, Konstantinidis E, Shanks DR. Underpowered samples, false negatives, and unconscious learning. Psychon Bull Rev. 2016; 23(1): 87‐ 102. 10.3758/s13423-015-0892-6 26122896 PMC4742512 source

      The paper’s sections on effect sizes and statistical power and on publication bias in awareness tests discuss unconscious learning, not health outcomes. Searches for socioeconomic status, tobacco use, and their relationship to health found no passage addressing the claim; the cited paper therefore does not verify it. (LLM, conf=0.76)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Richthoff et al. concluded that cigarette smoking, but not the use of snuff, among young healthy men was associated with lower sperm counts.

    “Richthoff et al. concluded that cigarette smoking, but not the use of snuff (which 51 men used) among young healthy men was associated with lower sperm counts. 6”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [6] Richthoff J, Elzanaty S, Rylander L, Hagmar L, Giwercman A. Association between tobacco exposure and reproductive parameters in adolescent males. Int J Androl. 2007; 0(0): 070322041217003. 10.1111/j.1365-2605.2007.00752.x 17376217 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation

    Hormone levels were measured using validated assays (ElectroChemiLuminiscenceImmunoassay in cohort 2, automated fluorescence detection in cohort 1), and free testosterone was calculated according to a published method.

    “Levels of testosterone, luteinising hormone (LH), follicle‐stimulating hormone (FSH) and sex‐hormone binding globulin (SHBG) that were available from both cohorts, were measured in the second cohort by use of ElectroChemiLuminiscenceImmunoassay (Roche Cobas) as previously described in detail. 26 In the first cohort, recruited around year 2000, these hormones were measured by use of an automated”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [26] Hamilton JA, Cissen M, Brandes M, et al. Total motile sperm count: A better indicator for the severity of male factor infertility than the WHO sperm classification system. Hum Reprod. 2015; 30(5): 1110‐ 21. 10.1093/humrep/dev058 25788568 source

      The Fertility work-up section mentions a midluteal progesterone measurement, and the Semen analysis section describes sperm testing, but neither addresses the claimed hormone assays or free-testosterone calculation. Searches for ElectroChemiLuminiscenceImmunoassay, Roche Cobas, automated fluorescence detection, and free testosterone found no relevant passage in our copy (page numbers unavailable). (LLM, conf=0.75)

      Experimental — accuracy not yet measured
    • cites [25] Richthoff J, Spano M, Giwercman YL, et al. The impact of testicular and accessory sex gland function on sperm chromatin integrity as assessed by the sperm chromatin structure assay (SCSA). Hum Reprod. 2002; 17(12): 3162‐ 3169. 10.1093/humrep/17.12.3162 12456618 source
    • cites [27] Axelsson J, Rylander L, Rignell‐Hydbom A, Jonsson BA, Lindh CH, Giwercman A. Phthalate exposure and reproductive parameters in young men from the general Swedish population. Environ Int. 2015; 85: 54‐ 60. 10.1016/j.envint.2015.07.005 26318515 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Socioeconomic status has been reported negatively associated with semen quality.

    “which has been reported negatively associated with semen quality, 8”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [8] Pärn T, Grau Ruiz R, Kunovac Kallak T, et al. Physical activity, fatness, educational level and snuff consumption as determinants of semen quality: Findings of the ActiART study. Reprod BioMed Online. 2015; 31(1): 108‐ 119. 10.1016/j.rbmo.2015.03.004 25999214 source

      In “Educational level, snuff consumption and semen quality” (page unavailable), the paper reports earlier studies finding that higher education was associated with lower semen quality. Education is only one aspect of socioeconomic status, however, and the ActiART study found the opposite association in its own sample. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Study design and conductown data

    Our article included a higher number of snuff-users than the articles by Pärn et al., Richthoff et al., and Holmboe et al., and thus possibly had a greater statistical power.

    “In comparison to the articles by Pärn et al., 8 Richthoff et al. 16 and Holmboe et al., 7 our article included a higher number of snuff‐users, and thus possibly had a greater statistical power.”
    Quote in the paperNot a substantial claim3 of 3 sources checked
    • cites [8] Pärn T, Grau Ruiz R, Kunovac Kallak T, et al. Physical activity, fatness, educational level and snuff consumption as determinants of semen quality: Findings of the ActiART study. Reprod BioMed Online. 2015; 31(1): 108‐ 119. 10.1016/j.rbmo.2015.03.004 25999214 source
    • cites [16] Richthoff J, Elzanaty S, Rylander L, Hagmar L, Giwercman A. Association between tobacco exposure and reproductive parameters in adolescent males. Int J Androl. 2008; 31(1): 31‐ 9. 10.1111/j.1365-2605.2007.00752.x 17376217 source
    • cites [7] Holmboe SA, Priskorn L, Jensen TK, Skakkebaek NE, Andersson AM, Jorgensen N. Use of e‐cigarettes associated with lower sperm counts in a cross‐sectional study of young men from the general population. Hum Reprod. 2020; 35(7): 1693‐ 1701. 10.1093/humrep/deaa089 32558890 source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    A study by Pärn et al. in men recruited from a fertility clinic reported that men who used snuff had lower sperm counts and motility than non-users.

    “However, a study by Pärn et al. in men recruited from a fertility clinic (in which 17 men used snuff) has reported that men who used snuff had lower sperm counts and motility than the non‐users. 8”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [8] Pärn T, Grau Ruiz R, Kunovac Kallak T, et al. Physical activity, fatness, educational level and snuff consumption as determinants of semen quality: Findings of the ActiART study. Reprod BioMed Online. 2015; 31(1): 108‐ 119. 10.1016/j.rbmo.2015.03.004 25999214 source

  • May combine two claims.

    Premisecitation

    A study in Danish men found that both daily cigarette and e-cigarette users had decreased sperm counts.

    “A similar result was found in Danish men (of whom 68 used snuff daily), in whom both daily cigarette and e‐cigarette users had decreased sperm counts. 7”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [7] Holmboe SA, Priskorn L, Jensen TK, Skakkebaek NE, Andersson AM, Jorgensen N. Use of e‐cigarettes associated with lower sperm counts in a cross‐sectional study of young men from the general population. Hum Reprod. 2020; 35(7): 1693‐ 1701. 10.1093/humrep/deaa089 32558890 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The amount of nicotine a human absorbs is 1-1.5 mg/cigarette and 3.6 mg/portion of oral snuff.

    “The amount of nicotine a human absorbs has been reported to be 1–1.5 mg/cigarette 11 and 3.6 mg/portion of oral snuff. 12”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [11] Prochaska JJ, Benowitz NL. Current advances in research in treatment and recovery: Nicotine addiction. Sci Adv. 2019; 5(10): eaay9763. 10.1126/sciadv.aay9763 31663029 PMC6795520 source
    • cites [12] Benowitz NL, Porchet H, Sheiner L, Jacob P, 3rd. Nicotine absorption and cardiovascular effects with smokeless tobacco use: Comparison with cigarettes and nicotine gum. Clin Pharmacol Ther. 1988; 44(1): 23‐ 8. 10.1038/clpt.1988.107 3391001 source

  • May combine two claims.

    Findingown data

    In a post hoc analysis including only users of snuff, there was no attenuation of the negative regression coefficient between cotinine and total sperm count when adjusting for maternal occupational group, but a 40% reduction in the value of the coefficient when adjusting for maternal smoking.

    “However, in a post hoc analysis, only including users of snuff, but otherwise using the model described above, we could not see an attenuation of a negative regression coefficient between cotinine and total sperm count when adjusting for maternal occupational group, but a 40% reduction in the value of the coefficient when adjusting for maternal smoking.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The fact that we found no statistically significant association between the numbers of boxes of snuff consumed per week and semen parameters might be due to the time of keeping the oral snuff in the mouth varying between individuals, despite potentially consuming the same amount of boxes per week.

    “The fact that we found no statistically significant association between the numbers of boxes of snuff consumed per week and semen parameters might be due to the fact the time of keeping the oral snuff in the mouth may vary between different individuals, despite potentially consuming the same amount of boxes per week.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The association between snuff use and total sperm count seemed to lie in the same direction as associations between cotinine levels in urine and total sperm count, which seems to strengthen the possibility of causality.

    “The fact that the association between the use of snuff and total sperm count seemed to lie in the same direction as associations between the levels of cotinine in urine and total sperm count (as an additional way of evaluating the association between the use of snuff and semen quality) seems to strengthen the possibility of causality.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Another rat study showed a dose-response relationship between nicotine and impaired sperm parameters and fertility, and that ceasing nicotine treatment improved the sperm parameters.

    “Another rat study showed a dose–response relationship between nicotine and impaired sperm parameters and fertility, and that ceasing nicotine treatment improved the sperm parameters. 10”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [10] Oyeyipo IP, Raji Y, Emikpe BO, Bolarinwa AF. Effects of nicotine on sperm characteristics and fertility profile in adult male rats: A possible role of cessation. J Reprod Infertil. 2011; 12(3): 201‐ 7. 23926503 PMC3719292

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Several variables were only available in part of the men, such as the numbers of boxes of snuff used per week and maternal occupational field.

    “Weaknesses of our study include the fact that several variables were only available in part of the men, such as the numbers of boxes of snuff used per week, maternal occupational field, etc.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    Cotinine was analysed using liquid chromatography tandem mass spectrometry with a limit of detection of 0.4 ng/ml and a coefficient of variation of 2% at 48 ng/ml, as part of a quality control program.

    “Cotinine was analysed in the urine samples from 396 of the men, using liquid chromatography tandem mass spectrometry (LC–MS/MS; QTRAP5500, AB Sciex, Framingham, MA, USA) with a modified serum method 20 , 21 at the Division of Occupational and Environmental Medicine at Lund University. The limit of detection was 0.4 ng/ml, and the coefficient of variation at 48 ng/ml was 2%. The analysis of cotinin”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [20] Axelsson J, Rylander L, Rignell‐Hydbom A, Lindh CH, Jonsson BA, Giwercman A. Prenatal phthalate exposure and reproductive function in young men. Environ Res. 2015; 138C: 264‐ 270. 10.1016/j.envres.2015.02.024 25743932 source
    • cites [21] Axelsson J, Sabra S, Rylander L, Rignell‐Hydbom A, Lindh CH, Giwercman A. Association between paternal smoking at the time of pregnancy and the semen quality in sons. PLoS One. 2018; 13(11): e0207221. 10.1371/journal.pone.0207221 30462692 PMC6248964 source

      Checked before — its earlier verdict is held back until a new check runs.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    The data collection and study were approved by the local ethical review board at Lund University and were in line with the Declaration of Helsinki.

    “The data collection and study of associations between exposure and reproductive function were approved (approval number 181/2008) by the local ethical review board at Lund University, and was in line with the Declaration of Helsinki.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    That may increase the likelihood of the results being representative of the population.

    “That may increase the likelihood of the results being representative of the population.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    Adjusting for maternal occupational field changed the cotinine-total sperm count coefficient 36% versus zero, and for maternal smoking 38% in the same direction.

    “When instead adjusting for maternal occupational field, this changed the coefficient 36% versus zero, and for maternal smoking 38% in the same direction.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    The findings on snuff use and sperm cells, cotinine and testosterone/oestradiol, and boxes of snuff and testosterone/FSH were robust to additional adjustment for use of alcohol, long-term/chronic diseases, varicocele, maternal occupational group, and maternal and paternal smoking during pregnancy.

    “All of these findings seemed robust to additional adjustment for use of alcohol, long‐term/chronic diseases, varicocele, maternal occupational group, and maternal and paternal smoking during the pregnancy.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    These results seem to be in line with snuff use being associated with a lower total sperm count, potentially dose-relatedly.

    “As such, these results seem to be in line with snuff use to be associated with a lower total sperm count, potentially dose‐relatedly.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The separate additional adjustments for boxes of snuff per week gave less than a 3% lowering of the regression coefficients.

    “The separate additional adjustments gave less than a 3% lowering of the regression coefficients.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    We can still not exclude that other factors related to the use of snuff or exposure to nicotine may have been playing a role for the associations with sperm count and reproductive hormones in the men included in this study.

    “Nonetheless, we can still not exclude that other factors related to the use of snuff or exposure to nicotine may have been playing a role for the associations with sperm count and reproductive hormones in the men included in this study.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    For statistically significant findings, additional separate adjustments for long-term chronic diseases, varicocele, alcohol use, maternal occupational field, and maternal and paternal smoking were performed to reduce confounding.

    “For statistically significant findings, to try to reduce the possibility of confounding, we adjusted separately also for either (1) long‐term chronic diseases (26 men yes, 491 men no, missing in 6 men); (2) varicocele (only available for the last recruited cohort; 26 yes, 267 no); (3) alcohol use latest week (available in 290 men [all from the last recruited cohort] with a mean of 5.8 glasses”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductown data

    The analyses were adjusted for cigarette smoking and time of abstinence for semen parameters, and for smoking and cohort for hormones.

    “We used general linear models, with adjustments including cigarette smoking, and for semen parameters also abstinence time.”
    • Also stated in: § Hormone levels · plain
      “The analyses were adjusted for both cigarette smoking [yes/no] and the time of abstinence (missing in 18 men), since they both can influence semen quality. 28”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999; 84(10): 3666‐ 72. 10.1210/jcem.84.10.6079 10523012 source

  • May combine two claims.

    Interpretationcitation

    With the difference we found of 34 million sperms between the groups, the chance of fathering a child for those who used snuff should thus equal 0.97^3.4 times that of the non-users, which equals a 9.8% decreased chance of fathering a child in the users of snuff, with a potential dose-related association.

    “With the difference we found of 34 million sperms between the groups, the chance of fathering a child for those who used snuff should thus equal 0.97 3 . 4 times that of the non‐users. That would equal 9.8% decreased chance of fathering a child in the users of snuff, with a potential dose‐related association.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductcitation

    Sperm concentration, semen volume, total sperm count, percent morphologically normal and progressively motile sperm were analysed according to WHO guidelines, and DNA fragmentation index was studied by the Sperm Chromatin Structure Assay.

    “Sperm concentration (millions/ml), semen volume (ml), total sperm count (millions of sperms), percent morphologically normal sperms (%) and percent progressively motile sperms (%) were analysed according to the WHO guidelines used at the time. 22 Furthermore, the sperm DNA fragmentation index was studied by use of the Sperm Chromatin Structure Assay, 23 as previously briefly described for the two”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [22] Organisation mondiale de la s. WHO laboratory manual for the examination of human semen and sperm‐cervical mucus interaction. Cambridge: Cambridge University Press; 1999.

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [23] Evenson DP. Sperm chromatin structure assay (SCSA(R)). Methods Mol Biol. 2013; 927: 147‐ 64. 10.1007/978-1-62703-038-0_14 22992911

      Not checked in the free run.

    • cites [24] Axelsson J, Rylander L, Rignell‐Hydbom A, Silfver KA, Stenqvist A, Giwercman A. The impact of paternal and maternal smoking on semen quality of adolescent men. PLoS One. 2013; 8(6): e66766. 10.1371/journal.pone.0066766 PONE‐D‐13‐03305 [pii] 23840528 PMC3694111 source

      Checked before — its earlier verdict is held back until a new check runs.

26 of 26

  • The paper relies on this without support.

    There is a reported association between sperm count and the chance of pregnancy such that a 24% lower sperm count corresponds to about a 10% lower chance of fathering a child.

    “Applying these results to a reported association between sperm count and the chance of pregnancy, men who used snuff would have about a 10% lower chance of fathering a child.”
1 of 1

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?

  • Previous studies have shown that smokers have significantly higher levels of TST and EST than non-smokers.

    “previous studies have shown that smokers have significantly higher levels of TST and EST than non-smokers [16–19]”

    From Associations between smoking, sex steroid hormones, trouble sleeping, and depression among U.S. adults: a cross-sectional study from NHANES (2013–2016) (2024) · cites this paper as [17]

    The Results table (page not available) reports significantly higher testosterone in snuff users than non-users, but it does not compare smokers with non-smokers; the oestradiol difference between snuff groups was not significant (P = 0.19). The Discussion reports a significant positive association of urinary cotinine with both hormones, which lends partial support to the hormone association but does not establish the claimed smoker-versus-non-smoker comparison. (LLM, conf=0.83)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • More chronic-disease cases in Table 1 than in the reported data

    Minor

    The methods report 26 men with a long-term or chronic disease, but Table 1 lists 9 snuff users and 19 non-users with one, totaling 28. These two groups cannot contain more cases than the reported dataset.

  • Cotinine-sperm-count P value differs between text and table

    Minor

    The Results text reports P = 0.03 for the negative association between cotinine and total sperm count, while the corresponding Table 4 row reports P = 0.02.

  • Table 1 exceeds the reported number with alcohol-use data

    Minor

    The methods say alcohol-use data were available for 290 men, whereas Table 1 lists 65 snuff users and 237 non-users with alcohol-use data, totaling 302.

  • Regression coefficient falls outside its reported confidence interval

    Minor

    For progressively motile sperm in Table 4, the coefficient is 0.12 × 10−3, but the reported 95% confidence interval ends at 0.012 × 10−3. A point estimate cannot lie outside its own confidence interval.

4 of 4

Cites

Flagged first, then by citations

Research works printed but not linked: 5

  1. Services USDoHaH, 2016, E‐Cigarette Use Among Youth and Young Adults: A Report of the Surgeon General
  2. 10.1111/j.1365‐2605.2007.00752.x · DOI · Paper page
  3. 10.1093/humrep/der045 · DOI
  4. 1999, Organisation mondiale de la s. WHO laboratory manual for the examination of human semen and sperm‐cervical mucus interaction
  5. World Health O, 2010, WHO Laboratory Manual for the Examination and Processing of Human Semen

Cited by

Sorted by citations

Related

Authors
Kimblad, A., Ollvik, G., Lindh, C. H., & Axelsson, J.
Affiliations
Lund University (SE)
Corresponding author
Axelsson, Jonatan
ORCID
Venue
Andrology
Publisher
Wiley
Published
2022-06-08
Volume
10
Issue
6
Pages
1181-1188
ISSN
  • 2047-2919 (ISSN-L)
  • 2047-2927
DOI
10.1111/andr.13198
PMC
PMC9543234
OpenAlex
W4281644740
Cited by
11
References
33
Citations by year
2026: 4 · 2025: 1 · 2024: 5 · 2023: 1
FWCI
1.43
Type
journal article
Language
en
Open access
Licence
Locations
  • Andrology (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Lund University Publications (Lund University) (submittedVersion)
Funders
Svenska Läkaresällskapet
Topics
  • Health Sciences › Medicine › Reproductive Medicine › Sperm and Testicular Function
  • Health Sciences › Medicine › Physiology › Smoking Behavior and Cessation
  • Health Sciences › Medicine › Pediatrics, Perinatology and Child Health › Prenatal Substance Exposure Effects
Keywords
oral snuff, smokeless tobacco, sperm count, semen quality, testosterone, estradiol, follicle-stimulating hormone, cotinine, nicotine exposure, sperm DNA fragmentation, male fertility, reproductive hormones
MeSH terms
Cotinine, Humans, Male, Sperm Count, Sweden, Testosterone, Tobacco, Smokeless

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.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-11-05.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-11-05.

Cited sources are checked by gpt-6-sol.

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 ›

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