Kenneth L. Campbell

Traffic Accident involvement rates by driver age and gender

Passenger-vehicle travel data from the 1990 Nationwide Personal Transportation Survey were combined with crash data from the 1990 Fatal Accident Reporting System and the 1990 General Estimates System to produce crash involvement rates per vehicle-mile of travel. Elevated rates were observed for drivers aged 16-19 and 75 and over. The oldest drivers had the highest fatal involvement rate, while the youngest drivers had the highest rate of involvement in all police-reported crashes. Men had a higher risk than women of experiencing a fatal crash, while women had higher rates of involvement in injury crashes and all police-reported crashes.

Fertility in Traditional Societies

This chapter is a preliminary attempt to characterise reproductive patterns in traditional, pre-industrial societies, including huntergatherers, tribal horticulturalists and pastoralists and settled peasant agriculturalists. Assertions about the level of fertility in such societies have played a key role in the development of theoretical models in demography and anthropology and, more recently, in reproductive biology. In classic demographic transition theory, for example, it was assumed that pre-transitional societies were characterised by uniformly high fertility rates, which provided the starting point for the recent secular decline in fertility (Knodel, 1977). Most ecological anthropologists, in contrast, have come to believe that many traditional societies, especially unacculturated hunter-gatherers, have regulated their reproductive output at relatively low levels (Dumond, 1975; Peacock, 1986). It has even been suggested that there occurred an earlier, stone-age demographic transition toward higher. birth and death rates associated with the emergence of settled village life during the Neolithic (Handwerker, 1983; Roth, 1985).1

Urinary Estrone Conjugate and Pregnanediol 3-Glucuronide Enzyme Immunoassays for Population Research

BACKGROUND Monitoring of reproductive steroid hormones at the population level requires frequent measurements, hormones or metabolites that remain stable under less than ideal collection and storage conditions, a long-term supply of antibodies, and assays useful for a range of populations. We developed enzyme immunoassays for urinary pregnanediol 3-glucuronide (PDG) and estrone conjugates (E1Cs) that meet these criteria. METHODS Enzyme immunoassays based on monoclonal antibodies were evaluated for specificity, detection limit, parallelism, recovery, and imprecision. Paired urine and serum specimens were analyzed throughout menstrual cycles of 30 US women. Assay application in different populations was examined with 23 US and 42 Bangladeshi specimens. Metabolite stability in urine was evaluated for 0-8 days at room temperature and for 0-10 freeze-thaw cycles. RESULTS Recoveries were 108% for the PDG assay and 105% for the E1C assay. Serially diluted specimens exhibited parallelism with calibration curves in both assays. Inter- and intraassay CVs were <11%. Urinary and serum concentrations were highly correlated: r = 0.93 for E1C-estradiol; r = 0.98 for PDG-progesterone. All Bangladeshi and US specimens were above detection limits (PDG, 21 nmol/L; E1C, 0.27 nmol/L). Bangladeshi women had lower follicular phase PDG and lower luteal phase PDG and E1Cs than US women. Stability experiments showed a maximum decrease in concentration for each metabolite of <4% per day at room temperature and no significant decrease associated with number of freeze-thaw cycles. CONCLUSIONS These enzyme immunoassays can be used for the field conditions and population variation in hormone metabolite concentrations encountered in cross-cultural research.

Lactation and birth spacing in highland New Guinea.

The effects of infant suckling patterns on the post-partum resumption of ovulation and on birth spacing are investigated among the Gainj of highland New Guinea. Based on hormonal evidence the median duration of lactational anovulation is 20.4 months accounting for about 75% of the median interval between live birth and next successful conception (i.e. resulting in live birth). Throughout lactation suckling episodes are short and frequent the interval changing slowly over time from 24 minutes in newborns to 80 minutes in 3-year olds. Maternal serum prolactin concentrations decline in parallel with the changes in suckling patterns approaching the level observed in non-nursing women by about 24 months postpartum. A path analysis indicates that the interval between suckling episodes is the principal determinant of maternal prolactin concentration with time since parturition affecting prolactin secretion only in so far as it affects suckling frequency. The extremely prolonged contraceptive effect of breastfeeding in this population thus appears to be due to 1) a slow decline in suckling frequency with time since parturition; and 2) absence of a decline over time in hypothalamic-pituitary responsiveness to the suckling stimulus. (authors modified)

Demographic and endocrinological aspects of low natural fertility in highland New Guinea

The Gainj of highland Papua New Guinea do not use contraception but have a total fertility rate of only 4.3 live births/woman, 1 of the lowest ever recorded in a natural fertility setting. Reproductive and marital histories were obtained from 305 females and 206 males aged 10+. Each subject was asked about: number of live born offspring ever produced; number of stillbirths ever produced; number and names of offspring currently being nursed; number of current and past spouses; and the cause of dissolution of all past marriages. Blood samples were drawn from 172 volunteer female subjects aged 10-60 years and ovarian function was classified by concentration of progesterone. From an analysis of these cross-sectional demographic and endocrinological data, the causes of low reproductive output have been identified in women of this population as: late menarche and marriage, a long interval between marriage and 1st birth, a high probability of widowhood at later reproductive ages, low effective fecundability and prolonged lactational amenorrhea. These are combined with near-universal marriage, and a low prevalence of primary sterility similar to that found in other populations. Of all the factors limiting fertility, by far the most important are those involved in birth spacing, especially lactational amenorrhea. The effects of widowhood on Gainj fertility are negligible. Factors acting to lower fertility fall into 2 categories: those that determine the age of onset of reproduction and those that act to space births. Given the observed pattern of birth spacing, however, the delay in commencement of reproduction represents on average no more than 1 or 2 live births averted/woman. In contrast, were age at 1st reproduction held constant while reducing birth intervals to a mean of 2.0-2.5 years, total fertility would increase to about 7 or 8. Future research on natural fertility should focus on specific behavioral and physiological mechanisms governing the reproductive process.

Fatal accident involvement rates by driver age for large trucks

Survey data on large trucks involved in fatal accidents and on the travel of large trucks provide estimates of fatal accident involvement rates by driver age. The analysis is focused on the implications of lowering the minimum age for drivers of commercial trucks operating interstate from 21 to 19 years. Fatal accident involvement rates for drivers of large trucks are found to increase with decreasing driver age. The younger drivers are over-involved until about age 27. Drivers under the age of 21 are over-involved by a factor of 6 in comparison to the overall rate for all drivers. Other factors known to have significant influences on the probability of involvement in a fatal accident were examined to determine their association with the over-involvement of younger drivers. The general pattern of over-involvement for younger drivers pervades virtually every combination of factors examined. Thus, it is concluded that the basic trend with driver age shown in the aggregate data is primarily associated with age and is not associated with the other factors examined. The results of this analysis substantiate an elevated risk of fatal accident involvement for younger drivers of large trucks.

Accident rates for heavy truck-tractors in Michigan

Accident rates of heavy truck-tractors are modelled using log-linear methods. The accident data used are a census of truck-tractor involvements in Michigan from May 1987 to April 1988. Travel data used to calculate the rates were produced by a survey of truck-tractors in Michigan covering the same time period. Both the accident and travel data were limited to Michigan-registered tractors operating in Michigan. Log-linear models of casualty and property-damage-only accident rates were developed using number of trailers, road type, area type, and time of day as predictor variables. Overall, differences between tractors with one and two trailers were not significant. Tractors with no trailers (bobtails) have significantly higher accident rates. Characteristics of the operating environment were found to have larger effects on the accident rate than tractor configuration (except for the bobtail). Rates varied by a factor of up to 6.8, depending on the road type. Casualty accident risk at night was 1.4 times the risk during the day. The risk of a casualty accident in rural areas was 1.6 times that of urban areas.

Energy reserves and parity of nomadic and settled Turkana women

Members of the Turkana tribe include settled and nomadic peoples who reside in the southern part of Turkana District in the semiarid region of northwest Kenya. Nomadic Ngisonyoka Turkana keep livestock (camels, cattle, sheep, goats, donkeys), subsist principally on livestock products, and move camps frequently in search of forage for the livestock; settled Turkana cultivate foods along the principal rivers. Both nomadic and settled Turkana are subject to limited food resources on seasonal and long‐term bases. Protein from meat, blood, and milk is sufficient in the diet, but food energy is limited, as are body fat reserves. Previous work has documented a decline in maternal adiposity with age in a large sample of the relatively lean nomadic women, and a negative association of fat stores with parity in a smaller sample of nomadic women. The problem of maternal depletion of fat energy reserves as a function of female reproductive history is explored in this study through anthropometry in a relatively large sample (N = 312) of nomadic and settled women. Both nomadic and settled women displayed some parity‐related losses in fat stores. The relationship was stronger in the nomads, even after controlling for age.

American Adolescents and Music Videos: Why Do They Watch?

In August 1981 the Music Television network began airing rock music videos 24-hours a day to cable subscribers across the United States. The videos were 3-5 minute long visual depictions set to music and usually featured band members either performing the music or acting out roles suggested by the lyrics and music. By the end of 1984 one quarter of American households with televisions were viewing the MTV channel.’ I Eighty three percent of the target audience, 18-to-34year-olds, were watching an average of one hour during the day and

Statistical Correction for Non‐parallelism in a Urinary Enzyme Immunoassay

Abstract Our aim was to develop a statistical method to correct for non‐parallelism in an estrone‐3‐glucuronide (E1G) enzyme immunoassay (EIA). Non‐parallelism of serially diluted urine specimens with a calibration curve was demonstrated in an EIA for E1G. A linear mixed‐effects analysis of 40 urine specimens was used to model the relationship of E1G concentration with urine volume and derive a statistical correction. The model was validated on an independent sample and applied to 30 menstrual cycles from American women. Specificity, detection limit, paral‐lelism, recovery, correlation with serum estradiol, and imprecision of the assay were determined. Intra‐and inter‐assay CVs were less than 14% for high‐ and low‐urine controls. Urinary E1G across the menstrual cycle was highly correlated with serum estradiol (r = 0.94). Non‐parallelism produced decreasing E1G concentration with increase in urine volume (slope = −0.210, p < 0.0001). At 50% inhibition, the assay had 100% cross‐reactivity with E1G and 83% with 17β‐estradiol 3‐glucuronide. The dose–response curve of the latter did not parallel that of E1G and is a possible cause of the non‐parallelism. The statistical correction adjusting E1G concentration to a standardized urine volume produced parallelism in 24 independent specimens (slope = −0.043 ± 0.010), and improved the average CV of E1G concentration across dilutions from 19.5% ± 5.6% before correction to 10.3% ± 5.3% after correction. A statistical method based on linear mixed effects modeling is an expedient approach for correction of non‐parallelism, particularly for hormone data that will be analyzed in aggregate.