Antiretroviral purchasing and prescription practices in Mexico: constraints, challenges and opportunities

OBJECTIVE

This study examines the antiretroviral (ARV) market characteristics for drugs procured and prescribed to Mexico's Social Protection System in Health beneficiaries between 2008 and 2013, and compares them with international data.

MATERIALS AND METHODS

Procurement information from the National Center for the Prevention and the Control of HIV/AIDS was analyzed to estimate volumes and prices of key ARV. Annual costs were compared with data from the World Health Organization's Global Price Reporting Mechanism for similar countries. Finally, regimens reported in the ARV Drug Management, Logistics and Surveillance System database were reviewed to identify prescription trends and model ARV expenditures until 2018.

RESULTS

Results show that the first-line ARV market is concentrated among a small number of patented treatments, in which prescription is clinically adequate, but which prices are higher than those paid by similar countries. The current set of legal and structural options available to policy makers to bring prices down is extremely limited.

CONCLUSIONS

Different negotiation policies were not successful to decrease ARV high prices in the public health market. The closed list approach had a good impact on prescription quality but was ineffective in reducing prices. The Coordinating Commission for Negotiating the Price of Medicines and other Health Supplies also failed to obtain adequate prices. To maximize purchase efficiency, policy makers should focus on finding long-term legal and political safeguards to counter the high prices imposed by pharmaceutical companies.

Expected population weight and diabetes impact of the 1-peso-per-litre tax to sugar sweetened beverages in Mexico

STUDY QUESTION

What effect on body mass index, obesity and diabetes can we expect from the 1-peso-per-litre tax to sugar sweetened beverages in Mexico?

METHODS

Using recently published estimates of the reductions in beverage purchases due to the tax, we modelled its expected long-term impacts on body mass index (BMI), obesity and diabetes. Microsimulations based on a nationally representative dataset were used to estimate the impact of the tax on BMI and obesity. A Markov population model, built upon an age-period-cohort model of diabetes incidence, was used to estimate the impact on diagnosed diabetes in Mexico. To analyse the potential of tax increases we also modelled a 2-peso-per-litre tax scenario.

STUDY ANSWER AND LIMITATIONS

Ten years after the implementation of the tax, we expect an average reduction of 0.15 kg/m2 per person, which translates into a 2.54% reduction in obesity prevalence. People in the lowest level of socioeconomic status and those between 20 and 35 years of age showed the largest reductions in BMI and overweight and obesity prevalence. Simulations show that by 2030, under the current implementation of 1-peso-per-litre, the tax would prevent 86 to 134 thousand cases of diabetes. Overall, the 2-peso-per-litre scenario is expected to produce twice as much of a reduction. These estimates assume the tax effect on consumption remains stable over time. Sensitivity analyses were conducted to assess the robustness of findings; similar results were obtained with various parameter assumptions and alternative modelling approaches.

WHAT THIS STUDY ADDS

The sugar-sweetened beverages tax in Mexico is expected to produce sizable and sustained reductions in obesity and diabetes. Increasing the tax could produce larger benefits. While encouraging, estimates will need to be updated once data on direct changes in consumption becomes available.

[Satisfaction and perceived quality of people insured by the Social Health Protection in Mexico. Methodological foundations]

Objective:

To describe the conceptual framework and methods for implementation and analysis of the satisfaction survey of the Mexican System for Social Protection in Health.

Materials and methods:

We analyze the methodological elements of the 2013, 2014 and 2015 surveys, including the instrument, sampling method and study design, conceptual framework, and characteristics and indicators of the analysis.

Results:

The survey captures information on perceived quality and satisfaction. Sampling has national and State representation. Simple and composite indicators (index of satisfaction and rate of reported quality problems) are built and described. The analysis is completed using Pareto diagrams, correlation between indicators and association with satisfaction by means of multivariate models.

Conclusions:

The measurement of satisfaction and perceived quality is a complex but necessary process to comply with regulations and to identify strategies for improvement. The described survey presents a design and rigorous analysis focused on its utility for improving.

Recomendaciones para una política nacional de promoción de la lactancia materna en México: postura de la Academia Nacional de Medicina

Para mejorar las prácticas de lactancia materna es necesario fortalecer acciones de promoción, protección y apoyo, y establecer una política nacional multisectorial que incluya elementos indispensables de diseño, implementación, monitoreo y evaluación de programas y políticas públicas, financiamiento para acciones e investigación, desarrollo de abogacía y voluntad política, y promoción de la lactancia materna, todo coordinado por un nivel central. Recientemente, México ha iniciado un proceso de reformas conducentes a la conformación de una Estrategia Nacional de Lactancia Materna (ENLM). Esta estrategia es el resultado de la disponibilidad de evidencia científica sobre los beneficios de la lactancia materna en la salud de la población y el desarrollo de capital humano así como de los datos alarmantes de su deterioro. La implementación integral de una ENLM que incluya el establecimiento de un Comité Nacional Operativo, coordinación intra e intersectorial de acciones, establecimiento de metas claras, monitoreo y penalización de las violaciones al Código Internacional de Comercialización de Sucedáneos de la Leche Materna, y financiamiento de estas acciones es la gran responsabilidad pendiente de la agenda de salud pública del país. 

Dengue vaccine: local decisions, global consequences

As new vaccines against diseases that are prevalent in low- and middle-income countries gradually become available, national health authorities are presented with new regulatory and policy challenges. The use of CYD-TDV – a chimeric tetravalent, live-attenuated dengue vaccine – was recently approved in five countries. Although promising for public health, this vaccine has only partial and heterogeneous efficacy and may have substantial adverse effects. In trials, children who were aged 2–5 years when first given CYD-TDV were seven times more likely to be hospitalized for dengue, in the third year post-vaccination, than their counterparts in the control group. As it has not been clarified whether this adverse effect is only a function of age or is determined by dengue serostatus, doubts have been cast over the long-term safety of this vaccine in seronegative individuals of any age. Any deployment of the vaccine, which should be very cautious and only considered after a rigorous evaluation of the vaccine’s risk–benefit ratio in explicit national and subnational scenarios, needs to be followed by a long-term assessment of the vaccine’s effects. Furthermore, any implementation of dengue vaccines must not weaken the political and financial support of preventive measures that can simultaneously limit the impacts of dengue and several other mosquito-borne pathogens.

Chikungunya Virus as Cause of Febrile Illness Outbreak, Chiapas, Mexico, 2014

Since chikungunya virus (CHIKV) was introduced into the Americas in 2013, its geographic distribution has rapidly expanded. Of 119 serum samples collected in 2014 from febrile patients in southern Mexico, 79% were positive for CHIKV or IgM against CHIKV. Sequencing results confirmed CHIKV strains closely related to Caribbean isolates.

Lead in candy consumed and blood lead levels of children living in Mexico City

BACKGROUND

Recent studies have shown that lead exposure continues to pose a health risk in Mexico. Children are a vulnerable population for lead effects and Mexican candy has been found to be a source of exposure in children. There are no previous studies that estimates lead concentrations in candy that children living in Mexico City consume and its association with their blood lead level.

OBJECTIVES

To evaluate whether there is an association between reported recent consumption of candies identified to have lead, and blood lead levels among children in Mexico City.

METHODS

A subsample of 171 children ages 2-6 years old, from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) cohort study was assessed between June 2006 and July 2007. The candy reported most frequently were analyzed for lead using ICP-MS. The total weekly intake of lead through the consumption of candy in the previous week was calculated. Capillary blood lead levels (BLL) were measured using LeadCare (anodic stripping voltammetry).

RESULTS

Lead concentrations ≥0.1ppm, the FDA permitted level (range: 0.13-0.7ppm) were found in 6 samples out of 138 samples from 44 different brands of candy. Median BLL in children was 4.5µg/dl. After adjusting for child's sex, age, BMI, maternal education & occupation, milk consumption, sucking the candy wrapper, use of lead-glazed pottery, child exposure behavior, living near a lead exposure site and use of folk remedies, an increase of 1µg of lead ingested through candy per week was associated with 3% change (95% CI: 0.1%, 5.2%) in BLL.

CONCLUSIONS

Although lead concentrations in candy were mostly below the FDA permitted level, high lead concentrations were detected in 4% of the candy samples and 12% of brands analyzed. Although candy intake was modestly associated with children's BLL, lead should not be found in consumer products, especially in candy that children can consume due to the well documented long-lasting effect of lead exposure.

Urinary 3-phenoxybenzoic acid (3-PBA) levels among pregnant women in Mexico City: Distribution and relationships with child neurodevelopment

BACKGROUND

In recent years, pyrethroid pesticide use has increased in Mexico, the United States, and elsewhere, resulting in extensive human exposure. There is growing concern that pregnant women may be a particularly vulnerable population, as in utero fetal exposure during critical periods of development could adversely affect long-term neurobehavioral function.

METHODS

We measured maternal urinary 3-phenoxybenzoic acid (3-PBA) concentrations during the third trimester of pregnancy as a measure of in utero pyrethroid exposure to the fetus among participants in an established Mexico City birth cohort (n=187). In a subset of mothers, we measured 3-PBA during the first, second, and third trimester (n=21) to assess variability across pregnancy. We examined associations between third trimester 3-PBA concentrations and children's scores on the Mental Development Index (MDI) and Psychomotor Development Index (PDI) from the Bayley Scales for Infant Development (BSID-IIS) at 24 and 36 months of age.

RESULTS

3-PBA was detected in 46% of all urine samples, with similar detection rates and geometric mean concentrations across pregnancy among the 21 participants who provided repeat samples. Participants in the medium and high 3-PBA categories (≥LOD) had lower MDI scores at 24 months compared to those in the low 3-PBA category (<LOD) after adjustment for covariates (ptrend=0.07), with slightly stronger associations among female children. The 3-level categorical variable for third trimester in utero 3-PBA was not associated with MDI scores at 36 months, or with PDI scores at either time point.

CONCLUSION

Considering the widespread agricultural and residential use of pyrethroids worldwide and the implications of cognitive and behavioral deficits, our findings indicate that additional study of in utero pyrethroid exposure and neurodevelopment in a larger study population is needed.

Triage strategies in cervical cancer detection in Mexico: methods of the FRIDA Study

OBJECTIVE

This paper describes the study design and baseline characteristics of the study population, including the first 30 829 women who enrolled in the Forwarding Research for Improved Detection and Access for Cervical Cancer Screening and Triage (FRIDA Study). This is a large population based study that is evaluating the performance and cost-effectiveness of different triage strategies for high-risk HPV (hrHPV) positive women in Mexico.

MATERIALS AND METHODS

The target population is more than 100 000 women aged 30 to 64 years who attend the Cervical Cancer Screening Program in 100 health centers in the state of Tlaxcala, Mexico. Since August 2013, all women in the region have been invited to enroll in the study. The study participants are evaluated to determine hrHPV infection using the Cobas 4800 HPV test. The HPV-16/18 genotyping and cytology triage strategies are performed as reflex tests in all hrHPV-positive participants. Women with a positive HPV-16/18 test and/or abnormal cytology (atypical squamous cells of undetermined significance or worse, ASCUS+) are referred for colposcopy evaluation, where a minimum of four biopsies and an endocervical sample are systematically collected. Histologic confirmation is performed by a standardized panel of pathologists.

RESULTS

Among the 30 829 women who have been screened, the overall prevalence of hrHPV is 11.0%. The overall prevalence of HPV16 and HPV18 are 1.5% and 0.7%, respectively. Cytological abnormalities (ASCUS+) were detected in 11.8% of the hrHPV-positive women. A total of 27.0% (920/3,401) of the hrHPV-positive women were referred to colposcopy because of a positive HPV16/18 test and/or abnormal reflex cytology, (31.6% had only ASCUS+, 53.6% were HPV16/18 positive with a normal cytology result, and 9.5% were positive to both triage tests).

CONCLUSION

The results of this study will help policy makers and health service providers establish the best practices for triage in cervical cancer screening in Mexico and other countries.

CD4 Counts at Entry to HIV Care in Mexico for Patients under the "Universal Antiretroviral Treatment Program for the Uninsured Population," 2007-2014

In Mexico, public health services have provided universal access to antiretroviral therapy (ART) since 2004. For individuals receiving HIV care in public healthcare facilities, the data are limited regarding CD4 T-lymphocyte counts (CD4e) at the time of entry into care. Relevant population-based estimates of CD4e are needed to inform strategies to maximize the impact of Mexico's national ART program, and may be applicable to other countries implementing universal HIV treatment programs. For this study, we retrospectively analyzed the CD4e of persons living with HIV and receiving care at state public health facilities from 2007 to 2014, comparing CD4e by demographic characteristics and the marginalization index of the state where treatment was provided, and assessing trends in CD4e over time. Our sample included 66,947 individuals who entered into HIV care between 2007 and 2014, of whom 79% were male. During the study period, the male-to-female ratio increased from 3.0 to 4.3, reflecting the country's HIV epidemic; the median age at entry decreased from 34 years to 32 years. Overall, 48.6% of individuals entered care with a CD4≤200 cells/μl, ranging from 42.2% in states with a very low marginalization index to 52.8% in states with a high marginalization index, and from 38.9% among individuals aged 18-29 to 56.5% among those older than 50. The adjusted geometric mean (95% confidence interval) CD4e increased among males from 135 (131,142) cells/μl in 2007 to 148 (143,155) cells/μl in 2014 (p-value<0.0001); no change was observed among women, with a geometric mean of 178 (171,186) and 171 (165,183) in 2007 and 2014, respectively. There have been important gains in access to HIV care and treatment; however, late entry into care remains an important barrier in achieving optimal outcomes of ART in Mexico. The geographic, socioeconomic, and demographic differences observed reflect important inequities in timely access to HIV prevention, care, and treatment services, and highlight the need to develop contextual and culturally appropriate prevention and HIV testing strategies and linkage programs.

A Large Proportion of the Mexican Population Remained Susceptible to A(H1N1)pdm09 Infection One Year after the Emergence of 2009 Influenza Pandemic

Background

The 2009 H1N1 influenza pandemic initially affected Mexico from April 2009 to July 2010. By August 2010, a fourth of the population had received the monovalent vaccine against the pandemic virus (A(H1N1)pdm09). To assess the proportion of the Mexican population who remained potentially susceptible to infection throughout the summer of 2010, we estimated the population seroprevalence to A(H1N1)pdm09 in a serosurvey of blood donors.

Methods

We evaluated baseline cross-reactivity to the pandemic strain and set the threshold for seropositivity using pre-pandemic (2005–2008) stored serum samples and sera from confirmed A(H1N1)pdm09 infected individuals. Between June and September 2010, a convenience sample serosurvey of adult blood donors, children, and adolescents was conducted in six states of Mexico. Sera were tested by the microneutralization (MN) and hemagglutination inhibition (HI) assays, and regarded seropositive if antibody titers were equal or exceeded 1:40 for MN and 1:20 for HI. Age-standardized seroprevalence were calculated using the 2010 National Census population.

Results

Sera from 1,484 individuals were analyzed; 1,363 (92%) were blood donors, and 121 (8%) children or adolescents aged ≤19 years. Mean age (standard deviation) was 31.4 (11.5) years, and 276 (19%) were women. A total of 516 (35%) participants declared history of influenza vaccination after April 2009. The age-standardized seroprevalence to A(H1N1)pdm09 was 48% by the MN and 41% by the HI assays, respectively. The youngest quintile, aged 1 to 22 years, had the highest the seroprevalence; 61% (95% confidence interval [CI]: 56, 66%) for MN, and 56% (95% CI: 51, 62%) for HI.

Conclusions

Despite high transmission of A(H1N1)pdm09 observed immediately after its emergence and extensive vaccination, over a half of the Mexican population remained potentially susceptible to A(H1N1)pdm09 infection. Subsequent influenza seasons with high transmission of A(H1N1)pdm09, as 2011–2012 and 2013–2014, are compatible with these findings.

Prevalence and Correlates of E-Cigarette Perceptions and Trial Among Early Adolescents in Mexico

PURPOSE

Assess the prevalence and correlates of e-cigarette perceptions and trial among adolescents in Mexico, where e-cigarettes are banned.

METHODS

Cross-sectional data were collected in 2015 from a representative sample of middle-school students (n = 10,146). Prevalence of e-cigarette awareness, relative harm, and trial were estimated, adjusting for sampling weights and school-level clustering. Multilevel logistic regression models adjusted for school-level clustering to assess correlates of e-cigarette awareness and trial. Finally, students who had tried only e-cigarettes were compared with students who had tried: (1) conventional cigarettes only; (2) both e-cigarettes and conventional cigarettes (dual triers); and (3) neither cigarette type (never triers).

RESULTS

Fifty-one percent of students had heard about e-cigarettes, 19% believed e-cigarettes were less harmful than conventional cigarettes, and 10% had tried them. Independent correlates of e-cigarette awareness and trial included established risk factors for smoking, as well as technophilia (i.e., use of more media technologies) and greater Internet tobacco advertising exposure. Exclusive e-cigarette triers (4%) had significantly higher technophilia, bedroom Internet access, and Internet tobacco advertising exposure compared to conventional cigarette triers (19%) and never triers (71%) but not compared to dual triers (6%), although dual triers had significantly stronger conventional cigarette risk factors.

CONCLUSIONS

This study suggests that adolescent e-cigarette awareness and use is high in Mexico, in spite of its e-cigarette ban. A significant number of medium-risk youth have tried e-cigarettes only, suggesting that e-cigarettes could lead to more intensive substance use. Strategies to reduce e-cigarette use should consider reducing exposures to Internet marketing.

[Analysis of the evidence on the efficacy and safety of CYD-TDV dengue vaccine and its potential licensing and implementation through Mexico's Universal Vaccination Program]

Dengue is a major global public health problem affecting Latin America and Mexico Prevention and control measures, focusing on epidemiological surveillance and vector control, have been partially effective and costly, thus, the development of a vaccine against dengue has created great expectations among health authorities and scientific communities worldwide. The CYD-TDV dengue vaccine produced by Sanofi-Pasteur is the only dengue vaccine evaluated in phase 3 controlled clinical trials. Notwithstanding the significant contribution to the development of a vaccine against dengue, the three phase 3 clinical studies of CYD-TDV and the meta-analysis of the long-term follow up of those studies, have provided evidence that this vaccine exhibited partial vaccine efficacy to protect against virologically confirmed dengue and lead to four considerations: a) adequate vaccine efficacy against dengue virus (DENV) infections 3 and 4, less vaccine efficacy against DENV 1 and no protection against infection by DENV 2; b) decreased vaccine efficacy in dengue seronegative individuals at the beginning of the vaccination; c) 83% and 90% protection against hospitalizations and severe forms of dengue, respectively, at 25 months follow-up; and d) increased hospitalization for dengue in the vaccinated group, in children under nine years of age at the time of vaccination, detected since the third year of follow-up. The benefit of the CYD-TDV vaccine can be summarized in the protection against infection by DENV 3 and 4, as well as protection for hospitalizations and severe cases in people over nine years, who have had previous dengue infection, working mainly as a booster. In this review we identified elements on efficacy and safety of this vaccine that must be taken into account in the licensing process and potential inclusion in the national vaccination program of Mexico. The available scientific evidence on the CYD-TDV vaccine shows merits, but also leads to relevant questions that should be answered to properly assess the safety profile of the product and the target populations of potential benefit. In this regard we consider it would be informative to complete the 6-year follow-up after starting vaccination, according to the company's own study protocol recommended by the World Health Organization. As with any new vaccine, the potential licensing and implementation of the CYD-TDV as part of Mexico's vaccination program, requires a clear definition of the balance between the expected benefits and risks. Particularly with a vaccine with variable efficacy and some signs of risk, in the probable case of licensing, the post-licensed period must involve the development of detailed protocols to immediately identify risks or any health event associated with vaccination.

[Decrease of HCV seroprevalence in Mexico: Results from the National Health and Nutrition Survey 2012]

OBJECTIVE

To estimate seroprevalence of hepatitis C virus (HCV) among 15-49 years old Mexicans living in households and to describe the profile of seroreactive individuals.

MATERIALS AND METHODS

Cross-sectional study implemented in 2012 using a national probabilistic sample with behavioral data from face-to-face interviews at households and HCV antibodies screening using capillary blood from same individuals.

RESULTS

HCV seroprevalence in Mexico was estimated at 0.27% (IC95% 0.12-0.60), representing 161 000 persons. Seroprevalence was significantly higher among males (0.45% CI95% 0.01-0.89) than females (0.10% CI95% 0.00-0.22). Multivariate analysis suggests a higher possibility of HCV reactivity among men, increasing with age and higher among those sexually active, and lower for higher socioeconomic level.

CONCLUSION

HCV seroprevalence in Mexico by 2012 seems significantly lower than the estimation from 2000 of 1.2% for the same age-group. Evidence of infection among individuals 15-19 years old suggests the need to strength preventive actions, particularly in subjects with risky behaviors.

Differential association of lead on length by zinc status in two-year old Mexican children

BACKGROUND

Blood lead levels have decreased in Mexico since leaded fuel was banned in 1997, but other sources remain, including the use of lead-glazed ceramics for food storage and preparation. Zinc deficiency is present in almost 30% of children aged 1-2 years. Previous studies have documented negative associations of both lead exposure and zinc deficiency with stature, but have not considered the joint effects. Given that the prevalence of stunting in pre-school aged children was 13.6% in 2012, the aim of this study was to evaluate if the relationship between blood lead and child stature was modified by zinc status.

METHODS

Anthropometry, dietary energy intake, serum zinc and blood lead were measured in 291 children aged 24 months from an ongoing birth cohort study in Mexico City. Child stature was represented by recumbent length as appropriate for this age group. The association between blood lead (BPb) and length-for-age Z score (LAZ) was evaluated using a model stratified by zinc status measured by standard criteria and adjusted for: birth length, breastfeeding practices, energy intake, maternal height and education.

RESULTS

Median (IQR) BPb was: 0.17 (0.12-0.26) μmol/L and 17% of the sample had zinc deficiency (<9.9 μmol/L). BPb was inversely associated with LAZ in the overall sample (β = -0.19, p = 0.02). In stratified models, this negative association was more than three times higher and statistically significant only in the zinc deficient group (β = -0.43, p = 0.04) compared to the zinc replete group (β = -0.12, p = 0.22) (BPb*zinc status, p-for-interaction = 0.04).

CONCLUSIONS

Zinc adequacy is a key factor that may attenuate the negative association of lead on stature in young children.

Burden of type 2 diabetes in Mexico: past, current and future prevalence and incidence rates

INTRODUCTION

Mexico diabetes prevalence has increased dramatically in recent years. However, no national incidence estimates exist, hampering the assessment of diabetes trends and precluding the development of burden of disease analyses to inform public health policy decision-making. Here we provide evidence regarding current magnitude of diabetes in Mexico and its future trends.

METHODS

We used data from the Mexico National Health and Nutrition Survey, and age-period-cohort models to estimate prevalence and incidence of self-reported diagnosed diabetes by age, sex, calendar-year (1960-2012), and birth-cohort (1920-1980). We project future rates under three alternative incidence scenarios using demographic projections of the Mexican population from 2010-2050 and a Multi-cohort Diabetes Markov Model.

RESULTS

Adult (ages 20+) diagnosed diabetes prevalence in Mexico increased from 7% to 8.9% from 2006 to 2012. Diabetes prevalence increases with age, peaking around ages 65-68 to then decrease. Age-specific incidence follows similar patterns, but peaks around ages 57-59. We estimate that diagnosed diabetes incidence increased exponentially during 1960-2012, roughly doubling every 10 years. Projected rates under three age-specific incidence scenarios suggest diabetes prevalence among adults (ages 20+) may reach 13.7-22.5% by 2050, affecting 15-25 million individuals, with a lifetime risk of 1 in 3 to 1 in 2.

CONCLUSIONS

Diabetes prevalence in Mexico will continue to increase even if current incidence rates remain unchanged. Continued implementation of policies to reduce obesity rates, increase physical activity, and improve population diet, in tandem with diabetes surveillance and other risk control measures is paramount to substantially reduce the burden of diabetes in Mexico.

Price elasticity of the demand for sugar sweetened beverages and soft drinks in Mexico

A large and growing body of scientific evidence demonstrates that sugar drinks are harmful to health. Intake of sugar-sweetened beverages (SSB) is a risk factor for obesity and type 2 diabetes. Mexico has one of the largest per capita consumption of soft drinks worldwide and high rates of obesity and diabetes. Fiscal approaches such as taxation have been recommended as a public health policy to reduce SSB consumption. We estimated an almost ideal demand system with linear approximation for beverages and high-energy food by simultaneous equations and derived the own and cross price elasticities for soft drinks and for all SSB (soft drinks, fruit juices, fruit drinks, flavored water and energy drinks). Models were stratified by income quintile and marginality index at the municipality level. Price elasticity for soft drinks was -1.06 and -1.16 for SSB, i.e., a 10% price increase was associated with a decrease in quantity consumed of soft drinks by 10.6% and 11.6% for SSB. A price increase in soft drinks is associated with larger quantity consumed of water, milk, snacks and sugar and a decrease in the consumption of other SSB, candies and traditional snacks. The same was found for SSB except that an increase in price of SSB was associated with a decrease in snacks. Higher elasticities were found among households living in rural areas (for soft drinks), in more marginalized areas and with lower income. Implementation of a tax to soft drinks or to SSB could decrease consumption particularly among the poor. Substitutions and complementarities with other food and beverages should be evaluated to assess the potential impact on total calories consumed.

Evaluating the validity of self-reported smoking in Mexican adolescents

OBJECTIVES

We aimed to evaluate the validity of the self-reported smoking indicator used in the Global Youth Tobacco Survey (GYTS).

SETTING

43 middle and high-school classrooms from 26 schools were selected from Mexico City and Cuernavaca, Morelos.

PARTICIPANTS

A total of 1257 students provided both a questionnaire and a urine sample.

PRIMARY AND SECONDARY OUTCOME

Sensitivity and specificity of self-reported smoking compared to urinary cotinine. Validity indices were evaluated by subgroups of gender, social acceptability of smoking (ie, smoking parents or friends) and smoking frequency.

RESULTS

Sensitivity and specificity for current smoking were 93.2% and 81.7%, respectively. Validity indices remained stable across gender. Parental smoking status moderated the validity of self-report, which had lower sensitivity in adolescents with non-smoking parents (86.7%) than in adolescents with smoking parents (96.6%). Sensitivity and specificity increased with smoking frequency.

CONCLUSIONS

This first validation study of self-reported current smoking used in the GYTS among Mexican adolescents suggests that self-reported smoking in the past 30 days is a valid and stable indicator of current smoking behaviour. This measure appears suitable for public health research and surveillance.

Prediction of Serum Zinc Levels in Mexican Children at 2 Years of Age Using a Food Frequency Questionnaire and Different Zinc Bioavailability Criteria

BACKGROUND

The 2006 Mexican National Health and Nutrition Survey documented a prevalence of zinc deficiency of almost 30% in children under 2 years of age.

OBJECTIVE

We sought to validate a food frequency questionnaire (FFQ) for quantifying dietary bioavailable zinc intake in 2-year-old Mexican children accounting for phytic acid intake and using serum zinc as a reference.

METHODS

This cross-sectional study was nested within a longitudinal birth cohort of 333 young children in Mexico City. Nonfasting serum zinc concentration was measured and dietary zinc intake was calculated on the basis of a semiquantitative FFQ administered to their mothers. The relationship between dietary zinc intake and serum zinc was assessed using linear regression, adjusting for phytic acid intake, and analyzed according to two distinct international criteria to estimate bioavailable zinc. Models were stratified by zinc deficiency status.

RESULTS

Dietary zinc, adjusted for phytic acid intake, explained the greatest proportion of the variance of serum zinc. For each milligram of dietary zinc intake, serum zinc increased on average by 0.95 μg/dL (0.15 μmol/L) (p = .06). When stratified by zinc status, this increase was 0.74 μg/dL (p = .12) for each milligram of zinc consumed among children with adequate serum zinc (n = 276), whereas among those children with zinc deficiency (n = 57), serum zinc increased by only 0.11 μg/dL (p = .82).

CONCLUSIONS

A semiquantitative FFQ can be used for predicting serum zinc in relation to dietary intake in young children, particularly among those who are zinc-replete, and when phytic acid or phytate intake is considered. Future studies should be conducted accounting for both zinc status and dietary zinc inhibitors to further elucidate and validate these findings.