Healthy Brazilian Population Research Articles

Parâmetros de referência espaço-temporais de um sensor inercial para sujeitos brasileiros sadios

Gait analysis in a laboratory may be expensive, time-consuming, and restricted to a controlled environment. Validated wearable technology may be an alternative to such analysis. However, wearable technologies should demonstrate reference values of a healthy population. Objective: To establish spatio-temporal gait reference values of an accelerometer (G-Walk) in a healthy Brazilian population. Methods: This is a cross-sectional study with 124 healthy subjects evaluated with G-Walk in the 6-minute and 10-meter walk tests (6MWT and 10MWT). Gait parameters of Velocity, Cadence, Distance, and gait symmetry variables were retrieved for analysis. Clinical and demographical characteristics were also collected and tested with simple linear regression as covariables of the gait characteristics. The bootstrapped 5th percentile of the gait parameter established the reference values. If a covariable influence was found, the reference values were established by subgroup analysis according to the covariable. Results: The study analyzed 114 subjects, mostly women (67.74%), aged 39.36 (SD 12.18). Height was a covariable of cadence for the 10MWT and cadence and stride length for the 6MWT. Age and sex combined were covariables of 6MWT velocity, and sex alone was a covariable of 6MWT. All reference values for symmetry were above 89%, velocity at the 10MWT was above 1.0m/s, and distance at the 6MWT was 354m and 359.5 for females and males, respectively. Conclusions: Our study generated reference values for spatio-temporal gait analysis with G-Walk of a population of a major urban area, considering the covariables of age, height, and sex.

PB1191 Prevalence of Anti-PF4 Antibodies in a Healthy Brazilian Population after Immunization with AstraZeneca Vaccine

PB1191 Prevalence of Anti-PF4 Antibodies in a Healthy Brazilian Population after Immunization with AstraZeneca Vaccine

BNT162b2 mRNA COVID-19 against symptomatic Omicron infection following a mass vaccination campaign in southern Brazil: A prospective test-negative design study

BackgroundEvidence regarding effectiveness of BNT162b2 mRNA COVID-19 vaccine against Omicron in Latin America is limited. We estimated BNT162b2 effectiveness against symptomatic COVID-19 in Brazil when Omicron was predominant. MethodsThis prospective test-negative, case-control study was conducted in Toledo, Brazil, following a mass COVID-19 vaccination with BNT162b2. Patients were included if they were aged ≥12 years, sought care for acute respiratory symptoms in the public health system between November 3, 2021 and June 20, 2022, and were tested for SARS-CoV-2 using RT-PCR. In the primary analysis, we determined the effectiveness of two doses of BNT162b2 against symptomatic COVID-19. ResultsA total of 4,574 were enrolled; of these, 1,758 patients (586 cases and 1,172 controls) were included in the primary analysis. Mean age was 27.7 years, 53.8 % were women, and 90.1 % had a Charlson comorbidity index of zero. Omicron accounted for >97 % of all identified SARS-CoV-2 variants, with BA.1 and BA.2 accounting for 84.3 % and 12.6 %, respectively. Overall adjusted estimate of two-dose vaccine effectiveness against symptomatic COVID-19 was 46.7 % (95 %CI, 19.9 %–64.6 %) after a median time between the second dose and the beginning of COVID-19 symptoms of 94 days (IQR, 60–139 days). Effectiveness waned from 77.7 % at 7–29 days after receipt of a second dose to <30 % (non-significant) after ≥120 days. ConclusionIn a relatively young and healthy Brazilian population, two doses of BNT162b2 provided protection against symptomatic Omicron infection. However, this protection waned significantly over time, underscoring the need for boosting with variant-adapted vaccines in this population prior to waves of disease activity.Trial registration number:ClinicalTrials.gov number, NCT05052307 (https://clinicaltrials.gov/ct2/show/NCT05052307).

Determining Percentiles of Atherosclerotic Cardiovascular Risk According to Sex and Age in a Healthy Brazilian Population.

Expressing the risk of atherosclerotic cardiovascular disease (ASCVD) as percentiles of the distribution according to sex and age may provide a better perception of the risk. To determine percentiles of the 10-year ASCVD risk distribution according to sex and age in a sample of the Brazilian population; to characterize individuals at low 10-year risk but high risk percentile. We analyzed individuals aged 40 to 75 years who underwent routine health evaluations from 2010 to 2020. Persons with known clinical ASCVD, diabetes mellitus, chronic kidney disease, or LDL-cholesterol ≥ 190 mg/dL were excluded. The 10-year ASCVD risk was calculated by the ACC/AHA pooled cohort equations. Local polynomial regression was used to determine risk percentiles. Two-sided p-values < 0.050 were considered statistically significant. Our sample comprised 54,145 visits (72% male, median age [interquartile range] 48 [43, 53] years). We constructed sex-specific graphs plotting age against ASCVD risk corresponding to the 10th, 25th, 50th, 75th, and 90th percentiles. Most males up to 47 years and females up to 59 years above the 75th percentile had a 10-year risk < 5%. Individuals at low 10-year risk and risk percentile ≥ 75th had a high prevalence of excess weight and median (interquartile range) LDL-cholesterol levels 136 (109, 158) mg/dL (males) and 126 (105, 147) mg/dL (females). We established ASCVD risk percentiles according to sex and age in a large sample of the Brazilian population. This approach may increase risk awareness and help identify younger persons at low 10-year risk who may benefit from more aggressive risk factor control.

MO573: Diet Quality Components and Gut Microbiota of Peritoneal Dialysis Patients

Abstract BACKGROUND AND AIMS Diet has been recognized as an important determinant of microbiota composition. In CKD, nutrients such as fiber and protein have been shown to influence the microbiota profile. However, since nutrients are not ingested in isolation, the overall assessment of diet, reflecting the synergy of nutrients, may potentially modify the relationship between the diet and gut microbiota. Therefore, our aim was to evaluate whether the quality of diet and its components associate with alpha diversity of gut microbiota and phyla composition in peritoneal dialysis (PD) patients. METHOD In this cross-sectional study, patients undergoing automated PD for at least 3 months, aged 18–75 years and clinically stable were enrolled. Those who were using prebiotics, probiotics, symbiotics and antibiotics within a period of 30 days before the study were not included. Participants received sterile materials to collect the feces sample and were instructed to keep it refrigerated and bring to the clinic within a period of 12 h. To evaluate α-diversity and phyla microbial profile, 16S ribosomal DNA was PCR-amplified and sequenced on an IlluminaMiSeq platform. The diet quality index (DQI), validated for the healthy Brazilian population, was calculated from a 3-day food record. This index is based on the energy density of 11 components (sugars and sweets; beef and pork; refined grains and breads; animal fat; poultry, seafood and eggs; whole grains, breads, tubers and roots; fruits; non-starchy vegetables; legumes and nuts; milk and dairy products and vegetable oils). Each component is scored from 0 to 5 or 10, and a final score ranged from 0 (worse) to 100 (better) is obtained. RESULTS Thirty-seven patients were included [52.4 ± 13.7 years; 54% men; 70% with diabetes; PD vintage 18.0 (5.0–46.5) months]. The distribution of gut microbiota's phyla is presented in Figure 1. Mean DQI was 47.8 ± 12.2, indicating that most of the patients (76%) were in an intermediate quality of diet. DQI was not associated with age, gender, PD vintage, BMI or the presence of diabetes. As can be seen in Table 1, although no association was found between DQI total score with the gut microbiota α-diversity indexes, the energy density of some components of DQI tended or was associated with those indexes. DQI total score was also not associated with any specific phyla, but the energy density of the components ‘sugars and sweets’ was negatively associated with Bacteroidetes (r= −0.389, P = 0.017) and positively with Firmicutes (r = 0.468, P = 0.003), while the inverse was observed for ‘legumes and nuts’, Bacteroidetes (r = 0.358, P = 0.029) and Firmicutes (r = −0.333, P = 0.044). CONCLUSION A healthier diet, with a larger amount of ‘whole grains, breads, tubers and roots’ and ‘legumes and nuts’ and, lower in ‘sugars and sweets’, seems to contribute to the α-diversity or Bacteroidetes colonization in peritoneal dialysis patients.

Evaluation of the Cutaneous Silent Period in a Healthy Brazilian Population.

To establish cutaneous silent period (CSP) normative values and investigate the variables that may influence them. We tested 41 healthy subjects. All subjects underwent nerve conduction studies, and we evaluated the CSP in both arms. Four subjects did not have CSP and were excluded. The analyses were performed in the healthy group composed of 23 women and 14 men, with a mean age of 35 (range, 19-64) years. The CSP median duration was 23.2 milliseconds (ms), with 2 to 98th percentile at 11.3 and 48.7 ms. The median onset latency was 87.9 (range, 72.9-109) ms, and the median end latency was 112 (range, 93.8-138) ms. The CSP onset latency positively correlated with height, whereas CSP end latency and duration were weakly but significantly associated with age. Some measurements of ulnar nerve conduction study also correlated with CSP measures. The interrater coefficients for the primary measures of onset and end latency demonstrates the reproducibility of the method. The CSP with the fifth digit stimulation and recording from the abductor digiti minimi muscle is a valid diagnostic tool that can be used in clinical practice.

Predictive equations for ventilatory muscle strength in the Brazilian population: a systematic review

ABSTRACT Maximal inspiratory and expiratory pressures (MIP and MEP) assess the strength index of the respiratory muscles. These measures are relevant to assess respiratory muscle strength and for clinical monitoring. This study evaluates papers that suggest predictive equations of MIP and MEP for the Brazilian population. We included studies that established prediction equations for MIP and MEP for the healthy Brazilian population, aged from 4 to 90 years old, both men and women and that had the maximum respiratory pressures measured in a sitting position. A search was carried out in March 2020 on MEDLINE, LILACS, Cochrane, SciELO, CINAHL, Web of Science, and SCOPUS databases, without date or language filters. The descriptors used were “muscle strength,” “equations,” “predictive respiratory muscles” and their respective synonyms. Out of the 3,920 studies found in databases, 963 were duplicates, 2,779 were excluded, 178 had their full texts analyzed, and only 9 met the inclusion criteria. The predictive equations of ventilatory muscle strength analyzed in this review used age, weight, and stature as variables. However, the studies showed methodological weaknesses, such as lack of cross-validation of the equation, exclusion of outliers, and lack of familiarization of MIP and MEP.

Facial anthropometric analysis of a healthy group of young Brazilian adults by means of stereophotogrammetry technique

Abstract Introduction: Anthropometry is the science responsible for measuring the weight, size, and proportions of the human body, providing valuable and objective insights into how to characterize phenotypic variation and dysmorphology. Among the newer methods for facial analysis, the stereophotogrammetry technique has shown excellent results given its use of a group of fast cameras that photograph subjects from multiple angles. Objective: The aims of the present study were: (1) to analyze the facial profile of a group of healthy young Brazilian adults, between 18 and 30 years of age, (2) to define common facial values among the subjects, (3) to create a database of facial measurements of a portion of this young healthy Brazilian population to be used in future works, and (4) to test the precision and repeatability of the Vectra M3® equipment. Material and method: Sixty healthy young Brazilian adults participated in the study, 30 males and 30 females. Temporary craniometrical landmarks were performed in soft tissue, and those subjects underwent image capturing by the stereophotogrammetry technique. Thirty landmarks were used to take the measurements (in mm) of 35 distances. The equipment repeatability was tested in 20% of the sample (i.e., 12 subjects). Result: The values between the first and second acquisitions were statistically (p&lt;0.05) similar for all 35 distances analyzed. The findings allowed the creation of a reliable database containing facial distances of a portion of the young healthy Brazilian population. In addition, the distances Tr-N, N-Sn, Ls-Sto, Sto-Li, En[r]-En[l] and Prn-Sn were not statistically different for the group of men (GM) and the group of women (GW), while the other 29 distances were significantly greater in GM. Conclusion: The technique and methods employed in the study yielded objective analyses of the facial profile of this group of healthy young Brazilian adults, and the equipment Vectra M3® showed a high level of precision and repeatability.

Obesity and metabolic phenotypes (metabolically healthy and unhealthy variants) are significantly associated with prevalence of elevated C-reactive protein and hepatic steatosis in a large healthy Brazilian population.

Background. Among the obese, the so-called metabolically healthy obese (MHO) phenotype is thought to confer a lower CVD risk as compared to obesity with typical associated metabolic changes. The present study aims to determine the relationship of different subtypes of obesity with inflammatory-cardiometabolic abnormalities. Methods. We evaluated 5,519 healthy, Brazilian subjects (43 ± 10 years, 78% males), free of known cardiovascular disease. Those with <2 metabolic risk factors (MRF) were considered metabolically healthy, and those with BMI ≥ 25 kg/m2 and/or waist circumference meeting NCEP criteria for metabolic syndrome as overweight/obese (OW). High sensitivity C reactive protein (hsCRP) was measured to assess underlying inflammation and hepatic steatosis (HS) was determined via abdominal ultrasound. Results. Overall, 40% of OW individuals were metabolically healthy, and 12% normal-weight had ≥2 MRF. The prevalence of elevated CRP (≥3 mg/dL) and HS in MHO versus normal weight metabolically healthy group was 22% versus 12%, and 40% versus 8% respectively (P < 0.001). Both MHO individuals and metabolically unhealthy normal weight (MUNW) phenotypes were associated with elevated hsCRP and HS. Conclusion. Our study suggests that MHO and MUNW phenotypes may not be benign and physicians should strive to treat individuals in these subgroups to reverse these conditions.

Evidence of a protective lipid profile in the presence of c.+83C>T SNP in apolipoprotein A-I gene in a healthy Brazilian population

Evidence of a protective lipid profile in the presence of c.+83C>T SNP in apolipoprotein A-I gene in a healthy Brazilian population

Afericoes e exames clinicos realizados nos participantes do ELSA-Brasil

The article describes assessments and measurements performed in the Brazilian Longitudinal Study for Adult Health (ELSA-Brasil). Some assessments including anthropometric assessment, casual blood pressure measurement, and ankle-brachial index have an established clinical application while others including pulse wave velocity, heart rate variability, and carotid intima-media thickness have no established application and do not have reference values for healthy Brazilian population but may be important predictors of cardiovascular outcomes. Blood pressure measurement following postural change maneuver was included in the ELSA-Brasil because it has not been much tested in epidemiological studies. Innovative approaches were developed for assessing the ankle-brachial index using an automatic device instead of the mercury column to measure blood pressure and for assessing the anterior-posterior diameter of the right lobe of the liver by ultrasound for quantitative assessment of nonalcoholic fatty liver disease. All ELSA-Brasil subjects were younger (35 years or more) than those included in other cohorts studying subclinical atherosclerosis. The inclusion of younger individuals and a variety of assessments make the ELSA-Brasil a relevant epidemiology study nationwide and worldwide.

Determination of reference interval values for inorganic elements in whole blood samples of humans and laboratory animals by X-ray fluorescence spectrometry

Inorganic elements are responsible for essential bodily functions, such as osmotic regulation, cardiac frequency and contractibility, blood clotting and neuromuscular excitability. The determination of inorganic elements in corporeal fluids such as blood, serum, plasma and urine is used as a monitor for a part or the whole organism; their values, then, are compared with reference interval values. In this study, the energy dispersive X-ray fluorescence spectrometry (EDXRF), applying the Fundamental Parameters method, for the determination of inorganic elements in whole blood samples from humans and laboratory animals, was used. Peripheral blood samples were collected and, before coagulation, 100 μL of sample were deposited onto Whatman No. 41 filter paper and dried, using infrared spotlight. The reference interval values for healthy Brazilian population of Na were found to be 1,788–1,826 μg g−1, of Mg 63–75 μg g−1, of P 602–676 μg g−1, of S 1,519–1,718 μg g−1, of Cl 2,743–2,867 μg g−1, of K 1,508–1,630 μg g−1, of Ca 214–228 μg g−1, of Fe 170–184 μg g−1, of Cu 4–6 μg g−1 and of Zn 1–3 μg g−1. The reference interval values for golden hamster (Mesocricetus auratus) of Na were found to be 1,714–1,819 μg g−1, Mg 51–79 μg g−1, P 970–1,080 μg g−1, S 1,231–1,739 μg g−1, Cl 2,775–2,865 μg g−1, of K 1,968–2,248 μg g−1, of Ca 209–257 μg g−1, of Fe 145–267 μg g−1, of Cu 4–6 μg g−1 and of Zn 3–5 μg g−1. A comparative study between EDXRF and instrumental neutron activation analysis data was carried out and the results for both techniques are statistically equal (α = 0.05). The results contribute for the establishment of reference interval values for Na, Mg, P, S, Cl, K, Ca, Cu and Zn in the healthy Brazilian population and the referred laboratory animal species.

Cross-cultural adaptation and psychometric properties of the Brazilian-Portuguese version of the VSP-A (Vécu et Santé Perçue de l'Adolescent), a health-related quality of life (HRQoL) instrument for adolescents, in a healthy Brazilian population

BackgroundHealth-related quality of life (HRQoL) assessment, encompassing the adolescents' perceptions of their mental, physical, and social health and well-being is increasingly considered an important outcome to be used to identify population health needs and to provide targeted medical care. Although validated instruments are essential for accurately assessing HRQoL outcomes, there are few cross-culturally adapted tools for use in Brazil, and none designed exclusively for use among adolescents. The Vécu et Santé Perçue de l'Adolescent (VSP-A) is a generic, multidimensional self-reported instrument originally developed and validated in France that evaluates HRQoL of ill and healthy adolescents.PurposeTo cross-culturally adapt and validate the Brazilian-Portuguese version of the VSP-A, a generic HRQoL measure for adolescents originally developed in France.MethodsThe VSP-A was translated following a well-validated forward-backward process leading to the Brazilian version. The psychometric evaluation was conducted in a sample of 446 adolescents (14-18 years) attending 2 public high schools of São Gonçalo City. The adolescents self-reported the Brazilian VSP-A, the validated Psychosomatic Symptom Checklist and socio-demographic information. A retest evaluation was carried out on a sub-sample (n = 195) at a two-week interval.The internal construct validity was assessed through confirmatory factor analysis (CFA), multi-trait scaling analyses, Rasch analysis evaluating unidimensionality of each scale and Cronbach's alpha coefficients. The reproducibility was evaluated by intra-class correlation coefficients (ICC). Zumbo's ordinal logistic regression analysis was used to detect differential item functioning (DIF) between the Brazilian and the French items. External construct validity was investigated testing expected differences between groups using one-way analysis of variance (ANOVA), Mann-Whitney tests and the univariate general regression linear model.ResultsCFA showed an acceptable fit (RMSEA=0.05; CFI=0.93); 94% of scaling success was found for item-internal consistency and 98% for item discriminant validity. The items showed good fit to the Rasch model except 3 items with an INFIT at the upper threshold. Cronbach's Alpha ranged from 0.60 to 0.85. Test-retest reliability was moderate to good (ICC=0.55-0.82). DIF was evidenced in 4 out of 36 items. Expected patterns of differences were confirmed with significantly lower physical, psychological well being and vitality reported by symptomatic adolescents.ConclusionsAlthough DIF in few items and responsiveness must be further explored, the Brazilian version of VSP-A demonstrated an acceptable validity and reliability in adolescents attending school and might serve as a starting point for more specific clinical investigations.

Vitamin D status in a sunny country: Where has the sun gone?

Hypovitaminosis D [serum 25 vitamin D<30 ng/ml] is related to the development of metabolic bone disease and greater risk of chronic illnesses. However, it is frequently under-diagnosed, mainly in countries where UV radiation is abundant. We prospectively determined the prevalence and the predictors of serum 25 vitamin D (s25(OH)D) in a healthy Brazilian population after the winter and after the summer. 603 (118M and 485F) healthy Brazilian volunteers aged 18-90 years from a universitary hospital were selected after the winter of 2006. From the initial sample, 209 volunteers (31M and 178F) accepted to participate in a second health check after the subsequent summer. After the winter, median s25(OH)D was 21.4 ng/mL and 77.4% of the population presented hypovitaminosis D. s25(OH)D was significantly related to age, BMI, PTH and race. In multivariate linear regression analysis, s25(OH)D was significantly and independently dependent on age, glycemia and skin color. Significant increase in s25(OH)D was verified after summer [10.6 (3.7-19.3 ng/ml); p<0.001] and this improvement was dependent on age. We also observed a significant decrease in hyperparathyroidism prevalence (20.8% vs. 4.9%; P<0.0001). In São Paulo, at the end of winter, we observed a high prevalence of hypovitaminosis D and secondary hyperparathyroidism in healthy adults. s25(OH)D was dependent on age and skin color. After summer, we observed a decrease in the prevalence of hypovitaminosis D. This unexpected finding emphasizes the need for a strong recommendation to monitor s25(OH)D, even in a sunny country such as Brazil.

Antidesmoglein 1 reactivity in a healthy Brazilian population at low risk for endemic pemphigus foliaceus (fogo selvagem)

Antidesmoglein 1 reactivity in a healthy Brazilian population at low risk for endemic pemphigus foliaceus (fogo selvagem)

Lower heart rate variability is associated with higher serum high-sensitivity C-reactive protein concentration in healthy individuals aged 46 years or more

Background To test the hypothesis of an association between cardiac autonomic activity evaluated by heart rate variability and systemic inflammatory markers such as C-reactive protein, we studied the correlation of the indices of heart rate variability relative to serum high-sensitivity C-reactive protein (hs-CRP) in a healthy Brazilian population. Methods Four hundred twenty-one healthy individuals aged 15–82 years (mean 40.4 years), 184 men (43.7%) and 237 women (56.3%) were enrolled between July 1998 and July 2001. The relationship between the log-transformed indices of the heart rate variability and the serum concentration of hs-CRP were analyzed stratified by age tertile using the Spearman correlation coefficient and multiple linear regression. Results The log standard deviation of all normal sinus RR intervals over 24 h (SDNN) ( r = − 0.801; p = 0.024) was independently correlated with log hs-CRP in the individuals with age in the oldest tertile (≥ 46 years). In addition, the body mass index (BMI) was independently correlated with hs-CRP in all of the age groups. Conclusions In the healthy subjects aged 46 years or more the lower heart rate variability correlated with higher concentration of hs-CRP.

High-sensitivity C-reactive protein concentration in a healthy Brazilian population

Background: The use of serum high-sensitivity C-reactive protein (hs-CRP) for cardiovascular risk profiling requires knowledge of the distribution in different populations. We studied serum hs-CRP in a healthy Brazilian population, with no evidence of heart disease, relative to gender and smoking status as well as other clinical and laboratory variables. Methods: 684 healthy Brazilian individuals, aged 14–74 years (mean 40.6 years), 295 men (43.1%) and 389 women (56.9%), were enrolled between July 1998 and July 2001. The relationship between the log-transformed hs-CRP, stratified by gender and smoking status (non-smokers, smokers), and clinical and laboratory variables were analyzed using the Spearman correlation coefficient and multiple linear regression. Results: In a multiple linear regression model age ( β=1.0069, p=0.03), body mass index (BMI) ( β=1.0093, p<0.01), total cholesterol/HDL cholesterol ratio (TC/HDL-C) ( β=1.1015, p<0.01) and heart rate ( β=1.0139, p<0.01) were independently correlated with hs-CRP. Stratification according to gender and smoking was able to disclose different interactions between these variables and hs-CRP. Variables significantly correlated in each stratum were as follows: in smoker men, age ( β=1.0236, p=0.04) and TC/HDL-C ( β=1.2065, p<0.01); in non-smoker men, BMI ( β=1.0786, p<0.01) and TC/HDL-C (β=1.1397, p=0.01); in smoker women, BMI ( β=1.1006, p=0.03); and in non-smoker women, BMI ( β=1.0873, p<0.01), TC/HDL-C ( β=1.1405, p=0.01) and heart rate ( β=1.0165, p=0.02). Conclusions: The clinical and laboratory variables studied influenced the concentration of hs-CRP according to gender and smoking. In assessing the risk of cardiovascular events in relation to serum hs-CRP level, stratification by gender and smoking status is indicated.

Glutathione S-transferase Mu (GSTM1) null genotype in relation to gender, age and smoking status in a healthy Brazilian population

The glutathione S-transferase mu (GSTM1) gene which acts during phase II of xenobiotic metabolism is polymorphic in the population, being absent in about 30-50% of individuals depending on the ethnic group from which they come. Epidemiological studies suggest that individuals who are homozygous null at the GSTM1 locus may have an increased risk of developing various types of neoplastic disease. We used the polymerase chain reaction (PCR) to estimate the frequency of GSTM1 in 176 healthy individuals from the north of Parana (Brazilian state), the null genotype being detected in 48.86% of these individuals. The Student’s t-test was used to evaluate the frequency of the glutathione S-transferase null genotype in relation to age, gender and smoking habit and no significant differences were found. In our sample there were 142 individuals of Caucasian origin, of which 47.88% had the null genotype. When applied to the Caucasian group only (n = 142) the Student’s t-test again showed no significant differences between the frequency of the GSTM1 null genotype and age, gender and smoking habit.