Skip to main content
Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Toxoplasma gondii infection and insomnia: A case control seroprevalence study

  • Cosme Alvarado-Esquivel ,

    Roles Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Writing – original draft

    alvaradocosme@yahoo.com

    Affiliation Biomedical Research Laboratory, Faculty of Medicine and Nutrition, Juárez University of Durango State, Durango, Mexico

  • Sergio Estrada-Martínez,

    Roles Data curation, Formal analysis, Software

    Affiliation Institute for Scientific Research “Dr. Roberto Rivera-Damm”, Juárez University of Durango State, Durango, Mexico

  • Alma Rosa Pérez-Álamos,

    Roles Data curation, Formal analysis, Software

    Affiliation Institute for Scientific Research “Dr. Roberto Rivera-Damm”, Juárez University of Durango State, Durango, Mexico

  • Agar Ramos-Nevárez,

    Roles Data curation, Investigation

    Affiliation Clínica de Medicina Familiar, Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado, Durango, Mexico

  • Karina Botello-Calderón,

    Roles Formal analysis

    Affiliation Biomedical Research Laboratory, Faculty of Medicine and Nutrition, Juárez University of Durango State, Durango, Mexico

  • Ángel Osvaldo Alvarado-Félix,

    Roles Formal analysis

    Affiliation Biomedical Research Laboratory, Faculty of Medicine and Nutrition, Juárez University of Durango State, Durango, Mexico

  • Raquel Vaquera-Enríquez,

    Roles Data curation, Methodology

    Affiliation Health Center No. 2 “Dr. Carlos Santamaría”, Servicios de Salud de Durango, Durango, Durango, Mexico

  • Gustavo Alexis Alvarado-Félix,

    Roles Formal analysis

    Affiliation Biomedical Research Laboratory, Faculty of Medicine and Nutrition, Juárez University of Durango State, Durango, Mexico

  • Antonio Sifuentes-Álvarez,

    Roles Methodology

    Affiliation Biomedical Research Laboratory, Faculty of Medicine and Nutrition, Juárez University of Durango State, Durango, Mexico

  • Carlos Alberto Guido-Arreola,

    Roles Data curation, Investigation

    Affiliation Clínica de Medicina Familiar, Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado, Durango, Mexico

  • Elizabeth Rábago-Sánchez,

    Roles Conceptualization, Methodology

    Affiliation Biomedical Research Laboratory, Faculty of Medicine and Nutrition, Juárez University of Durango State, Durango, Mexico

  • Leandro Saenz-Soto

    Roles Data curation, Investigation

    Affiliation Clínica de Medicina Familiar, Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado, Durango, Mexico

Abstract

We determined the association between Toxoplasma gondii (T. gondii) infection and insomnia. Through an age-and gender-matched case-control study, 577 people with insomnia (cases) and 577 people without insomnia (controls) were tested for anti-T. gondii IgG and IgM antibodies using commercially available enzyme-immunoassays. Anti-T. gondii IgG antibodies were found in 71 (12.3%) of 577 individuals with insomnia and in 46 (8.0%) of 577 controls (OR = 1.62; 95% CI: 1.09–2.39; P = 0.01). Men with insomnia had a higher (16/73: 21.9%) seroprevalence of T. gondii infection than men without insomnia (5/73: 6.8%) (OR: 3.81; 95% CI: 1.31–11.06; P = 0.009). The rate of high (>150 IU/ml) anti-T. gondii IgG antibody levels in cases was higher than the one in controls (OR = 2.21; 95% CI: 1.13–4.31; P = 0.01). Men with insomnia had a higher (8/73: 11.0%) rate of high anti-T. gondii IgG antibody levels than men without insomnia (0/73: 0.0%) (P = 0.006). The rate of high anti-T. gondii IgG antibody levels in cases >50 years old (11/180: 6.1%) was higher than that (3/180: 1.7%) in controls of the same age group (OR: 3.84; 95% CI: 1.05–14.00; P = 0.05). No difference in the rate of IgM seropositivity between cases and controls was found (OR = 1.33; 95% CI: 0.57–3.11; P = 0.50). Results of this seroepidemiology study suggest that infection with T. gondii is associated with insomnia. Men older than 50 years with T. gondii exposure might be prone to insomnia. Further research to confirm the association between seropositivity and serointensity to T. gondii and insomnia is needed.

Introduction

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite [1]. Toxoplasmosis, the disease caused by T. gondii, is a zoonosis with medical and veterinary importance worldwide [2]. T. gondii infects one third of the global human population [3]. Foodborne transmission of T. gondii in humans occurs mainly by eating undercooked meat, especially pork, lamb, and wild game meat from T. gondii-infected animals, and ingestion of raw fruits and vegetables contaminated with soil containing cat feces [4]. Transmission of T. gondii may also occur by blood transfusion, tissue transplants, or ingestion of unpasteurized milk [5]. In addition, T. gondii can be transmitted vertically during pregnancy [6]. Infections with T. gondii may result in a clinical spectrum ranging from a completely asymptomatic infection to multi-organ involvement [7]. Some patients with toxoplasmosis present cervical lymphadenopathy or ocular disease, whereas a reactivation of latent disease in immunocompromised patients can cause life-threatening encephalitis [8]. Chronic toxoplasmosis might be associated with a vast array of neuropsychiatric symptoms [9]. Seroprevalence of T. gondii infection has been linked to mixed anxiety and depressive disorder [10], schizophrenia [11, 12], depression [13, 14], and suicide behavior [14, 15]. Few studies have shown a link between T. gondii infection and insomnia. However, results of such studies are controversial. In a study of students, a positive association between seropositivity to T. gondii and insomnia was found in women but not in men [16]. In two further studies, researchers found that T. gondii IgG seropositivity and serointensity were not associated with insomnia [17, 18]. T. gondii can disseminate to brain in infected hosts [3], and we hypothesize that T. gondii can involve brain structures related with sleep leading to sleep problems as insomnia. Several neurotransmitters are involved in sleep including for instance, dopamine and gamma-aminobutyric acid (GABA) [19], and T. gondii infections impact on these two neurotransmitters. T. gondii infections alter the dopamine metabolism [20], and GABAergic synapses and signaling in the central nervous system [21]. Therefore, this study was aimed to determine the association between T. gondii exposure and insomnia in a sample of people in Durango, Mexico.

Materials and methods

Study design and study population

Through an age- and gender-matched case-control study, 577 people with insomnia (cases) and 577 people without insomnia (controls) were examined for the presence of T. gondii exposure. This study was performed in the northern Mexican state of Durango from 2014 to 2019. Cases and controls were individuals attending public health care institutions for medical consultations or laboratory tests. Inclusion criteria for cases were people with insomnia, aged ≥18 years, with informed consent. Gender, occupation, and socioeconomic status were not restrictive criteria for enrollment of cases or controls. The Diagnostic and Statistical Manual of Mental Disorders, Fifth edition (DSM-5) defines insomnia as a predominant complain of dissatisfaction with sleep quantity or quality, associated with one (or more) of the following symptoms: difficulty initiating sleep, difficulty maintaining sleep, and early-morning awakening with inability to return to sleep [22]. Inclusion criteria for enrollment of controls were people without insomnia, aged ≥18 years, with informed consent. Of the 577 cases, 505 (87.5%) were women and 72 (12.5%) were men. They were 18–80 years old (mean: 43.63 ± 12.55). Whereas of the 577 controls, 503 (87.2%) were women and 74 (12.8%) were men. They were 18–81 years old (mean: 43.63 ± 12.56). There were no differences in age (P = 0.99) or gender (P = 0.93) among cases and controls.

Laboratory tests

Five ml of venous blood was drawn from each participant. After blood clotting, blood samples were centrifuged. Serum was transferred into microtubes and kept at -20°C until assayed. All samples were analyzed for anti-T. gondii IgG antibodies using the commercially available enzyme-linked immunoassay “Toxoplasma gondii IgG” kit (Diagnostic Automation/Cortez Diagnostics, Inc., Woodland Hills, California. USA). This test allows detection and quantification of anti-T. gondii IgG antibodies. A cut-off of 8 IU/ml was used to determine seropositivity. Samples with results just below 8 IU/ml (grey zone) or clearly lower were considered as negatives. Serum samples with anti-T. gondii IgG antibodies were further analyzed for detection of anti-T. gondii IgM antibodies by the commercially available enzyme-linked immunoassay “Toxoplasma gondii IgM” kit (Diagnostic Automation/Cortez Diagnostics, Inc.). Sera were analyzed every few months during the study period. Positive and negative controls were included in each run. All immunoassays were carried out as described in the manufacturer’s instructions. Laboratory tests were performed blindly, the analyst did not have information about the history of insomnia in participants during the analysis of samples.

Statistical analysis

Data analysis was performed using the software SPSS Statistics version 15. A sample size of 577 cases and 577 controls was calculated using the following parameters: a reference seroprevalence of 6.1% [23] as the expected frequency of exposure in controls, a two-sided confidence level of 95%, a power of 90%, a 1:1 proportion of cases and controls, and an odds ratio of 2.0. The student’s t-test was used to assess age matching. To compare the frequencies among the groups the Pearson’s chi-square test or the Fisher’s exact test (when a value was below 5) were used. Multivariate analysis with adjustment by age, sex, education, and residence to further assess the association between T. gondii infection and insomnia was performed. Odd ratios (OR) and corresponding 95% confidence intervals (CI) were calculated. A statistical P value of ≤ 0.05 was considered significant for all comparisons.

Ethical aspects

The Ethical Committees of the Institute of Security and Social Services for the State Workers and the General Hospital of the Secretary of Health in Durango City, Mexico approved this project (Approval No. 449/015). A written informed consent from each participant was obtained.

Results

Anti-T. gondii IgG antibodies were found in 71 (12.3%) of 577 individuals with insomnia and in 46 (8.0%) of 577 controls. A statistically significant difference (OR = 1.62; 95% CI: 1.09–2.39; P = 0.01) in anti-T. gondii IgG seroprevalence between cases and controls was found. A stratification by age and sex and seroprevalence of T. gondii infection in individuals with and without insomnia is shown in Table 1. Stratification by sex showed that men with insomnia had a significantly higher (16/73: 21.9%) seroprevalence of T. gondii infection than men without insomnia (5/73: 6.8%) (OR: 3.81; 95% CI: 1.31–11.06; P = 0.009). Whereas stratification by age groups showed that seroprevalence of T. gondii infection in cases was similar to controls regardless their age groups. Of the 71 anti-T. gondii IgG positive cases, 28 (39.4%) had anti-T. gondii IgG antibody levels higher than 150 IU/ml, 6 (8.5%) between 100 IU/ml and 150 IU/ml, and 37 (52.1%) between 8 to 99 IU/ml. On the other hand, of the 46 anti-T. gondii IgG positive controls, 13 (28.2%) had anti-T. gondii IgG antibody levels higher than 150 IU/ml, 5 (10.9%) between 100 IU/ml and 150 IU/ml, and 28 (60.9%) between 8 to 99 IU/ml. A statistically significant difference (OR = 2.21; 95% CI: 1.13–4.31; P = 0.01) in the frequency of individuals with high (>150 IU/ml) anti-T. gondii IgG antibody levels between cases and controls was found. A stratification by sex and age groups and the rates of high (>150 IU/ml) anti-T. gondii IgG antibody levels in cases and controls is shown in Table 2. Stratification by sex showed that men with insomnia had a significantly higher (8/73: 11.0%) rate of high anti-T. gondii IgG antibody levels than men without insomnia (0/73: 0.0%) (P = 0.006). Whereas stratification by age groups showed that the rate of high anti-T. gondii IgG antibody levels in cases >50 years old (11/180: 6.1%) was higher than that (3/180: 1.7%) in controls of the same age group (OR: 3.84; 95% CI: 1.05–14.00; P = 0.05). Multivariate analysis with adjustment by age, sex, education, and residence showed that T. gondii infection was positively associated with insomnia (OR = 1.57; 95% CI: 1.06–2.34; P = 0.02). Of the 71 anti-T. gondii IgG antibody seropositive cases, 21 (29.6%) were also positive for anti-T. gondii IgM antibodies. Whereas, of the 46 anti-T. gondii IgG antibody seropositive controls, 11 (23.9%) were also positive for anti-T. gondii IgM antibodies. No difference in the rate of IgM seropositivity between cases and controls was found (OR = 1.33; 95% CI: 0.57–3.11; P = 0.50).

thumbnail
Table 1. Stratification by sociodemographic variables in cases and controls and IgG seropositivity rates to T. gondii.

https://doi.org/10.1371/journal.pone.0266214.t001

thumbnail
Table 2. Stratification by sex and age in cases and controls and rates of high (≥150 IU/ml) anti-T. gondii IgG antibody levels.

https://doi.org/10.1371/journal.pone.0266214.t002

The dataset of the study that includes all the data used to obtain the results and conclusions of the study is available (S1 File).

Discussion

There are only few studies that have assessed the epidemiological link between T. gondii infection and insomnia. Results of such studies are controversial and there is currently scanty information as to state whether T. gondii exposure leads to insomnia. Therefore, in this age- and gender-matched case-control study we attempted to determine the association between T. gondii exposure and insomnia in a sample of people in the northern Mexican state of Durango. We observed a significantly higher seroprevalence of T. gondii infection in individuals with insomnia than in individuals without insomnia. In addition, we found a significantly higher rate of high anti-T. gondii IgG antibody levels in cases than in controls. Therefore, our results suggest that T. gondii seropositivity and serointensity are positively associated with insomnia. The association between T. gondii infection and insomnia remained significant after multivariable analysis with adjustment for age, sex, education, and residence. However, the association of T. gondii seropositivity and insomnia was observed in men but not in women, and the association between T. gondii serointensity and insomnia was found only in men and in individuals aged >50 years. The positive association between T. gondii seropositivity and insomnia found in our study contrast with that found in a previous study of 200 students in Iran, where investigators observed a positive association between T. gondii seroprevalence and insomnia in women but not in men [16]. It is not clear why the association between seropositivity and insomnia was found only in men in our study. It is unknown whether men are more vulnerable than women to the clinical effects of T. gondii. It is possible that factors associated with T. gondii exposure in men were different from those in women in our study. Further research to determine the association between sociodemographic, clinical, and behavioral factors and T. gondii exposure in men with insomnia is needed. On the other hand, results of our study also contrast with the findings of three more studies. In a study of 311 older adults recruited in a psychiatric institute and clinic in Pittsburg, USA, researchers found no association between insomnia and T. gondii seroprevalence and serointensity [17]. In a study of 2031 Old Order Amish individuals recruited in Lancaster County, USA, researchers found no association between T. gondii seropositivity and serointensity and insomnia [18]. However, a secondary analysis identified, after adjustment by age group, a statistical trend towards shorter sleep duration in seropositive men [18]. In a survey of 833 Old Order Amish participants, T. gondii seropositives reported less sleep problems and less daytime problems due to poor sleep, and higher T. gondii titers were associated with longer sleep duration, earlier bedtime, and earlier mid-sleep time [24]. Difference in the association between T. gondii exposure and insomnia among the studies might be due to differences in the characteristics of the study populations. We studied people enrolled at several health care institutions whereas researchers of other studies enrolled students [16], older adults [17], and Old Order Amish individuals [18, 24]. In addition, there are differences in the sample size and study design among the studies. We used an age- and gender-matched case-control study design and studied 577 cases and 577 controls whereas in another study 180 people suffering from insomnia and 131 normal sleeping participants with no differences in age, gender and race were studied [17]. The study of students was cross-sectional and had 200 participants [16]; and the studies of Old Order Amish were cross-sectional and included between 833 [24] and 2031 participants [18]. Risk factors for T. gondii exposure and host factors might be different among the study populations. In addition, differences in the virulence of T. gondii strains among infected hosts might exist. In an experimental mouse model of chronic T. gondii infection, investigators found that infected mice exhibited chronic sleep–wake alterations over months, including a marked increase in time spent awake [25]. Further research to determine the association between insomnia and T. gondii seropositivity and serointensity are needed. The presence of anti-T. gondii IgM antibody was determined only in anti-T. gondii IgG positive samples. The presence of IgM without IgG is not a reliable result because enzyme immune assays for anti-T. gondii IgM antibodies have high numbers of false-positive results [26]. We did not obtain information about specific sleep variables. Studies to determine an association between T. gondii infection and specific clinical variables of insomnia are needed. We did not screen for neuropsychiatric or neurodegenerative disorders among participants. Further studies with information about sleep clinical variables and the presence of neuropsychiatric or neurodegenerative disorders among participants are needed. Results of our study do not mean that T. gondii infection leads to insomnia. Only longitudinal studies may help to determine the direction of the association.

Conclusions

Results of this age- and gender-matched case-control study suggest that infection with T. gondii is associated with insomnia. Men older than 50 years with T. gondii exposure might be prone to insomnia. Further research to confirm the association between seropositivity and serointensity to T. gondii and insomnia is needed.

Supporting information

References

  1. 1. Robert-Gangneux F, Dardé ML. Epidemiology of and diagnostic strategies for toxoplasmosis. Clin Microbiol Rev. 2012 Apr;25(2):264–96. pmid:22491772
  2. 2. Liu Q, Wang ZD, Huang SY, Zhu XQ. Diagnosis of toxoplasmosis and typing of Toxoplasma gondii. Parasit Vectors. 2015 May 28;8:292. pmid:26017718
  3. 3. Schlüter D, Barragan A. Advances and Challenges in Understanding Cerebral Toxoplasmosis. Front Immunol. 2019 Feb 14;10:242. pmid:30873157
  4. 4. Jones JL, Dubey JP. Foodborne toxoplasmosis. Clin Infect Dis. 2012 Sep;55(6):845–51. pmid:22618566
  5. 5. Tenter AM, Heckeroth AR, Weiss LM. Toxoplasma gondii: from animals to humans. Int J Parasitol. 2000 Nov;30(12–13):1217–58. pmid:11113252
  6. 6. Rajapakse S, Weeratunga P, Rodrigo C, de Silva NL, Fernando SD. Prophylaxis of human toxoplasmosis: a systematic review. Pathog Glob Health. 2017 Oct;111(7):333–342. pmid:28948861
  7. 7. Fabiani S, Pinto B, Bruschi F. Toxoplasmosis and neuropsychiatric diseases: can serological studies establish a clear relationship? Neurol Sci. 2013 Apr;34(4):417–25. pmid:23010876
  8. 8. Montoya JG, Liesenfeld O. Toxoplasmosis. Lancet. 2004 Jun 12;363(9425):1965–76. pmid:15194258
  9. 9. Fuglewicz AJ, Piotrowski P, Stodolak A. Relationship between toxoplasmosis and schizophrenia: A review. Adv Clin Exp Med. 2017 Sep;26(6):1031–1036. pmid:29068607
  10. 10. Alvarado-Esquivel C, Sanchez-Anguiano LF, Hernandez-Tinoco J, Berumen-Segovia LO, Torres-Prieto YE, Estrada-Martinez S, et al. Toxoplasma gondii infection and mixed anxiety and depressive disorder: a case-control seroprevalence study in Durango, Mexico. J Clin Med Res. 2016 Jul;8(7):519–23. pmid:27298660
  11. 11. Stepanova EV, Kondrashin AV, Sergiev VP, Morozova LF, Turbabina NA, Maksimova MS, et al. Toxoplasmosis and mental disorders in the Russian Federation (with special reference to schizophrenia). PLoS One. 2019 Jul 10;14(7):e0219454. pmid:31291336
  12. 12. Alvarado-Esquivel C, Urbina-Álvarez JD, Estrada-Martínez S, Torres-Castorena A, Molotla-de-León G, Liesenfeld O, et al. Toxoplasma gondii infection and schizophrenia: a case control study in a low Toxoplasma seroprevalence Mexican population. Parasitol Int. 2011 Jun;60(2):151–5. pmid:21292026
  13. 13. Alvarado-Esquivel C, Sánchez-Anguiano LF, Hernández-Tinoco J, Berumen-Segovia LO, Torres-Prieto YE, Estrada-Martínez S, et al. Toxoplasma gondii infection and depression: a case-control seroprevalence study. Eur J Microbiol Immunol (Bp). 2016 Apr 25;6(2):85–9. pmid:27429790
  14. 14. Kamal AM, Kamal AM, Abd El-Fatah AS, Rizk MM, Hassan EE. Latent toxoplasmosis is associated with depression and suicidal behavior. Arch Suicide Res. 2020 Nov 9:1–12. pmid:33166476
  15. 15. Alvarado-Esquivel C, Estrada-Martínez S, Ramos-Nevárez A, Pérez-Álamos AR, Beristain-García I, Alvarado-Félix ÁO, et al. Association between Toxoplasma gondii exposure and suicidal behavior in patients attending primary health care clinics. Pathogens. 2021 May 30;10(6):677. pmid:34070892
  16. 16. Khademvatan S, Izadi-Mazidi M, Saki J, Khajeddin N. Mental health and latent toxoplasmosis: comparison of individuals with and without anti-Toxoplasma antibodies. World Health Popul. 2016;17(1):39–46. pmid:28332976
  17. 17. Meshreky KM, Wood J, Chowdari KV, Hall MH, Wilckens KA, Yolken R, et al. Infection with Herpes Simplex virus type 1 (HSV-1) and sleep: The dog that did not bark. Psychiatry Res. 2019 Oct;280:112502. pmid:31382180
  18. 18. Ahmad Z, Moustafa YW, Stiller JW, Pavlovich MA, Raheja UK, Gragnoli C, et al. Sleep onset insomnia, daytime sleepiness and sleep duration in relationship to Toxoplasma gondii IgG seropositivity and serointensity. Pteridines. 2017;28(3–4):195–204. pmid:29657364
  19. 19. Murillo-Rodriguez E, Arias-Carrion O, Zavala-Garcia A, Sarro-Ramirez A, Huitron-Resendiz S, Arankowsky-Sandoval G. Basic sleep mechanisms: an integrative review. Cent Nerv Syst Agents Med Chem. 2012 Mar;12(1):38–54. pmid:22524274
  20. 20. Parlog A, Schlüter D, Dunay IR. Toxoplasma gondii-induced neuronal alterations. Parasite Immunol. 2015 Mar;37(3):159–70. pmid:25376390
  21. 21. Brooks JM, Carrillo GL, Su J, Lindsay DS, Fox MA, Blader IJ. Toxoplasma gondii infections alter GABAergic synapses and signaling in the central nervous system. mBio. 2015 Oct 27;6(6):e01428–15. pmid:26507232
  22. 22. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Arlington: American Psychiatric Publishing; 2013.
  23. 23. Alvarado-Esquivel C, Estrada-Martínez S, Pizarro-Villalobos H, Arce-Quiñones M, Liesenfeld O, Dubey JP. Seroepidemiology of Toxoplasma gondii infection in general population in a northern Mexican city. J Parasitol. 2011 Feb;97(1):40–3. pmid:21348604
  24. 24. Corona CC, Zhang M, Wadhawan A, Daue ML, Groer MW, Dagdag A, et al. Toxoplasma gondii IgG associations with sleep-wake problems, sleep duration and timing. Pteridines. 2019 Feb;30(1):1–9. pmid:30918422
  25. 25. Dupont D, Lin JS, Peyron F, Akaoka H, Wallon M. Chronic Toxoplasma gondii infection and sleep-wake alterations in mice. CNS Neurosci Ther. 2021 Aug;27(8):895–907. pmid:34085752
  26. 26. Liesenfeld O, Press C, Montoya JG, Gill R, Isaac-Renton JL, Hedman K, et al. False-positive results in immunoglobulin M (IgM) toxoplasma antibody tests and importance of confirmatory testing: the Platelia Toxo IgM test. J Clin Microbiol. 1997 Jan;35(1):174–8. pmid:8968902