Environment driven changes in type 2 diabetes, overweight and obesity in an isolated Mixe community in the Valley of Oaxaca, southern Mexico.

BACKGROUND: This study focused on type 2 diabetes mellitus (T2DM) in a group of adult Mixe, an Indigenous population from Oaxaca, Mexico. Mixe comprised an estimated 9.4% (n ≅ 90 000) of the Indigenous population in Oaxaca. Mexico. OBJECTIVE: This study focused on a group of adult Mixe, an Indigenous population from Oaxaca, Mexico. To compare the prevalence of T2DM, overweight (OW), obesity (OB), and hypertension (HTN) between 2007 and 2017 for a small, isolated Mixe community in the Valley of Oaxaca, Mexico. We test whether or not environmental changes have affected T2DM prevalence. METHODS AND MATERIALS: Demographic and medical record data were collected in the community in 2007 and 2017 from the medical clinic and the mayor's office. T2DM was medically diagnosed among adults (>34 years old), in 2007 (n = 730) and in 2017 (n = 829). RESULTS: T2DM crude prevalence increased from 6.7% to 12.1% (p < .001) from 2007 to 2017. The mean age of the sample analyzed was 60.6 (SD = 9.7). Age-adjusted T2DM prevalence increased from 6.7% to 10.8% (p < .002). T2DM was 5.7%-5.5% among males (p < .53) and 7.1%-13.6% among females (p < .001). Sex-specific OW and OB simulation studies indicate females had 7% less OW in 2007, and males were unchanged compared with 2017. OB among males and females was significantly higher in 2017 compared with 2007 (increased by 15.2% and 8.3%, males and females, respectively). Sexes combined OW + OB increased 12.7% among males but was unchanged in females (-0.5%). In the sexes combined analysis, OW prevalence increased 12.7% to 27.1% (p < .001) and OB prevalence increased 10.7%-27.9% (p < .001) from 2007 to 2017. HTN did not change significantly from 2007 to 2017 (15.4% and 14.6%, respectively) (p = .63) in adults. Among T2DM individuals, the frequency of HTN was not significantly different in 2007 and 2017 (57.1% and 37%, respectively) (p = .65). Transition to a Western diet consisting of high-carbohydrate foods occurred at the same time as increased T2DM from 2007 to 2017, with a higher prevalence of T2DM noted among females in 2017. CONCLUSIONS: An increased prevalence of T2DM, OW, and OB but not HTN was observed in the Mixe community from 2007 to 2017 and was associated with the adoption of a high-carbohydrate Western diet.

Thinness, overweight, and obesity in indigenous school children and youth in Mexico.

Background: The prevalence of overweight (OWT) and obesity (OB), defined by the body mass index (BMI, kg/m2) among children and youth has increased worldwide in the last 30-40 years.Aim: To evaluate the weight status, defined by the BMI, of indigenous school children and youth resident in different regions of MexicoSubjects and methods: Students 6-18 years (31,448 boys, 27,306 girls) were enrolled in bilingual schools for indigenous children and youth in Mexico in 2012. Height and weight were measured; the BMI was calculated. The BMI of each student was classified relative to International Obesity Task Force (IOTF) age- and sex-specific criteria as thin (three grades), normal, overweight (OWT) or obese (OB). The sample was divided into five geographic regions for analysis: North, Central, South-Gulf, South-Pacific, and South-Southeast. Age- and sex-specific prevalence, 95% confidence intervals, and Chi-square tests were calculated.Results: Prevalence of OWT + OB was highest in the South-Gulf, South-Pacific and South-Southeast regions and lowest in the North and Central regions, while thinness was most prevalent in the North and Central regions.Conclusion: Prevalence of severe and moderate thinness was relatively low, while the combined prevalence of OWT + OB was generally more prevalent in indigenous boys than girls. However, the prevalence of thinness, OWT + OB among indigenous children and youth was lower than in the general population of children and youth in Mexico.

Secular trends are associated with the demographic and epidemiologic transitions in an indigenous community in Oaxaca, Southern Mexico.

OBJECTIVE: To test the hypothesis that secular changes in body size and age at menarche are related to the demographic and epidemiologic transitions in an indigenous community in Oaxaca, southern Mexico. METHODS: Data were derived from surveys of a Zapotec-speaking community conducted between 1968 and 2000. Segmented linear regressions of height, weight, BMI and recalled age at menarche on year of birth in cohorts of adults born before and after the demographic transition were used to evaluate secular changes. Corresponding comparisons of body size (MANCOVA controlling for age) and age at menarche (status quo, probit analysis) were done for samples of children and adolescents born before and after the epidemiological transition. RESULTS: Height and weight increased in adults born after the demographic transition (mid-1950s), and especially in children and adolescents born after the epidemiological transition (mid-1980s). Age at menarche also decreased significantly in women born after the demographic transition, but at a more rapid estimated rate in adolescents born after the epidemiological transition. Secular gains in body weight were proportional to those for height among children and adolescents, but adults, males more so than females, gained proportionally more weight. CONCLUSIONS: The secular trend in height in adults of both sexes was associated with the decade of the demographic transition in the mid-1950s. Significant secular gains in size attained and age at menarche occurred in children and youth born after the epidemiologic transition which likely reflected improved health and nutritional conditions since the mid-1980s.

Geographic variation in the growth status of indigenous school children and youth in Mexico.

OBJECTIVE: To analyze variation in the growth status of indigenous children and youth attending bilingual schools, escuelas albergues, for the indigenous population in México. MATERIALS AND METHODS: The children and youth attended escuelas albergues in 1,009 localities in 21 Mexican states in 2012. Heights and weights of 31,448 boys and 27,306 girls 6-18 years of age were measured by trained staff at each school; the BMI was calculated. The students were divided into five geographic regions for analysis: North, Central, South-Gulf, South-Pacific, and South-Southeast. Growth status was compared to United States reference percentiles (P). RESULTS: Mean heights of children and youth from the five regions varied between P10 and P5 of the reference until about 13 years (girls) and 14 years (boys); subsequently, heights were ≤P5. Mean weights in both sexes were at P25 of the reference between 6 and 12 years, and then varied between P25 and P10 in boys and were ≥P25 in girls. Given the elevated weights relative to heights compared to the reference, mean BMIs of indigenous boys and girls were at or above the reference medians. Children and youth in the North and Central regions were, on average, taller than those in the South-Pacific and South-Southeast regions, while heights of those in the South-Gulf region were generally intermediate. In contrast, mean weights and BMIs differed negligibly among the regions. CONCLUSIONS: The geographic gradient in heights of indigenous children and youth was consistent with a north-to-south pattern noted among indigenous adults in studies spanning 1898 through 2013. Variation in height among children and youth likely reflected ethnic-specific and geographic variation interacting with economic and nutritional factors.

Natural selection and type 2 diabetes-associated mortality in an isolated indigenous community in the valley of Oaxaca, southern Mexico.

OBJECTIVE: This study tests the hypothesis that natural selection is associated with type 2 diabetes (T2D)-associated mortality and fertility in a rural isolated Zapotec community in the Valley of Oaxaca, southern Mexico. PARTICIPANTS AND METHODS: Mortality data and related demographic and genealogic information were linked with data for fertility, prereproductive mortality and family history of mortality attributed to T2D. Physician verified T2D mortality (n = 27) between 1980 and 2009 and imputed T2D (n = 70) from cardiovascular mortality (68% random sample) and renal failure (44% random sample). Bootstrapping was used to obtain a robust variance estimate in survival analysis and multivariate analysis of variance. RESULTS: Estimated maximum natural selection by Crow's Index occurred circa 1930 and was relaxed after this time in the study population. Cox-regression survival analysis of T2D mortality with covariates (family history of T2D, cardiovascular disease, renal failure) indicated a significant hazard ratio (HR = 5.95, 95% CI: 1.38-25.67, p < .008) for the increase in T2D in 2000 to 2009. Survival analysis of imputed T2D resulted in a significant HR of 2.03 (95% CI: 1.08-3.85, p = .01) for the increase in T2D in the 2000 to 2009 cohort (reference group: 1980-1989). Mean number of live born offspring was lower among T2D (n = 27, 4.04 ± 3.85 SD) compared to non-T2D (n = 199, 5.30 ± 3.48) groups (p < .08). Mean number of live born offspring was lower (p = .003) among imputed T2D compared to non-T2D groups (4.10 ± 3.44 vs. 5.62 + 3.50). DISCUSSION: T2D-associated mortality increased in frequency as natural selection decreased, and favored offspring survival of non-T2D descedants. The results indicated statistically significant directional selection against T2D and imputed T2D to this population isolate.

Tracking anthropometric dimensions and grip strength among children, adolescents and adults in an indigenous community of southern Mexico: 1968-1978-2000.

PURPOSE: To track body size and proportions, arm dimensions and grip strength in children, adolescents, and adults resident in an indigenous community in Oaxaca who were measured on two or three occasions across surveys in 1968, 1978, and 2000. METHODS: The three cross-sectional surveys included measures of height, weight, sitting height, arm circumference, triceps skinfold, and grip strength in surveys of schoolchildren in 1968 and of schoolchildren, adolescents and adults in 1978 and 2000. Cross-checks of surnames, forenames and ages/dates of birth of participants in the three surveys identified three samples of individuals measured on two occasions (1968-1978, two age groups in 1978-2000) and a subsample of individuals measured in the three surveys. Partial correlations controlling for age at each observation were calculated for each variable in the three sex-specific samples measured on two occasions, and for the subsamples of males and females measured on three occasions. RESULTS: Allowing for variation in age among subsamples, inter-age correlations were moderate to high for stature, moderate for sitting height and estimated leg length, and low to moderate for weight, BMI, arm and estimated arm muscle circumference, triceps skinfold, and grip strength. CONCLUSION: Allowing for the relatively broad chronological age intervals, the inter-age correlations for height, weight and BMI were at the low end, while those for grip strength and for strength per unit body weight for males (though not females) were generally in the range of correlations noted in studies of European samples. Likely associated with improved health, nutritional, and sanitation conditions, obesity and overweight were emerging among adults by 2000. Obesity and overweight in adults paralleled the introduction of mechanized agriculture that reduced routine physical work. Among children, the association of obesity and overweight is likely with increased nutritional availability, but poor choices in diet.

Altitude effects on growth of indigenous children in Oaxaca, Southern Mexico.

The effect of altitude of residence on the growth status of 11,454 indigenous school children 6-14 years of age in Oaxaca, southern Mexico, was examined. Indicators of living conditions (human development index [HDI], index of community nutritional risk [INR], index of marginalization [IM], index of relative isolation [II]) were regressed on z-scores for height, weight and BMI, and the residuals were regressed on altitude of residence (km). Independent of other environmental conditions, altitude negatively affected height by approximately -0.07 z-scores per kilometer altitude above sea level. The estimated average decrease in stature was 0.92 cm per kilometer elevation. BMI was significantly increased, 1.2 units per kilometer elevation, consistent with earlier studies of growth status and altitude. In contrast, weight was not affected by altitude of residence. Approximately 36% of the reduction in height and 54% of the increase in BMI were due to altitude effects; the remaining changes in height and BMI were associated with environmental factors reflected in the indices of community well-being considered.

Thinness, overweight and obesity in indigenous youth in Oaxaca, 1970 and 2007.

OBJECTIVE: To evaluate change in body mass index (BMI) and weight status of indigenous youth in Oaxaca between the 1970s and 2007. MATERIALS AND METHODS: Heights and weights were measured in cross-sectional samples of school children 6-14 years in the 1970s (2 897) and 2007 (4 305); BMI was calculated. International Obesity Task Force cutoffs for weight status were used. BMI and prevalence of severe and moderate thinness, overweight and obesity were compared by year. RESULTS: BMI increased significantly across time. Primary change in weight status occurred in overweight, 1970s, <2%; 2007, 7 to 12%. Little change occurred in thinness (<2%) and obesity (≤ 1%) in both surveys, except in children 6-9 years (obesity=4% in 2007). CONCLUSION: BMI and prevalence of overweight increased across all ages from the 1970s to 2007, but children 6-9 years appeared to be more at risk for obesity than youth 10-14 years. Prevalence of thinness was unchanged.

Secular change in height and weight of indigenous school children in Oaxaca, Mexico, between the 1970s and 2007.

BACKGROUND: Information on secular change in indigenous children in Oaxaca, southern Mexico, is limited. AIM: To evaluate secular change in heights and weights of indigenous school children 6-14 years in four regions of the state of Oaxaca between the 1970s and 2007. SUBJECTS AND METHODS: Heights and weights of 2897 (1419 boys, 1478 girls) and 4305 (2368 boys, 1937 girls) school children 6-14 years of age were measured in the 1970s (1971-1978) and 2007, respectively. The sample was from 18 communities in the 1970s and from 58 communities in 2007 in four regions of Oaxaca. Sex-specific MANCOVA, with age of the child and altitude of each community as covariates, was used to compare size attained in the 1970s and 2007 in two age groups: 6-9 years and 10-14 years. RESULTS: Indigenous Oaxaca school children are taller and heavier in 2007 than the 1970s. Secular gains are larger in youth of 10-14 years than in children of 6-9 years, while sex differences are small. CONCLUSION: Improved growth status between the 1970s and 2007 presumably reflects better health and nutritional conditions in indigenous communities of Oaxaca. Mean heights in 2007, however, only approximate 5(th) percentiles of the US reference.

Skeletal age in youth soccer players: implication for age verification.

OBJECTIVE: To evaluate variation in skeletal age (SA) within single-year chronological age (CA) groups of soccer players aged 11 to 17 years in the context of using SA for age verification in age-group competitions. DESIGN: Cross sectional. SETTING: Regional and elite youth soccer programs. PARTICIPANTS: Five hundred ninety-two male players from Portugal and Spain. INDEPENDENT VARIABLES: Skeletal age assessed with the Fels method. MAIN OUTCOME MEASURES: Skeletal age and maturity status (late, average, early, or mature). RESULTS: Chronological age and SA overlapped in players aged 11 to 12 years, but SA was advanced relative to CA in players aged 14 to 16 years. The majority of players between 11 and 12 years of age were on time in skeletal maturity and percentages of late and early maturers did not differ. The majority of players between 13 and 14 years of age were also on time, but early maturers were 4 times more frequent than late maturers. Percentages of late maturers were low among players aged 14 to 16 years. Among 200 players aged 15 to 16 years, 80 (40%) were advanced in SA by > 1 year and 27 (14%) were skeletally mature, whereas among 23 players aged 17 years, 9 (39%) were skeletally mature. CONCLUSIONS: Among adolescent soccer player, boys advanced in SA for CA are overrepresented and those later in SA for CA are underrepresented with increasing CA. If Fels SA was used to verify CA in this sample of youth for under-17 competition, 36 skeletally mature players aged 15 to 17 years (16%) would be disqualified. The results for this sample of male soccer players question the utility of SA or magnetic resonance imaging as a valid estimate of CA in youth sport competitions.

Do mating preferences remain the same when phenotypes change? Assortative mating for physical characteristics in an indigenous community in the valley of Oaxaca, southern Mexico.

Objective. To test the hypothesis that assortative mating for physical characteristics differs before and after major secular increases in height in an indigenous community in the Valley of Oaxaca, Mexico. Methods. Spouse pairs were identified in household and anthropometric surveys of a Zapotec-speaking community in 1978 (n = 68-70 pairs) and 2000 (n = 99-100 pairs). Height, weight, arm circumference, triceps skinfold and grip strength were measured. Assortative mating was calculated as Pearson correlations. Results. Husband-wife correlations for age were high in both years (r = 0.96, 0.95). Assortative mating for height was significant in 1978 (r = 0.35, p < 0.001) and in 2000 (r = 0.21, p < 0.01), but decreased when ages were controlled (1978, 0.21, p < 0.05; 2000, 0.11). Correlations (zero and second order, respectively) were low for the BMI (1978, 0.02, 0.02; 2000, 0.04, 0.05). Spouse correlations for grip strength were significant in both surveys (r = 0.25 to 0.45), but were reduced (p > 0.05) when ages of spouses were controlled (r = -0.02 to 0.16). Conclusion. Assortative mating for physical characteristics did not differ between surveys conducted before (1978) and after (2000) major secular increases in height in the community, and any possible genetic effect of the secular trend on assortative was likely negligible.

Growth status of indigenous school children 6-14 years in the Tarahumara Sierra, Northern Mexico, in 1990 and 2007.

AIMS: The study evaluated the growth status and secular change in body size of indigenous Tarahumara children in northern Mexico. METHODS: Heights and weights of Tarahumara children 6-14 years were measured in 1990 (n = 601) and 2007 (n = 583); the BMI was calculated. International criteria defined weight status while United States reference data defined stunting. RESULTS: Estimated secular gains in height from 1990 to 2007 were greatest in 6-7 year-old boys and declined with age to a small, non-significant secular decline in boys 12-14 years. Among girls secular gains in height were similar at 6-7 and 8-9 years, largest at 10-11 years and small and non-significant at 12-14 years. Secular gains in weight were similar among 6-7 and 8-9 year-old boys and girls, were greater in girls than in boys at 10-11 years and showed a small, non-significant secular decline in boys and girls 12-14 years. Secular change in the BMI paralleled those for weight. The prevalence of stunting declined from 1990 to 2007 in both sexes and all age groups except 12-14 year youth. Overweight was more prevalent in girls than boys in both years and increased from 4% to 7% in boys and 9% to 13% in girls. Obesity was not common among boys and girls in each age group and in both years. Stunting and overweight/obesity were not related in either 1990 or 2007. CONCLUSION: Positive secular changes in growth status have occurred in Tarahumara children 6-11 years in contrast to negligible changes among children 12-14 years. The results suggest recent improvements in health and nutrition sufficient to support a positive secular trend in younger children.

Epidemiologic transition in an isolated indigenous community in the Valley of Oaxaca, Mexico.

The objective of the present study is to analyze age-specific mortality in a rural indigenous community in the throes of a secular increase in size in the Valley of Oaxaca, southern Mexico, over 30 years, 1970-1999. Variation in mortality by age group was analyzed over time for evidence of an epidemiological transition. The seasonal rain pattern in the Valley of Oaxaca (83% from May through September) was evaluated for its relationship with mortality in wet and dry months. Mortality and causes of death changed markedly over the 30-year interval. Infant and preschool mortality, overall mortality, and causes of death changed from the 1970s through the 1990s. Prereproductive deaths (<15 years) predominated in the 1970s and were largely due to gastrointestinal and respiratory diseases, with periodic outbreaks of measles. Deaths of adults 65+ years predominated in the 1990s and were largely due to degenerative diseases usually associated with aging. The marked changes in age and causes of death over the three decades (epidemiologic transition from Stage I to Stage II) occurred concurrently with significant secular increases in body size in children, adolescents, and young adults, highlighting improved health and nutritional conditions in the community which is in early Stage II of the demographic transition. The demographic transition to Stage II is a leading indicator (15-25 years lag) for the onset of the secular trend, while the epidemiologic transition to Stage II is a predictor that the secular increase is in process in the study community.

Secular change in the growth status of urban and rural schoolchildren aged 6-13 years in Oaxaca, southern Mexico.

BACKGROUND: Populations in the state of Oaxaca in southern Mexico are at high risk for malnutrition and marginalization. AIM: The study compared secular changes in the growth status of urban and rural schoolchildren in the Valley of Oaxaca between the 1970s and 2000. SUBJECTS AND METHODS: Cross-sectional surveys of boys and girls aged 6-13 years (n = 1472) were carried out in an urban colonia populares in 1972 and 2000 and a rural indigenous community in 1978 and 2000. Height, sitting height and weight were measured; leg length, sitting height ratio, BMI, and prevalence of stunting, underweight, overweight and obesity were calculated. Sex-specific ANCOVA controlling for age was used. RESULTS: Both urban and rural children experienced significant secular gains in linear dimensions, body weight and the BMI between the 1970s and 2000. Estimated rates of secular gain overlapped considerably between urban and rural children. Secular gains in the BMI are significantly greater in urban than rural boys and girls. Urban-rural differences in linear dimensions and body weight in 2000 compared to the 1970s do not differ in either sex, but urban-rural differences in the BMI are greater in boys and girls in 2000 compared to the 1970s. The prevalence of stunting declined while that of overweight and obesity increased. CONCLUSIONS: Significant secular increases in body size occurred between the 1970s and 2000, but there was considerable overlap between urban and rural children. Only secular gains in the BMI were significantly greater in urban than rural boys and girls and the magnitudes of urban-rural differences in the BMI were greater in 2000 than in the 1970s.

Tanner-Whitehouse Skeletal Ages in Male Youth Soccer Players: TW2 or TW3?

BACKGROUND: The Tanner-Whitehouse radius-ulna-short bone protocol (TW2 RUS) for the assessment of skeletal age (SA) is widely used to estimate the biological (skeletal) maturity status of children and adolescents. The scale for converting TW RUS ratings to an SA has been revised (TW3 RUS) and has implications for studies of youth athletes in age-group sports. OBJECTIVES: The aim of this study was to compare TW2 and TW3 RUS SAs in an international sample of male youth soccer players and to compare distributions of players by maturity status defined by each SA protocol. METHODS: SA assessments with the TW RUS method were collated for 1831 male soccer players aged 11-17 years from eight countries. RUS scores were converted to TW2 and TW3 SAs using the appropriate tables. SAs were related to chronological age (CA) in individual athletes and compared by CA groups. The difference of SA minus CA with TW2 SA and with TW3 SA was used to classify players as late, average, or early maturing with each method. Concordance of maturity classifications was evaluated with Cohen's Kappa coefficients. RESULTS: For the same RUS score, TW3 SAs were systematically and substantially reduced compared with TW2 SAs; mean differences by CA group ranged from - 0.97 to - 1.16 years. Kappa coefficients indicated at best fair concordance of TW2 and TW3 maturity classifications. Across the age range, 42% of players classified as average with TW2 SA were classified as late with TW3 SA, and 64% of players classified as early with TW2 SA were classified as average with TW3 SA. CONCLUSION: TW3 SAs were systematically lower than corresponding TW2 SAs in male youth soccer players. The differences between scales have major implications for the classification of players by maturity status, which is central to some talent development programs.

Thinness, overweight and obesity in indigenous youth in Oaxaca, 1970 and 2007 / Delgadez, sobrepeso y obesidad en jóvenes indígenas en Oaxaca, 1970 y 2007

Objective. To evaluate change in body mass index (BMI) and weight status of indigenous youth in Oaxaca between the 1970s and 2007. Materials and methods. Heights and weights were measured in cross-sectional samples of school children 6-14 years in the 1970s (2 897) and 2007 (4 305); BMI was calculated. International Obesity Task Force cutoffs for weight status were used. BMI and prevalence of severe and moderate thinness, overweight and obesity were compared by year. Results. BMI increased significantly across time. Primary change in weight status occurred in overweight, 1970s, <2%; 2007, 7 to 12%. Little change occurred in thinness (<2%) and obesity (≤1%) in both surveys, except in children 6-9 years (obesity=4% in 2007). Conclusion. BMI and prevalence of overweight increased across all ages from the 1970s to 2007, but children 6-9 years appeared to be more at risk for obesity than youth 10-14 years. Prevalence of thinness was unchanged.

Objetivo. Evaluar el cambio en el índice de masa corporal (IMC) y el estatus de peso entre 1970 y 2007 en jóvenes indígenas de Oaxaca. Material y métodos. Se midieron estatura y peso de series transversales de escolares indígenas en edades de 6 a 14 años en 1970 (2 897) y en 2007 (4 305), se calculó el IMC y se emplearon los puntos de corte del International Obesity Task Force para el estatus de peso. El IMC y la prevalencia de delgadez, sobrepeso y obesidad en 1970 y 2007 fueron comparados. Resultados. El IMC aumentó de manera significativa entre 1970 y 2007. Los cambios más importantes fueron en sobrepeso, <2% en 1970 a 7-12% en 2007. Hubo poco cambio en la delgadez (<2%) y la obesidad (≤1%) en ambas investigaciones, excepto en niños de 6 a 9 años (4% en 2007). Conclusión. El IMC y la prevalencia de sobrepeso aumentaron a través de todas las edades de los años 1970 a 2007, pero los niños de 6 a 9 años parecen tener un mayor riesgo para la obesidad que los jóvenes de 10 a 14 años. La frecuencia de la delgadez fue igual.

Craniofacial dimensions in children in rural Oaxaca, southern Mexico: secular change, 1968-2000.

The objective of this investigation was to analyze the underlying cause(s) of secular changes in craniofacial dimensions among indigenous children in an isolated community in Oaxaca, southern Mexico, between 1968-2000. Subjects were schoolchildren resident in a rural, agrarian, Zapotec-speaking community in the Valley of Oaxaca, previously characterized as mildly-to-moderately undernourished with growth-stunting in 1968 and 1978. In 2000, children had experienced a secular increase in height compared with two prior growth surveys. Four craniofacial dimensions (head length, head breadth, and bizygomatic and bigonial breadths) were measured during anthropometric surveys of schoolchildren aged 6-13 years in 1968, 1978, and 2000. Cephalic and zygomandibular indices were calculated. Samples by survey were: 1968, 151 males and 157 females; 1978, 179 males and 184 females; and 2000, 180 males and 186 females. The analysis was based on a total of 1,037 children. Multivariate analysis of covariance was used to assess secular trend effects, with height, age, and age2 as covariates by sex. Over the interval of 32 years, significant secular changes occurred in craniofacial dimensions and one index: 1) head length was shorter in boys and girls; 2) bizygomatic breadth was narrower in boys and girls; 3) head breadth increased over time only among girls; 4) brachycephalization increased significantly in a linear manner among both sexes; and 5) the zygomandibular index decreased significantly only in boys. Thus, the cranial complex remodeled to a shorter head length, both relatively (brachycephalization) and absolutely. Remodeling over time also resulted in a narrower face, with the midface changing at about the same rate as the lower face (i.e., mandible). Secular changes are generally recognized as multifactorial. Changes in the cephalic index and cranium over time in schoolchildren in an isolated rural agrarian Zapotec-speaking community in the Valley of Oaxaca suggest that the underlying forces for the secular change are associated: 1) decreased food (maize) coarseness or grit content (masticatory stress), and 2) relaxed natural selection, resulting in 3) a greater role for developmental plasticity.

Urban-rural contrasts in the physical fitness of school children in Oaxaca, Mexico.

The physical fitness of school children resident in an urban colonia and in a rural indigenous community in Oaxaca, southern Mexico, was compared. Two measures of performance-related fitness (standing long jump, 35-yard dash [32 m]) and four measures of health-related fitness (grip strength, sit and reach, timed sit-ups, distance run) were taken on 355 rural (175 boys, 184 girls) and 324 urban (163 boys, 161 girls) school children, 6-13 years of age. Urban children were significantly taller and heavier than rural children. Absolute grip strength did not consistently differ between rural and urban children, but when adjusted for age and body size, strength was greater in rural children. Explosive power (standing long jump) and abdominal strength and endurance (timed sit-ups) were better in urban than in rural children without and with adjustment for age and body size. Urban-rural differences in running speed (dash) and flexibility (sit and reach) varied by age group and sex. Younger rural children and older urban girls performed better in the distance run, whereas older rural and urban boys did not differ in endurance. The size advantage of urban children does not necessarily translate into better levels of performance- and health-related physical fitness. The observed differences may be related to activity habits associated with school physical education and lifestyle in the respective communities.