Noel Cameron - Academia.edu (original) (raw)

Papers by Noel Cameron

American Journal of Human Biology, 2000

This study presents cross-sectional data from an ongoing mixed-longitudinal study of growth of ru... more This study presents cross-sectional data from an ongoing mixed-longitudinal study of growth of rural children from Ellisras, South Africa. The physical growth and nutritional status of 1,335 children (684 boys, 651 girls), 3-10 years of age, was determined using standard anthropometric techniques. Weight-for-age, height-for-age, and weight-for-height were expressed as Z-scores of the NHANES I and II or NCHS reference sample. A Z-score of less than −2 was used as the cut-off point to determine the prevalence of stunting and wasting. Mean heights increased parallel to the 50 th centile up to 6 years of age, thereafter both sexes diverged from the NHANES reference by approximately 0.5 cm per year. Mean weights followed a more consistent pattern from 3-7 years for both sexes, which was parallel to just below the 10 th centile, but diverged between 8 and 10 years of age. Z-scores of weight-for-height in both sexes varied between −1 to −2 throughout the age range and BMI values were lower than the 5 th centile of NHANES, indicating a significant amount of wasting within the sample. The sample exhibited a high prevalence of stunting, rising from less than 10% at 7 years to more than 30% by 10 years of age. Increments of the mean heights and weights indicate that the effects of stress may be a gradually accumulating process and that the growth increments of these children became increasingly poor in contrast to those of the reference sample. Since stunting in childhood is permanent, it may lead to a loss of physical work capacity in adulthood. Therefore, further investigation of the cause of poor growth among these rural children is imperative. Am.

International Journal of Obesity, 1997

OBJECTIVE: To investigate the prevalence and gender differences in obesity in rural African adole... more OBJECTIVE: To investigate the prevalence and gender differences in obesity in rural African adolescents. DESIGN: Cross-sectional analysis of a mixed-longitudinal study. SUBJECTS: Four hundred and forty-seven rural African adolescents (190 females; 257 males) aged 7.0±18.9 y. MEASUREMENTS: Anthropometric measurements of height, weight, and skinfolds at the bicep (BCP), tricep (TRCP), subscapular (SSCP) and suprailiac (SPIL) sites and derived ratios of fat distribution including trunk:limb ratios (SSTB (SSCP SPIL)/(TRCP BCP) and ST SSCP/TRCP), and the upper:lower truncal ratio (TRUNK SSCP/SPIL). Obesity was de®ned as (1) a BMI greater than the NHANES III 85% centile or (2) the sum of TRCP and SSCP skinfolds greater than the NHANES III 85% centile. RESULTS: Skinfold measures were signi®cantly greater in females throughout the age range but remarkably greater divergence was apparent after mean menarcheal age of 14.03 y (s.d. 1.25). Centralization of body fat was consistently greater in males but only signi®cantly so after 14 y of age for the ST ratio. Obesity, de®ned by BMI or sum of skinfolds, was greatest in females following menarche reaching a maximum of 16.7% by BMI and 11.1% by sum of skinfolds, and almost non-existent in males. CONCLUSIONS: Increased prevalence of obesity in African females did not occur throughout adolescence but was linked to the timing of menarche. Increased fatness and obesity appears to be a post-menarcheal phenomenon probably caused by the hormonal changes leading to and following ®rst menstruation.

Economics & Human Biology, 2003

The economic transition in developing countries is not always the result of the change from a cen... more The economic transition in developing countries is not always the result of the change from a centrally-planned to a free-market economy, but may be found within an already existing free-market economy as a result of profound political change, as in South Africa. The release of Nelson Mandela in February 1990 heralded an end both to the political system of apartheid and to the concomitant social, political, and economic disenfranchisement of 30 million non-White people in South Africa. The first freely elected non-White government came to power in 1994 and initiated a number of social and economic reforms aimed at alleviating the worst consequences of apartheid. This paper examines the effect of post-apartheid economic and social transition on the growth and development of urban children. Over 4000 children born in Soweto and Johannesburg were enrolled in the Birth to Ten (BTT) birth-cohort study in 1990. Whilst these children were born with lower birth weights than in developed countries, they did grow strongly in infancy, particularly in weight, to reflect normal reference values for body mass index (BMI) by 1 year of age. While post-apartheid social and economic changes were expected to take some time to affect child growth and development, the rate of change has been slower than expected. Data from the BTT study demonstrate that the growth of White children continues to be superior to that of their non-White peers and differences that existed at birth and during infancy have not diminished during childhood and early adolescence. Whatever factors are changed at the national or community levels during economic (and social) transition in South Africa appear not yet to have resulted in improved child physical growth.

Human Biology, 2004

Telomeres are noncoding functional DNA repeat sequences at the ends of chromosomes that decrease ... more Telomeres are noncoding functional DNA repeat sequences at the ends of chromosomes that decrease in length by a predictable amount at each cell division. When the telomeres become critically short, the cell is no longer able to replicate and enters cellular senescence. Recent work has shown that within individuals, telomere length tracks with cardiovascular health and aging and is also affected by growth variation, both prenatally and postnatally. Therefore telomere length can be a marker of both growth history (cell division) and tissue function (senescence). Relationships between early growth and later health have emerged as a research focus in the epidemiology of chronic diseases of aging, such as heart disease and diabetes. The "fetal origins" literature has demonstrated that hormonal and nutritional aspects of the intrauterine environment not only affect fetal growth but also can permanently alter the metabolic program of the individual. Smaller infants tend to have a higher risk of developing cardiovascular disease. Much less attention has been paid to possible genetic links between the processes of early growth and later disease. Our aim in this review is to summarize evidence for one such genetic mechanism, telomere attrition, that may underlie the fetal origins of cardiovascular disease and to discuss this mechanism in light of the evolution of senescence.

Annals of Human Biology, 1992

... It is traditionally accepted in southern Africa that Zulus are larger than other 'tribal... more ... It is traditionally accepted in southern Africa that Zulus are larger than other 'tribal' groups but this anecdote is not born out by the lack of significant differences in height between the Zulu and Northern Sotho/Pedi children. Differences ...

American Journal of Physical Anthropology, 1994

Adolescent growth in height, fatness, and fat patterning was investigated in a sample of 79 rural... more Adolescent growth in height, fatness, and fat patterning was investigated in a sample of 79 rural South African black children studied longitudinally from 6–18 years. Data were analyzed relative to peak height velocity (PHV) to identify the phenomenon of “compensatory” growth in height during adolescence and to describe changes in fatness and fat patterning. Compensatory growth following PHV was clearly observed relative to NHANES data for African-Americans in that Z-scores for height at the start of the adolescent growth spurt were greater than those at the end of the spurt. Statistically significant differences in fatness and centralization between males and females did not occur until about 2 years after PHV was attained. Centralization of fat occurred in both sexes but moreso in males. The lack of centralization in females was due to relatively greater triceps skinfold velocities. The rapid gain in post-PHV fatness in females may represent a physiological adaptation to an energetically sub-optimal environment, buffering the energetic costs of reproduction. © 1994 Wiley-Liss, Inc.

American Journal of Human Biology, 1991

Age at menarche was estimated using status quo techniques on a sample of 230 rural South African ... more Age at menarche was estimated using status quo techniques on a sample of 230 rural South African females aged 11 to 17 years. Mean age of menarche was 14.03 years (SD = 1.25 years). Compared with contemporary rural and well-off urban samples, these females experienced menarche 0.6 years earlier than did the rural sample and 0.8 years later than the well-off urban group. Data from 11 previously reported studies of menarcheal age in urban and rural girls were analyzed with these data to determine the existence and magnitude of secular trends and whether rates differed between urban and rural environments. Regression analysis demonstrated a clear secular trend in both urban and rural females since 1943. Menarcheal age decreased at a rate of 0.34, 0.73, and 0.46 years per decade for rural, urban, and combined groups, respectively. The decline in menarcheal age over the last 40 years is thought to be due to improving socioeconomic conditions, but differences between urban and rural groups remain. Within rural groups there appears to be considerable variation in menarcheal age.

Annals of Human Biology, 1996

Intergenerational and socioeconomic effects on menarcheal age were investigated in a sample of 14... more Intergenerational and socioeconomic effects on menarcheal age were investigated in a sample of 146 mother-daughter pairs of South African Indians living in the urban area of Lenasia, Gauteng Province. Information on menarcheal age, socioeconomic status, and educational attainment of both parents was obtained by questionnaire. Data on menarcheal age of daughters were analysed by probit analysis and descriptive statistics. Mean maternal menarcheal age was 13.20 years (SD = 1.57) and was significantly greater than the menarcheal age of the postmenarcheal daughters at 12.52 years (SD = 1.25) and of mean menarcheal age analysed by probits of 12.40 years (SD = 1.18). Mother-daughter menarcheal ages were significantly correlated (r = 0.23; p < 0.035). This association was confounded by the significant association of maternal menarcheal age to the age at which mothers recalled that event (r = 0.32; p < 0.003). Partial correlations demonstrated that the mother-daughter correlation reduced to a non-significant 0.16 (p < 0.14) after maternal age at recall had been controlled. No significant associations were found between socioeconomic variables and menarcheal age except for family size, in which girls with more than three siblings had significantly later menarcheal ages than girls with three siblings. Secular trends for reduced menarcheal ages were evident in both the intergenerational data (0.24 years/decade) and in comparison to the data of Kark (1953) from four decades ago (0.27 years/decade).

American Journal of Human Biology, 1992

Growth status, body fatness, and fat patterning were investigated in two cross-sectional samples ... more Growth status, body fatness, and fat patterning were investigated in two cross-sectional samples of rural South African Black children 6–19 years of age. The results were compared to data for American Blacks who were part of the NHANES survey. The two South African samples differed consistently, although rarely significantly, but both were smaller, lighter, and less fat than American Blacks. Analyses of triceps, biceps, subscapular, and suprailiac skinfolds demonstrated that all three samples had similar fat patterning when analysed either by investigating the Centripetal Fat Ratio or through an analysis of principal components. Following correction for general fatness, and in common with other studies of fat patterning, the first component related to central-peripheral patterning, the second to a ventral-dorsal patterning, and the third to upper-lower body patterning. These three components accounted for 99.4% of the total variance. It is suggested that central-peripheral fat patterning is a species characteristic but that other patterns are individual characteristics. Analysis of principal components within childhood, pre-adolescent and adolescent age groups suggested that prior to adolescence a negative relationship exists between absolute level of fatness and centralization such that thinner, less fat, children are more centralized. During adolescence, however, there is no relationship between level of fatness and centralization. © 1992 Wiley-Liss, Inc.

Annals of Human Biology, 1993

The timing and duration of secondary sexual development in two samples of rural and urban South A... more The timing and duration of secondary sexual development in two samples of rural and urban South African black children were investigated using the Tanner staging techniques and compared to similar data from Switzerland and England. In general rural black children were consistently delayed in the age at which they entered the events of puberty, and took longer to pass through each of the stages. Urban black children, from good socioeconomic backgrounds, were advanced in relation to their rural peers and slightly ahead of the European samples. There were no significant differences in the sequence of events. Estimates of testicular volume on the well-off urban boys demonstrated that they exhibited similar volumes to European boys at similar ages. It is suggested that the British clinical longitudinal growth standards could be effectively used to sensitively monitor the growth and maturation of black urban children from good socioeconomic backgrounds.