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Biomedical subjects

E B Hook

Publications and source records attributed to E B Hook.

At least 163 records · Page 9Linked to original sources
PubMed1980

On the inadequacy of quinquennial data for analyzing the paternal age effect on Down's syndrome rates.

Investigations of the influence of paternal age on the rate of Down's syndrome are complicated by the high correlation between parental ages and the strong dependence of the incidence rate upon maternal age. Two possible approaches to isolating an independent paternal age effect are shown to lead to erroneous results if based on data by quinquennial age intervals rather than by single-year intervals. For a multiple regression method the discrepancy can be removed by using the mean maternal and mean paternal age within each quinquennial cell. Failure to do so results in an artifactual paternal age effect.

Down Syndrome↗
PubMed1980

Rates of Down's syndrome at the upper extreme of maternal age--absence of a "leveling" effect and evidence for artifacts resulting from analyses of rates by five-year maternal age intervals.

A "leveling" in the first order exponential increase of the rate of Down's syndrome with maternal age over 40 years of age has been suggested by others in review of data reported by five-year maternal age interval. In contrast, data reviewed here analyzed by one-year interval reveal no evidence for such an effect when the observed rates (O) at each maternal age in the 40--49-year age range and in the 45--49-year age range are compared with those predicted (P) from first order exponential equations derived from data in the 33--44-year age range. The sign of O -- P is not predominantly negative as would be expected if there were a "leveling" effect. Part of the evidence for leveling in previous studies may derive from the fact that rates have been plotted at the midpoints of the intervals rather than at the true mean maternal ages of mothers having births in these five-year intervals. It is shown that in the three data sources considered here, the difference between the quin-quennial mean maternal age and the interval midpoint is greater at older ages than at younger ages. Thus, plotting rates at the midpoint of five-year intervals results in significant graphic underestimate of the rates, and may result in a slight leveling effect. It is suggested that selective underascertainment of births to those in the older maternal ages in previous studies may also have contributed to the leveling effect observed earlier.

Adult↗
PubMed1980

A search for evidence for a paternal age effect independent of a maternal age effect in birth certificate reports of Down's syndrome in New York state.

The discovery that in 20% to 30% of Down's syndrome cases the extra chromosome is of paternal origin, and the recent independent report of two groups that maternal age-specific rates are two-fold greater for livebirths to couples in which the father is aged 55 years and over prompted this investigation. Analyses were of coded birth certificate reports of Down's syndrome in Upstate New York residents in the years 1963-1974. The expected numbers of cases, on the assumption of no paternal age effect, were determined at each paternal age interval (and at each paternal age minus maternal age interval) adjusting for an effect of maternal age; these were compared with observed values. There was a slightly lower number of observed than expected cases for fathers aged 55 years and over (ratio = 0.76), and the results exclude with 95% confidence an increase of 1.5-fold or greater in rates in this group after correction for maternal age. There was, moreover, no overall evidence for any trend to increasing rates with paternal age. Regression analyses in which the data were first fit to functions of maternal age and subsequently terms involving paternal age were introduced also revealed no evidence that paternal age made a significant independent contribution to the observed rates in contrast to the conclusion of earlier positive reports.

Adolescent↗
PubMed1980

Use of Bernoulli census and log-linear methods for estimating the prevalence of spina bifida in livebirths and the completeness of vital record reports in New York State.

Data from birth certificates (BC), death certificates (DC) and medical rehabilitation files (MR) were analyzed to estimate the livebirth prevalence of spina bifida in upstate New York in 1969-1974 and the completeness of the data sources. Birth certificates listed about 68% of cases, death certificates about 27% and medical rehabilitation files about 25%. The three sources together, it is estimated, included only about 80% of cases in the population. For each source, comparisons of estimates of completeness derived using each of the other two as reference sources were found to be useful for evaluating the likelihood of source dependence. The estimated livebirth prevalence rate, adjusting for incomplete reporting and the observed negative dependence of MR and DC sources, was 0.85 per 1000 livebirths by both Bernoulli census and log-linear methods. Taking into account in addition evidence for a BC-DC positive dependence, the resulting prevalence rate estimates were slightly higher, 0.88 per 1000 by log-linear methods and 0.90 per 1000 by the Bernoulli census approach. In view of the likely BC-DC positive dependence, it is suggested that Bernoulli census estimates derived using only these two sources without some ancillary third data source are likely to be biased to a false low figure. Nevertheless, estimates from BC and DC alone may still be useful in establishing that the prevalence rate is above some minimum figure, for example a "breakeven" prevalence rate, in cost-benefit analyses of a possible prevention program.

Birth Certificates↗
PubMed1980

Estimates of the likelihood that a Down's syndrome child of unknown genotype is a consequence of an inherited translocation.

The proportions of Down's syndrome livebirths associated with a Robertsonian translocation inherited from a carrier parent were estimated from data in the New York State Chromosome Registry and in two previous publications. Indirect estimates were made in each 5-year maternal age interval; these were derived from mutation rates for these translocations and maternal age specific prevalence rates in livebirths. The proportions diminished steadily with increasing maternal age. The ranges for the seven maternal age groups from under 20 to 45 to 49 were: 1.1 to 2.8%, 1.0 to 2.7%, 0.7 to 1.8%, 0.5 to 1.3%, 0.2 to 0.4%, 0.05 to 0.1%, and 0.02 to 0.04%. Direct estimates from the observed data could only be attempted for two age groups, women under 30 and those 30 or more. For those under 30 the range in proportions was 0.9 to 1.9% and for those 30 and over, 0.2 to 0.4%. In general the lowest proportions at any age were derived from New York State data and the highest from Japanese data.

Adult↗
PubMed1980

A simple function for maternal-age-specific rates of Down syndrome in the 20-to-49-year age range and its biological implications.

The familial increase in the rate of Down syndrome with maternal age can be represented by a simple equation, consisting of the sum of a constant term plus an exponential term that is a first-order function of masternal age: y = a + exp (b + cx), where y is the rate in live births, x is maternal age, and a, b, and c are constants. Unlikely analyses in which two separate equations were derived from different segments of the 20 to 49 maternal age range, this single, simple equation can be applied to the entire range. An unlike previous complex equations that were derived by regression analysis for the entire age range, the component terms can be readily understood as contributions by different etiologic categories. This model fits the data recently available by 1-year intervals about as well as the approach that used separate equations, but it has fewer parameters and requires no ad hoc division of the age range. However, it does not postulate a sharp transition in biological processes around maternal age 30, but, rather, a process continuously accumulating at a constant exponential rate (analogous to that produced by an infectious mechanism), superimposed upon a constant background rate.

Adult↗
PubMed1980

Influence of pregnancy on dietary selection.

Three interrelated symptom ' complexes' are implicated in dietary changes during pregnancy: nausea and vomiting of pregnancy (NVP), dietary aversions, and dietary cravings. These are discussed with particular emphasis on NVP and the fate of the fetus.

Diet↗
PubMed1980

Rates of 47, + 13 amd 46 translocation D/13 Patau syndrome in live births and comparison with rates in fetal deaths and at amniocentesis.

Trisomy 13 (Patau syndrome) is rare in newborns. Data on rates in 167,774 live births from 17 separate studies are reviewed, and the following pooled rates found for: (1) 47,trisomy 13, 8.3 X 10(-5) (1/12,000); and (2) 46, (D/13 Robertsonian translocations), 4.2 X 10(-5) (1/24,000)--mutants, 1.2 X 10(-5) (1/80,000) to 1.8 X 10(-5) (1/56,000); and familial cases, 2.4 X 10(-5) (1/42,000) to 3.0 X 10(-5) (1/33,000). The rate of trisomy 13 (47, + 13) in liveborns (ignoring possible biases in studies and heterogeneity in rates) is, with 95% confidence, between 4.6 X 10(-5) (1/21,700) and 14.0 X 10(-5) (1/7,000), with the most likely figure close to 8 X 10(-5) (1/12,000). Numbers are insufficient to construct a comparably narrow confidence interval for translocation cases. The rates of 47, + 13 may be estimated in (1) spontaneous abortuses, about 0.8%--1.0% (100-fold greater than in liveborns); (2) early neonatal deaths, about 0.4% (50-fold greater than in liveborns); and (3) amniocentesis, higher than in liveborns, at least for mothers 40 years and over.

Amniocentesis↗
PubMed1979

Differences in maternal age-specific rates of Down syndrome between Jews of European origin and of North African or Asian origin.

Rates of Down syndrome in livebirths in West Jerusalem in 1964-1975 were studied in relation to the mother's continent of birth or, if she was born in Israel, to the maternal grandfather's continent of birth. In women of European origin the crude livebirth rate of Down syndrome was 1.3 per 1,000 livebirths. This crude rate and the maternal age-specific rates in this group were very close to those observed in a Swedish study and two studies of white livebirths in the United States. For West Jerusalem women of North African or Asian origin the crude rate was about 2.4 per 1,000 livebirths, and at all maternal ages except the youngest their rates were higher than for women of European origin. The summary adjusted relative risk for a Down syndrome livebirth for all those of North African or Asian origin, compared to those for women of European origin, was about 1.56. If attention is restricted to mothers born outside of Israel, the adjusted relative risk for mothers born in Europe, the Americas or English speaking countries of the British commonwealth compared to those born in North Africa or Asia was 1.97, consistent with a two-fold difference in the likelihood of a Down syndrome livebirth between thes two groups. To our knowledge this is the first report of ethnic differences in maternal age specific rates of Down syndrome that cannot be plausibly explained by differences in ascertainment.

Africa↗
PubMed1979

Maternal alcohol and tobacco consumption and their association with nausea and vomiting during pregnancy.

Nausea and vomiting during pregnancy (NVP) has been associated with favorable pregnancy outcome, though little is known about factors influencing its occurrence. In this study, information on NVP in 210 patients at a west coast health maintenance organization was obtained. Smoking and alcohol consumption before and during pregnancy were also estimated in two personal interviews during gestation. In all, 72% of the subjects had NVP in the first 4 months of pregnancy. Smokers had significantly less NVP than non-smokers (52% vs. 79%). Furthermore, NVP in smokers was negatively associated with alcohol consumption before and during pregnancy, with the stronger relation being for alcohol reported in the 6 months before pregnancy; only 46% of smokers drinking more than 1/2 fl. oz. of absolute alcohol daily in this period reported NVP, while 68% of smokers drinking less had NVP. For non-smokers, there was no relation between alcohol use in any period and NVP. The risk of NVP associated with pre-pregnancy drinking was not related to any change in alcohol consumption after conception. These results suggest an interaction between NVP, smoking, and reported alcohol consumption. The association of favorable pregnancy outcome with NVP may be in part a reflection of moderation in maternal alcohol and tobacco use.

Alcohol Drinking↗
PubMed1978

Spontaneous deaths of fetuses with chromosomal abnormalities diagnosed prenatally.

In a survey of pregnancies, in which a chromosomal abnormality was diagnosed by amniocentesis but in which the mother did not undergo an abortion, the spontaneous fetal death rate after amniocentesis for 21 fetuses with Down's syndrome was 24 per cent (or 21 per cent, considering 19 singletons only). This rate is significantly greater than the rate of 2.7 per cent among 73 fetuses with less seriously abnormal genotypes reported in this survey or of 3.3 per cent and 3.5 per cent in the Canadian and United States studies of amniocentesis. After midtrimester there is about a sixfold higher risk of spontaneous fetal death for a fetus with Down's syndrome than for one with a normal genotype. At least some (and probably a major fraction) of the discrepancy observed between maternal-age-specific rates of Down's syndrome in live births and those found after amniocentesis is due to spontaneous fetal loss. A similar inference may be drawn for trisomy 18.

Abortion, Induced↗