Risk Of Multiple Sclerosis Relapse Research Articles

Cell-Mediated Immunity in Multiple Sclerosis Patients Who Discontinued Therapy with an Integrin Inhibitor

Introduction. Natalizumab (NTZ) is a humanized monoclonal antibody (mAb) that selectively inhibits α4-integrin adhesion molecule located on the surface of lymphocytes and prevents their trafficking into the central nervous system (CNS).
 The aim of this study was to identify characteristics of lymphocyte population and subpopulation pattern in the peripheral blood (PB) of multiple sclerosis (MS) patients who discontinued NTZ due to an increased risk of developing developing progressive multifocal leukoencephalopathy.
 Materials and methods. We conducted an open-label prospective observational study in 26 MS patients. Of those, 6 patients had rapidly progressive MS, 10 patients discontinued NTZ and had confirmed relapses afterwards, and 10 patients received NTZ and had no relapses during the washout period. Ten apparently healthy individuals were used as controls. Cell-mediated immunity parameters were evaluated by flow cytometry using a panel of mAbs to differentiation antigens of PB lymphocytes.
 Results. Patients who discontinued NTZ had significantly decreased absolute lymphocyte counts in PB, decreased T-cytotoxic, NKT and B1 lymphocyte subpopulation levels, and decreased activated T-cell (CD3+HLA–DR+) levels, which may be related to their redistribution, passing through the blood-brain barrier, and trafficking into the central nervous system. CD20+ В-cell levels did not differ from normal. Additional immune predictors of MS relapses after NTZ discontinuation can include decreased absolute count of PB lymphocytes and decreased percentage of CD3+CD8+ T-cell, NKT-cell, and B1-cell (CD19+CD5+) subpopulations. Significantly increased levels of CD25+- and CD38+-activated B-cells compared with the normal levels in naïve patients and subjects without relapses after NTZ discontinuation may suggest a high activation potential of the circulating B-cell pool and, therefore, a high risk of MS relapses.
 Conclusions. The changes in the lymphocyte subpopulation pattern in the PB of MS patients after NTZ discontinuation may have a prognostic value for assessing the risk of relapses; they justified switching patients to anti-B-cell therapy.

Association between active and passive smoking and the clinical course of multiple sclerosis and neuromyelitis optica spectrum disorder

<i>Objective</i>: Active and passive smoking are common environmental risk factors, but there is no definite conclusion about their effects on relapse and disability progression in multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). <i>Methods</i>: This was a retrospective cohort study. Patients were included from four centers. Demographic and clinical data were extracted from the clinical database, while data involving environmental exposures during daily life, relapse, and disability progression were obtained through telephone follow-up interviews. Determinants of relapse were assessed by Cox proportional models, and disability progression was assessed by linear regression. Kaplan‒Meier survival was used to estimate relapse within five years after the first attack. <i>Results</i>: A total of 130 MS patients and 318 NMOSD patients were included in this study, and females accounted for 60% and 79.6%, respectively. MS patients with an active smoking history had a higher risk of relapse, for which the association became borderline significant after accounting for covariates (aHR=1.52, 95% CI=1.00, 2.31; <i>p</i>=0.052). The relapse risk between ever-smokers who smoked more than 10 cigarettes per day and smokers who smoked less than 10 cigarettes per day was not significantly different (aHR=0.96, 95% CI=0.63, 1.47; <i>p</i>=0.859). However, exposure to passive smoking was associated with a reduced risk of MS relapse (aHR=0.75, 95% CI=0.56, 1.00; <i>p</i>=0.044) compared with never-exposed patients. No associations were observed between active smoking/passive smoking and the risk of NMOSD relapse, but patients with a history of smoking were associated with a lower annual progression rate by Expanded Disability Status Scale (EDSS) (aβ=−0.20, 95% CI=−0.38, −0.01; <i>p</i>=0.036) and Multiple Sclerosis Severity Score (MSSS) (aβ=−0.23, 95% CI=−0.44, −0.03; <i>p</i>=0.028). <i>Conclusion</i>: Our research shows that active smoking increases the relapse risk of MS and has a negative impact on disability progression; thus, smoking cessation should be encouraged.

Cerebrospinal Fluid Chloride Is Associated with Disease Activity of Relapsing-Remitting Multiple Sclerosis: A Retrospective Cohort Study.

Blood-brain barrier dysfunction in active multiple sclerosis (MS) lesions leads to pathological changes in the cerebrospinal fluid (CSF). This study aimed to investigate the possible association between routine CSF findings, especially CSF chloride, at the time of the first lumbar puncture and the relapse risk and disability progression of relapsing-remitting MS (RRMS). This retrospective study included 77 patients with RRMS at the MS Center of our institution from January 2012 to December 2020. The Anderson and Gill (AG) model and Spearman correlation analysis were used to explore predictors of relapse and disability during follow-up. In the multivariate AG model, patients with elevated CSF chloride level (hazard ratio [HR], 1.1; 95% confidence interval [CI]: 1.06-1.22; p = 0.001) had a high risk of MS relapse. Using median values of CSF chloride (123.2 mmol/L) as a cut-off, patients with CSF chloride level ≥ 123.2 mmol/L had a 120% increased relapse risk compared with those with CSF chloride level < 123.2 mmol/L (HR = 2.20; 95% CI: 1.19-4.05; p = 0.012). Elevated CSF chloride levels might be a biologically unfavorable predictive factor for disease relapse in RRMS.

Saudi Consensus Recommendations on the Management of Multiple Sclerosis: Disease-Modifying Therapies and Management of Relapses

For the past 10 years, disease-modifying therapy (DMT) options for multiple sclerosis (MS) have grown remarkably where DMTs have been shown to reduce the risk of MS relapses. MS patients are advised to begin treatment with a DMT shortly after diagnosis to limit the possibility of disease progression over time. While patients with radiologically isolated syndrome do not require pharmacologic treatment, high-risk patients with clinically isolated syndrome are advised to start DMTs. This article provides evidence-based recommendations for DMT use in MS management, helping healthcare practitioners advise patients on treatment decisions. We aim to provide recommendations for the management of acute MS relapses. The recommendations herein were developed following the gathering of a panel of experts after evaluating international guidelines, and the latest evidence was collected through a comprehensive literature review.

Neutrophil-to-lymphocyte ratio and monocyte-to-lymphocyte ratio are associated with a 2-year relapse in patients with multiple sclerosis

BackgroundThe association between increased neutrophil-to-lymphocyte ratio (NLR) and multiple sclerosis has been demonstrated in several studies. The monocyte-to-lymphocyte ratio (MLR) is an emerging biomarker for disease monitoring. Moreover, there has not been a published Taiwanese study to date. AimTo investigate the correlation of NLR, MLR and white blood cell (WBC) count as possible biomarkers for predicting a 2-year relapse in patients with multiple sclerosis (MS). Materials and methodsA total of 641 Taiwanese patients with MS were enrolled in the present study between January 1, 2001, and December 31, 2018. We collected data on NLR, MLR, WBC count, disease-modifying therapy (DMT) use, and the time between first diagnosis and first relapse in all patients within a 2-year duration. ResultsIn the relapse group, there were significantly more patients with NLR >median or MLR >median (p = 0.006 and p = 0.020, respectively). There were also more patients with WBC count >median, although the difference was not statically significant (p = 0.069). The adjusted hazard ratio for relapse and NLR >median was 1.61(p = 0.008). The adjusted hazard ratio for relapse and MLR >median was 1.43 (p = 0.044). Patients with NLR >median or MLR >median had a significantly (p = 0.008 and p = 0.039, respectively) increased risk of MS relapse in the 2 years, compared with those who had NLR <median or MLR <median. ConclusionNLR and MLR are widely available, fast and measurable inflammatory markers for predicting the relapse risk of MS patients.

Risk of multiple sclerosis relapses when switching from fingolimod to cell-depleting agents: the role of washout duration.

Fingolimod (FTY) induces sequestration of lymphocytes in secondary lymphoid organs and the average lymphocyte recovery following discontinuation takes 1-2months. It has been hypothesized that the therapeutic effects of subsequent cell-depleting agents may be compromised if initiated before lymphocyte recovery has occurred. To assess the risk of relapses following FTY discontinuation and the initiation of a B/T cell-depleting agent in relation to washout duration using data from the Italian MS Register. The risk of relapses was assessed in relation to different washout durations (< 6, 6-11, 12-17 and > / = 18weeks) in patients starting alemtuzumab, rituximab, ocrelizumab or cladribine following FTY discontinuation. We included 329 patients in the analysis (226F, 103M; mean age 41 ± 10years). During the cell-depleting treatment, the incidence rate ratio for a relapse was significantly greater in patients with a washout period of 12-17 and > / = 18weeks compared to the reference period (< 6weeks). The risk of a relapse was significantly influenced by the occurrence of relapses during FTY treatment and by washout length, with hazard ratios markedly increasing with the washout duration. The risk of relapses increases with the washout duration when switching from FTY to lymphocyte-depleting agents.

Multiple Sclerosis, Disease-Modifying Therapies and COVID-19: A Systematic Review on Immune Response and Vaccination Recommendations.

Understanding the risks of COVID-19 in patients with Multiple Sclerosis (MS) receiving disease-modifying therapies (DMTs) and their immune reactions is vital to analyze vaccine response dynamics. A systematic review on COVID-19 course and outcomes in patients receiving different DMTs was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Emerging data on SARS-CoV-2 vaccines was used to elaborate recommendations. Data from 4417 patients suggest that MS per se do not portend a higher risk of severe COVID-19. As for the general population, advanced age, comorbidities, and higher disability significantly impact COVID-19 outcomes. Most DMTs have a negligible influence on COVID-19 incidence and outcome, while for those causing severe lymphopenia and hypogammaglobulinemia, such as anti-CD20 therapies, there might be a tendency of increased hospitalization, worse outcomes and a higher risk of re-infection. Blunted immune responses have been reported for many DMTs, with vaccination implications. Clinical evidence does not support an increased risk of MS relapse or vaccination failure, but vaccination timing needs to be individually tailored. For cladribine and alemtuzumab, it is recommended to wait 3–6 months after the last cycle until vaccination. For the general anti-CD20 therapies, vaccination must be deferred toward the end of the cycle and the next dose administered at least 4–6 weeks after completing vaccination. Serological status after vaccination is highly encouraged. Growing clinical evidence and continuous surveillance are extremely important to continue guiding future treatment strategies and vaccination protocols.

Assessing environmental epidemiology questions in practice with a causal inference pipeline: An investigation of the air pollution‐multiple sclerosis relapses relationship

When addressing environmental health-related questions, most often, only observational data are collected for ethical or practical reasons. However, the lack of randomized exposure often prevents the comparison of similar groups of exposed and unexposed units. This design barrier leads the environmental epidemiology field to mainly estimate associations between environmental exposures and health outcomes. A recently developed causal inference pipeline was developed to guide researchers interested in estimating the effects of plausible hypothetical interventions for policy recommendations. This article illustrates how this multistaged pipeline can help environmental epidemiologists reconstruct and analyze hypothetical randomized experiments by investigating whether an air pollution reduction intervention decreases the risk of multiple sclerosis relapses in Alsace region, France. The epidemiology literature reports conflicted findings on the relationship between air pollution and multiple sclerosis. Some studies found significant associations, whereas others did not. Two case-crossover studies reported significant associations between the risk of multiple sclerosis relapses and the exposure to air pollutants in the Alsace region. We use the same study population as these epidemiological studies to illustrate how appealing this causal inference approach is to estimate the effects of hypothetical, but plausible, environmental interventions.

Pregnancy and Multiple Sclerosis: An Update on the Disease Modifying Treatment Strategy and a Review of Pregnancy's Impact on Disease Activity.

Pregnancy rates are rapidly increasing among women of reproductive age diagnosed with multiple sclerosis (MS). Through pre-conception, pregnancy and post-partum periods, there is a need for disease control management, to decrease chances of MS relapses while avoiding potential risks to the mother and the fetus. However, pregnancy is not always compatible with the available highly effective MS treatments. This narrative review provides the aspects of pregnancy’s outcomes and the impact on disease activity, choices of anesthesia and the management of relapses during the pregnancy and breastfeeding period. Available disease modifying treatment is discussed in the article with new data supporting the strategy of continuing natalizumab after conception, as it is related to a decreased risk of MS relapses during the pregnancy and postpartum period.

Sex effects across the lifespan in women with multiple sclerosis

Multiple sclerosis (MS) is an autoimmune inflammatory demyelinating central nervous system disorder that is more common in women, with onset often during reproductive years. The female:male sex ratio of MS rose in several regions over the last century, suggesting a possible sex by environmental interaction increasing MS risk in women. Since many with MS are in their childbearing years, family planning, including contraceptive and disease-modifying therapy (DMT) counselling, are important aspects of MS care in women. While some DMTs are likely harmful to the developing fetus, others can be used shortly before or until pregnancy is confirmed. Overall, pregnancy decreases risk of MS relapses, whereas relapse risk may increase postpartum, although pregnancy does not appear to be harmful for long-term prognosis of MS. However, ovarian aging may contribute to disability progression in women with MS. Here, we review sex effects across the lifespan in women with MS, including the effect of sex on MS susceptibility, effects of pregnancy on MS disease activity, and management strategies around pregnancy, including risks associated with DMT use before and during pregnancy, and while breastfeeding. We also review reproductive aging and sexual dysfunction in women with MS.

Genetic variation in the gene LRP2 increases relapse risk in multiple sclerosis

BackgroundDue to the lack of prospective studies with longitudinal data on relapse, past genetic studies have not attempted to identify genetic factors that predict relapse risk (the primary endpoint of...

Exclusive Breastfeeding and the Effect on Postpartum Multiple Sclerosis Relapses.

Women with multiple sclerosis (MS) experience an elevated risk of relapse after giving birth. The effect of exclusive breastfeeding on postpartum risk of MS relapse is unclear. To determine the effect of exclusive breastfeeding on postpartum risk of MS relapse and to investigate the effect of introducing supplemental feedings on that risk. Data on 201 pregnant women with relapsing-remitting MS were collected prospectively from January 1, 2008, to June 30, 2012, with 1 year follow-up post partum in the nationwide German MS and pregnancy registry. The effect of the intention to breastfeed exclusively (no regular replacement of breastfeeding meals with supplemental feedings) for at least 2 months compared with nonexclusive breastfeeding (partial or no breastfeeding) on the first postpartum MS relapse, using Cox proportional hazards regression model adjusted for age and disease activity, before and during pregnancy was analyzed. Data analysis was performed from August 30, 2013, to May 25, 2015. Exclusive breastfeeding defined as at least 2 months of breastfeeding without regular replacement of any meal by supplemental feeding. First postpartum MS relapse. Of 201 women, 120 (59.7%) intended to breastfeed exclusively for at least 2 months and 81 (40.3%) breastfed and included supplemental feeding (42 [20.9%]) or did not breastfeed (39 [19.4%]). Thirty-one women (38.3%) who did not breastfeed exclusively had a relapse within the first 6 months post partum compared with 29 women (24.2%) who intended to breastfeed exclusively for at least 2 months (unadjusted hazard ratio, 1.80; 95% CI, 1.09-2.99; P = .02; adjusted hazard ratio, 1.70; 95% CI, 1.02-2.85; P = .04). The time to first postpartum relapse after the introduction of supplemental feedings did not differ significantly between women who previously breastfed exclusively and those who did not (P = .60). The findings of this study suggest that exclusive breastfeeding is a modestly effective MS treatment with a natural end date. Our study provides further evidence that women with MS who breastfeed exclusively should be supported to do so since it does not increase the risk of postpartum relapse.

Disease relapses in multiple sclerosis can be influenced by air pollution and climate seasonal conditions.

Environmental factors may influence the disease activity in patients with relapsing-remitting multiple sclerosis (MS). The aim of this study was to evaluate the in- fluence of air pollution and seasonal climate factors of any on number of relapses in MS patients during a consecutive 5 years of observation. We retrospectively analyzed data of MS patients from the town of Niš, hospitalized at the Clinic of Neurology, Clinical Center Niš, Serbia, from 2005 to 2009. Climate data: mean daily sun shining; mean monthly sun shining, mean whole daily cloudiness, daily cloudiness at 7 a.m, 2 p.m. and 9 p.m. and air pollution expressed by NSR (New Source Review) were obtained from the Meteorology Observatory Niš. During a 5-year of observation there were 260 relapses in 101 MS patients. The number of relapses showed a significantly negative correlation with the number of days with NSR < 2 (p = -0.31; p < 0.01) and a positive correlation with the mean whole daily cloudiness (p < 0.05), mean daily cloudiness at 7 a.m. (p < 0.05) and 2 p.m. (p < 0.01). We found a significantlly positive correlation (p < 0.05) between the reduced number of relapses during the period of high vitamin D season, i.e. July-October. There was a statistically significant increase (p < 0.01) of the number of relapses during spring (x = 6.53; SD = 3.98) compared to the other three seasons. The joint presence of lower number of days with NSR < 2 during low vitamin D season (January- April) correlated with a statistically significant increase of the number of relapses in MS patients (F = 5.06, p < 0.01). CON- CLUSION: The obtained results confirmed the influence of air pollution and climate seasonal conditions on disease relapses in MS patients based on a long-term observation. Lower numbers of days with low air pollution during the periods with low vitamin D (January-April), especially with increased cloudiness at 2 p.m, induce a higher risk of MS relapses in southern continental parts of Europe.

Genetic variation in PBMC-produced IFN-γ and TNF-α associations with relapse in multiple sclerosis

BackgroundAlterations in peripheral blood mononuclear cell (PBMC) cytokine production have been found in multiple sclerosis (MS) compared to healthy controls. We have previously found that stimulated PBMC-produced TNF-α and IFN-γ modulated MS relapse risk, such that raised TNF-α was protective, while raised IFN-γ increased relapse risk. ObjectiveTo assess whether SNPs within genes for relevant cytokines and their receptors modulate the associations of TNF-α and IFN-γ with relapse, thus providing additional information about these cytokine effects and the roles of these genes in MS. MethodsProspective cohort of 91 participants with relapsing–remitting MS and cytokine and genotype data. SNPs (N=361) within a window of 10kb around each cytokine/cytokine receptor gene (N=84) were selected for analysis. Predictors of PBMC cytokines were evaluated by multilevel mixed-effects linear regression. Predictors of relapse were evaluated by Cox proportional hazards regression. Bonferroni correction was used to adjust for multiple testing; thus p<1.39×10−4 was defined as significant. ResultsIndividuals of GG genotype of rs3218295 (within the gene IL2RB) demonstrated a significant protective effect of TNF-α on relapse while those of GA/AA genotype showed a significant positive association (pinteraction=5.04×10−5). Carriers of CC genotype of rs522807 (3′ region of TNFRSF1B) and the AA genotype of rs25879 (5′ region of IL3) showed a strong association between IFN-γ and increased relapse risk (pinteraction=8.21×10−5 and 1.70×10−5, respectively). ConclusionsOur results show novel modulation of TNF-α and IFN-γ associations with relapse by SNPs in major cytokines. These findings suggest the potential for these genes and/or their products as potential therapeutic targets in MS.

The vitamin D controversy – Part 2

Vitamin D has been implicated to play a role in multiple sclerosis (MS) since several reports showed that low vitamin D levels might increase the risk of MS and may contribute to disease progression. Vitamin D has been reported to regulate expression of the cytokine interleukin (IL)-17 which can play a key role in MS pathogenesis. Immunological effects of vitamin D administration have been explored in a few normal subjects could not be replicated with certainty in MS patients. This could be explained by vitamin D interaction with other components that modify MS such as seasonal variation, concomitant infection with EBV, estrogen signalling system, and therapy-induced changes in vitamin D metabolism. The utility of vitamin D level as a serological marker for disease activity has been assessed in several studies but the results were suboptimal due to small number of patients enrolled, and lack of correlation of vitamin D levels with MS symptomatology. Similarly, the results of several studies assessing vitamin D supplementation were inconclusive. A recent meta-analysis revealed no significant association between high-dose vitamin D treatment and risk of MS relapses. The lack of supportive evidence could be due to methodological factors including the starting time of supplementation during disease course, vitamin D doses and formulation, inclusion of patients with minimal disease activity, duration of the study, and concomitant use of disease modifying therapies. Hence, despite the observational evidence of the effect of vitamin D on MS course, there is a lack of high quality, large, randomized trials investigating whether vitamin D supplementation benefits people with MS.

Stimulated PBMC-produced IFN-γ and TNF-α are associated with altered relapse risk in multiple sclerosis: results from a prospective cohort study

BackgroundAltered reactivity of peripheral blood mononuclear cells (PBMC) and their production of cytokines may affect multiple sclerosis (MS) clinical course. We assessed the relationship of stimulated PBMC-produced IFN-γ, TNF-α, IL-4...

MS disease activity in RESTORE

Objective:RESTORE was a randomized, partially placebo-controlled exploratory study evaluating multiple sclerosis (MS) disease activity during a 24-week interruption of natalizumab.Methods:Eligible patients were relapse-free through the prior year on natalizumab and had no gadolinium-enhancing lesions on screening brain MRI. Patients were randomized 1:1:2 to continue natalizumab, to switch to placebo, or to receive alternative immunomodulatory therapy (other therapies: IM interferon β-1a [IM IFN-β-1a], glatiramer acetate [GA], or methylprednisolone [MP]). During the 24-week randomized treatment period, patients underwent clinical and MRI assessments every 4 weeks.Results:Patients (n = 175) were randomized to natalizumab (n = 45), placebo (n = 42), or other therapies (n = 88: IM IFN-β-1a, n = 17; GA, n = 17; MP, n = 54). Of 167 patients evaluable for efficacy, 49 (29%) had MRI disease activity recurrence: 0/45 (0%) natalizumab, 19/41 (46%) placebo, 1/14 (7%) IM IFN-β-1a, 8/15 (53%) GA, and 21/52 (40%) MP. Relapse occurred in 4% of natalizumab patients and in 15%–29% of patients in the other treatment arms. MRI disease activity recurred starting at 12 weeks (n = 3 at week 12) while relapses were reported as early as 4–8 weeks (n = 2 in weeks 4–8) after the last natalizumab dose. Overall, 50/167 patients (30%), all in placebo or other-therapies groups, restarted natalizumab early because of disease activity.Conclusions:MRI and clinical disease activity recurred in some patients during natalizumab interruption, despite use of other therapies.Classification of evidence:This study provides Class II evidence that for patients with MS taking natalizumab who are relapse-free for 1 year, stopping natalizumab increases the risk of MS relapse or MRI disease activity as compared with continuing natalizumab.

Adverse lipid profile is not associated with relapse risk in MS: Results from an observational cohort study

BackgroundThere is increasing evidence that serum lipids and apolipoproteins may be associated with multiple sclerosis (MS) clinical course. ObjectiveTo investigate the associations between serum lipids, apolipoproteins, body mass index and relapse in MS. MethodsA prospective cohort of 141 participants with relapsing–remitting MS was followed from 2002 to 2005. Serum lipid and apolipoprotein levels were measured biannually, and body mass index at baseline. The association with hazard of relapse was assessed using survival analysis. ResultsNeither body mass index nor any of the lipid-related measures were associated with the hazard of relapse. ConclusionSerum lipid profile and body mass index are not associated with the hazard of relapse in MS.

Multiple Sclerosis and Pregnancy

Multiple sclerosis (MS) is a chronic neurological illness affecting adults at the time when they are most likely to consider starting a family. It is known that the risk of MS relapse declines during pregnancy but increases in the first 3 to 6 months postpartum. It is also known that this risk is not affected by delivery method, anesthesia type, or parity. Unanswered questions remain, including long-term pregnancy effects on MS outcomes, effects of lactation on postpartum relapses, or the best management strategies of MS patients through reproductive cycle. This review provides information and guidelines for counseling patients with MS desiring motherhood.

The effect of vitamin D-related interventions on multiple sclerosis relapses: a meta-analysis

Observational studies have shown an association between lower vitamin D levels and higher risk of relapse among people with multiple sclerosis (MS). This has raised interest in potential clinical benefits of vitamin D supplementation in the management of MS. The objectives were to examine the effect of vitamin D based interventions on the relative risk of relapse in MS. Any randomised controlled trial assessing the effect on the relative risk of relapse of any formulation or dose of vitamin D, in participants with MS, was eligible. The inverse variance with random effects model in Review Manager 5.1 was used to calculate the odds ratio of relapses in high dose vitamin D treated patients vs. controls. Five studies were published as of September 2012, yielding a total of 129 high-dose vitamin D-treated patients and 125 controls. We found no significant association between high-dose vitamin D treatment and risk of MS relapse (OR 0.98, 95% CI 0.45–2.16). In conclusion, although no significant association between high-dose vitamin D treatment and risk of MS relapses was found, the studies were limited by several methodological limitations. Further larger, more prolonged studies are merited.