LONGITUDINAL GROWTH PARAMETERS AND THEIR ECOLOGICAL DETERMINANTS (SEASONALITY)

The growth patterns of weight from birth through the first twelve months of life among rural Taiwanese infants were investigated with the following objectives: (i) compare each of the parameters of the Count model estimated for infants who were nutritionally at risk with those for a reference population from the United States; and (ii) within the Taiwanese infants, account for the variance in the growth patterns in the first and second six months of life on the basis of selected ecological factors.^ The significance between group differences were observed in the patterns of the weight growth in both linear growth and in the timing and the direction of velocity changes. A significant decline in growth velocity was observed among Taiwanese infants at about the fourth month of life. The decline is in keeping with a recent proposal made by J. C. Waterlow regarding the timing of change in growth velocity among nutritionally at risk populations in developing countries. The growth course of a nutritionally at risk infant during the first three months is apparently protected by the nurturance of the mother and innate biological properties of the infant.^ A highly significant portion of the growth variance in the second six months of life was accounted for by exogenous factors and biological factors related to the infant. Conversely, none of the growth variance in the first six months of life was accounted for by predictor variables. The most potent determinant of growth in the second six months of life was seasonality which represents a multiple environmental event.^ The model parameters estimated from the Count model represent different aspect of physical growth; yet the correlation coefficients between parameters b and c are high (r > .80). Clearly, the biological interpretation of the model parameters requires analysis of the whole function in the specific context of a given age period. ^

Seasonality of respiratory syncytial virus infection in Texas

Respiratory syncytial virus (RSV) is a common cause of respiratory infection in infants and children that can result in bronchiolitis or pneumonia. Each year in the United States, it causes up to 400 deaths and 125,000 hospitalizations among children less than one year of age. RSV is transmitted by direct or close contact with contaminated secretions, which may involve droplets and fomites. Monthly administration of a monoclonal RSV antibody, palivizumab (Synagis™, MedImmune, Gaithersburg, MD), in premature infants, infants with chronic lung disease, or congenital heart disease has been shown to significantly reduce the risk of severe RSV infection. The Centers for Disease Control and Prevention's (CDC) National Respiratory and Enteric Virus Surveillance System (NREVSS) is a laboratory based passive reporting system that collects state, regional, and national RSV data. The CDC defines the RSV season onset as “the first of 2 consecutive weeks during which the mean percentage of specimens testing positive for RSV antigen is 10%.” RSV season offset is defined as the last of 2 consecutive weeks during which the percentage of positive specimens is less than or equal to 10%. Annual RSV epidemics generally occur during the winter and early spring months, but the RSV season is known to vary by national regions. Precise delineation of the RSV epidemiology by region could maximize protection from RSV and minimize the cost of RSV immune prophylaxis. ^ The purpose of this thesis is to define the RSV season in Texas over time; compare the RSV season of the state of Texas and its regions with the national norms; and to compare RSV seasonality between the various regions in Texas. ^ This study was a retrospective analysis of data reported to NREVSS to evaluate potential disparities in the onset weeks, offset weeks, and duration of the annual RSV season in Texas. Data were collected from 70 reporting sites, and includes information from the 2004–2005 to 2009–2010 RSV seasons. ^ The observed median onset (week 44) and offset week (week 8) for the Texas were consistent with national estimates for the South. Regional estimates and statistical analysis suggested that the RSV season in Texas would be better represented by regions. Regional seasonal comparisons revealed considerable variation in season offset and duration between many of the geographic regions within Texas. This trend should be studied further.^

Environmental and behavioral risk factors for moderate or severe rotavirus diarrhea in children less than 24 months

On a global basis rotaviruses are the most important agents involved in childhood diarrhea. In developing countries they account for 6% of all diarrheas and 20% of all diarrhea related deaths of children under 5 years of age, with over 1 billion episodes and over 4 million deaths annually. Given the disease burden, there is a need for better understanding the risk factors involved in rotavirus disease, to identify areas of intervention. In order to provide this information, two areas were developed: a review of the literature, examining the causal evidence for rotavirus diarrhea and a case comparison study. The case comparison study analyzed two areas: identifying climate factors and, identifying environmental and behavioral risk factors. The literature review showed that few analytical studies have identified specific risk factors such as home environment, and a winter seasonal trend for temperate areas, but in key areas evidence is contradictory. The case comparison study for climate factors demonstrated that seasonality occurs in a tropical country like Venezuela and that a complex interplay between weather conditions contribute to the seasonal pattern. A positive association between rain fall (OR 4.1); dew point (OR 2.3) and temperature differential during the day (OR 1.4) and, an inverse association with temperature (OR 0.5) and relative humidity (OR 0.8) was found. This information is useful in understanding the seasonal pattern of rotavirus and for planning health care needs. The second analysis demonstrated that environmental variables such as crowding (OR 14.3), contact with someone with an infectious disease (OR 4.9) and animal ownership (OR 2.3) were important. Restricting the analysis to animal owners demonstrated that living In a rural settling (OR 13.8), defecating in inappropriate places (OR 7.2), crowding(4.2) and indoor animals (4.0) are of importance. Behavioral variables identified were: lack of breast feeding (OR 4.0) and visiting when someone was sick (OR 3.4). Biological and demographic variables of importance were: age, with a dose response relationship; undernurishment (OR 11.3) and household per capita monthly income less than US $ 16.30 (OR 8.5). Using a diarrhea compeer group we found that, although some of the previous variables were of importance, no major differences were found. These findings are important in identifying paths for prevention and further research. ^

Evaluation of residential bioaerosol concentrations and their related health effects

Limited research has been conducted on the collection of bioaerosols and their health effects on individuals in the El Paso area. A year long study was conducted in the region to evaluate indoor bioaerosol concentrations (Mota et al., unpublished data). As part of the study, air samples were collected during each season for a year from 38 homes from the El Paso area. The main objective of the study was to assess seasonality differences in bioaerosol concentrations. The air samples were then cultured and analyzed for bacterial and fungal concentrations. As a supplement to that study, a health questionnaire was given during each seasonal air sampling to the participating resident to complete regarding their health status. The aim of this study was to evaluate the health questionnaire and assess any associations between the collected bioaerosol concentrations and the self-reported respiratory symptoms of the participating home residents. Symptom frequencies were tabulated and basic descriptive statistics, along with logistic regressions, were conducted on the relationship between “High” reporters of symptoms and bioaerosol concentrations and environmental factors. The most commonly reported symptoms by homeowners were nasal symptoms and allergies. In addition, there was evidence to support an association between indoor respirable bacteria concentrations and homeowners that report greater than or equal to 8 respiratory symptoms (OR=1.10, p=0.045). Smoking status, indoor humidity and season also displayed associations with homeowners that report greater than or equal to 8 respiratory symptoms (OR=3.3, p=0.045; OR=71.0, p=0.030; OR=7.2, 3.2, p=0.001, 0.008). With such a strong association, future assessment of symptoms, bioaerosol concentrations and environmental factors is needed to further establish their relationship. ^

Factors affecting ozone related asthma responses among middle school students with asthma

Outdoor environmental risk factors for asthma have been extensively researched, even though the majority of a person's daily activity occurs indoors. There is limited evidence linking personal exposure concentrations of ozone, pollen, mold, temperature, and humidity to childhood asthma. ^ The current study consisted of a secondary, more complex analysis of the data from the Houston Air Toxics and Asthma in Children (ATAC) Study to further investigate the association of personal ozone exposure on asthma outcome variability among middle school children with asthma. The ATAC Study primarily investigated the association between selected oxygenated air toxics and indicators of asthma variability (PEFR, FEV1, asthma symptoms, and rescue medication usage) among 30 labile and persistent Houston middle-school children with diagnosed asthma. This panel study used a repeated measurements design of four separate 10-day sampling periods that extended over a 20 month period. The secondary analysis included aggregate regression models that were constructed with two different estimates of ozone exposure (daily maximum hourly outdoor concentration and daily maximum hourly personal exposure), with three different estimates of personal environmental temperature and humidity exposures (daily average, intraday difference, and interday difference), and for thee different time periods [same day of exposure (lag 0), one day after initial exposure (lag 1), and two days after initial exposure (lag 2)]. ^ Overall, the models using daily maximum hourly personal ozone exposures in combination with intraday and interday personal temperature and humidity differences produced more significant plausible associations than models using daily maximum hourly personal ozone exposures with personal average temperature and humidity exposures. Significant associations were identified between daily maximum hourly personal ozone exposure and clinical indicators of asthma variability. The increasing effect on rescue medication usage from daily maximum hourly personal ozone exposure were identified as soon as the same day of exposure (lag 0; p=0.0072), and the same effects were delayed until the second next day (lag 2; p= 0.0026). The increasing effect on asthma symptoms were identified on the second next day after initial exposure (lag 2; p= 0.0024). There was a consistent inverse relationship between personal relative humidity exposure and indicators of asthma variability. Decreasing effects on daily FEV1 variability from personal relative humidity exposure were identified on the same day of exposure (lag 0; p= 0.034), increasing effects on morning PEFR were identified on the next day after initial exposure (lag 1; p= 0.0001), and decreasing effects on overnight PEFR variability were identified on the second next day after the initial exposure (lag 2; p= 0.007). With the conclusion of this research, there are opportunities for future similar studies in the preventive management of asthma in children living in high-ozone areas.^

The chronobiology of the menstrual life sequence of American women

Seasonal variation in menarche, menstrual cycle length and menopause was investigated using Tremin Trust data. Too, self-reported hot flash data for women with natural and surgically-induced menopause were analyzed for rhythms.^ Menarche data from approximately 600 U.S. women born between 1940 and 1970 revealed a 6-month rhythm (first acrophase in January, double amplitude of 58%M). A notable shift from a December-January peak in menarche for those born in the 1940s and 1950s to an August-September peak for those born in the 1960s was observed. Groups of girls 8-14 and 15-17 yr old at menarche exhibited a seasonal difference in the pattern of menarche occurrence of about 6 months in relation to each other. Girls experiencing menarche during August-October were statistically significantly younger than those experiencing it at other times. Season of birth was not associated with season of menarche.^ The lengths of approximately 150,000 menstrual intervals of U.S. women were analyzed for seasonality. Menstrual intervals possibly disturbed by natural (e.g., childbirth) or other events (e.g., surgery, medication) were excluded. No 6- or 12-month rhythmicities were found for specific interval lengths (14-24, 25-31 and 32-56 days) or ages in relation to menstrual interval (9-11, 12-13, 15-19, 20-24, 25-39, 40-44 and 44 yr old and older).^ Hot flash data of 14 women experiencing natural menopause (NM) and 11 experiencing surgically-induced menopause (SIM) did not differ in frequency of hot flashes. Hot flashes in NM women exhibited 12- and 8-hr, but not 24-hr rhythmicities. Hot flashes in SIM women exhibited 24- and 12-hr, but not 8-hr, rhythmicities. Regardless of type of menopause, women with a peak frequency in hot flashes during the morning (0400 through 0950) were distinguishable from those with such in the evening (1600 through 2159).^ Data from approximately 200 U.S. women revealed a 6-month rhythm in menopause with first peak in May. No significant 12-month variation in menopause was detected by Cosinor analysis. Season of birth and age at menopause were not associated with season of menopause. Age at menopause declined significantly over the years for women born between 1907 and 1926, inclusive. ^