The role of sex differences in the prevalence and transmission of tuberculosis
Section snippets
Human demography and infectious respiratory disease transmission
In a world where population is growing rapidly, intra-and international labor migration rates are increasing, and some nations are struggling to deal with distorted age structures and highly skewed sex ratios, the role of human demography in infectious disease transmission dynamics is an increasingly pressing question. By modeling the effects of age structure on infectious respiratory disease transmission, for example, Chen et al. were able to conclude that certain cities were more vulnerable
The role of sex ratio in the TB epidemic
The global TB epidemic is characterized by significant differences in prevalence between men and women. That rates of TB are much higher among men than women in large areas of the world has been extensively documented.15 Nevertheless, some scholars believe that these differences are in part, if not wholly, due to the effects of confounding variables such as differential access to care, which would bias case reporting. In this section, we describe the state of the TB epidemic with regard to sex
Critiques of considering of sex ratio in TB prevalence and transmission
In disentangling possible reasons for sex differences in TB rates, we should first ask whether sex differences in TB cases accurately describe the epidemic, or whether they are only an artifact of reporting bias (Martinez et al., 2000). Second, if it can be established that these differences accurately describe existing TB cases, and thus represent real epidemiological differences, it should be investigated whether these differences are biological in nature, or whether they are mediated by
Arguments that observed sex differences represent only reporting bias
Arguments that published sex differences in TB case numbers do not accurately reflect epidemiological trends, but rather represent underreporting, have generally attributed underreporting to two causes: (1) the inability of women in the developing world to access healthcare of the same quality or to the same extent as men, and associated failure to be tested for TB, and (2) failure of existing diagnostics to accurately detect cases among women.17, 20
The majority of discussion surrounding women
Arguments attributing sex differences to confounding with third variables
Confounding factors have been discussed extensively as causes of differences between men and women in TB rates. Two of the most commonly discussed are higher rates of smoking, and of HIV among men, both of which have been associated with TB. The issue of confounding with HIV is addressed by Martinez et al. in their study of TB in San Francisco. As discussed in the previous section, in San Francisco from 1991 to 1996, TB rates were higher among men than women, even in HIV-negative populations.16
Arguments that sex differences only represent differences in disease progression
Related to the argument that TB transmission is modulated by third variables is the idea that such variables modulate not just transmission of TB, but progression from latent to active TB.17 Several studies have suggested that significant sex differences exist in progression from latent TB to active disease. A number of studies in different populations have found that women have higher rates of progression to disease during reproductive years, while men have higher rates of progression to
Conclusions and implications
Based on the evidence presented, we believe that an epidemiological sex bias in TB is a distinct possibility. Whether such a sex bias might be due to biological or cultural factors or both, it would have serious implications in a modern demographic context. While research suggests that a large number of undetected cases of TB among women in the developing world probably exist, the presence of undetected TB among women, is not in itself strong evidence that men and women are equally susceptible
Acknowledgments
This research was supported in part by NSF. The author thanks Professor Marcus W. Feldman for comments on an earlier draft of the manuscript. The corresponding author had full access to all information reviewed in this study and had final responsibility for the decision to submit for publication. The corresponding author was the sole contributor to this manuscript, and has no conflicts of interest to declare.
References (27)
- et al.
Tuberculosis
Lancet
(2011) Gender differentials in tuberculosis: the role of socio-economic and cultural factors
Tubercle and Lung Disease
(1996)- et al.
Do women with tuberculosis have a lower likelihood of getting diagnosed? Prevalence and case detection of sputum smear positive pulmonary TB, a population-based study from Vietnam
Journal of Clinical Epidemiology
(2004) - et al.
Sex, gender, and tuberculosis
The Lancet
(1999) - et al.
Improvement of tuberculosis case detection and reduction of discrepancies between men and women by simple sputum-submission instructions: a pragmatic randomised controlled trial
Lancet
(2007) WHO report 2011: global tuberculosis control
(2011)- et al.
Increasing incidence of fluoroquinolone-resistant Mycobacterium tuberculosis in Mumbai, India
The International Journal of Tuberculosis and Lung Disease: The Official Journal of the International Union Against Tuberculosis and Lung Disease
(2009) - et al.
Drug-resistant tuberculosis in Shanghai, China, 2000–2006: prevalence, trends and risk factors
World Health
(2009) - et al.
Transmission of MDR and XDR tuberculosis in Shanghai, China
PloS One
(2009) - et al.
The effect of demographic and spatial variability on epidemics: a comparison between Beijing, Delhi, and Los Angeles
Construction
(2010)
The impact of realistic age structure in simple models of tuberculosis transmission
PloS One
The effects of artificial gender imbalance. Science & society series on sex and science
EMBO Reports
Skewed sex ratios at birth and future marriage squeeze in China and India, 2005–2100
Demography
Cited by (64)
Characteristics of tuberculosis in Marrakech (Morocco): Epidemiology and related factors
2024, Clinical Epidemiology and Global HealthPossible sex differences in latent tuberculosis infection risk among close tuberculosis contacts
2022, International Journal of Infectious DiseasesCitation Excerpt :This is particularly true in low- and middle-income countries (Horton et al., 2016). While the disproportionate active TB prevalence may be due in part to underreporting in female populations (Saunders et al., 2019), this alone is unlikely to explain such trends, which have been seen in multiple settings (Neyrolles and Quintana-Murci, 2009; Rhines, 2013). Instead, behavioral and physiologic differences have been posited as probable drivers (Nhamoyebonde and Leslie, 2014; Dodd et al., 2016; Horton et al., 2020).
Nutrition in adolescent growth and development
2022, The LancetFrequency of and risk factors for reversion of QuantiFERON test in healthcare workers in an intermediate-tuberculosis-burden country
2021, Clinical Microbiology and InfectionImpact of individual-level factors on Ex vivo mycobacterial growth inhibition: Associations of immune cell phenotype, cytomegalovirus-specific response and sex with immunity following BCG vaccination in humans
2019, TuberculosisCitation Excerpt :Further studies are required to better understand the interplay between CMV-specific response, T-cell activation and NK cells in the context of BCG vaccination. Differences in TB disease notification rates between the sexes are well documented and thought to be a result of biological factors, in addition to social factors [11,14,60]. Therefore, it is of interest that our study demonstrated a higher capacity of BCG-vaccinated females to control mycobacterial growth ex vivo compared to males.