Estimating sibling recurrence risk in population sample surveys.

BACKGROUND/AIMS: Sibling recurrence risk (SRR) is a measure of familial aggregation of a disease and is often used in family-based studies in genetic epidemiology to indicate the existence of possible genes conferring susceptibility of disease. Estimating SRR requires information about the disease status of sibships of families with two or more siblings where at least one is affected. Since family-based studies are not usually random samples, estimates of SRR derived from these studies may be biased. Network sampling used in survey research offers a way to ascertain the disease status of sibships from interviewed individuals in household survey samples, in order to obtain (approximately) unbiased estimators of SRR and its related SRR ratio (SRR divided by the prevalence of disease). METHODS: Two methods of ascertaining sibships of affected families are considered: in one method the siblings' affected status is reported by an individual, regardless of the individual's affected status, and in the other method only affected individuals can report their siblings' affected status. Network estimators of SRR and SRR ratio and estimators of their standard errors are provided. RESULTS: Reported diabetes for siblings from the 1976 National Health Interview is used to illustrate the estimation methods. The SRR ratio for diabetes among living siblings was 5.79% [relative standard error (RSE) = 5.12%], and for living or deceased siblings, it was 7.66% (RSE = 3.76%). CONCLUSIONS: Network sampling estimators can provide population estimates of SRR and SRR ratio for diseases such as diabetes.

Linked surveys of health services utilization.

The linked population/establishment survey (LS) of health services utilization is a two-phase sample survey that links the sample designs of the population sample survey (PS) and the health-care provider establishment sample survey (ES) of health services utilization. In Phase I, household respondents in the PS identify their health-care providers during a specified calendar period. In Phase II, health-care providers identified in Phase I report the variables of interest for all or a sample of their transactions with all households during the same calendar period. The LS has been proposed as a potential design alternative to the PS whenever the health-care transactions of interest are hard to find or enumerate in household surveys and as a potential design alternative to the ES whenever it is infeasible or expensive to construct or maintain complete sampling provider frames that list all health-care providers with good measures of provider size. Suppose that the non-sampling errors are ignorable, how do the LS, PS and ES sampling errors compare? This paper addresses that question by summarizing and extending recent research findings that compare expressions of the sampling variance of (1) the LS and PS of equivalent household sample size and (2) the LS and the ES of equivalent expected health-care provider and transaction sample sizes. The paper identifies the parameters contributing to the precision differences and assesses the conditions that favour the LS or one or the other surveys. Published in 2007 by John Wiley & Sons, Ltd.

The retiring ophthalmologist - reflections in amber

After all the years of hard work, after all the years of planning and positioning, there comes a time when most ophthalmologists will have to adjust to the inevitable life changes that he or she will face. The preparation for this change will make the difference between contentment and frustration for many. The focus of the eye surgeon changes from decade to decade almost imperceptyibly and, while many react to the changes as they happen, others attempt to manage the change in focus. Knowing what to expect from oneself and understanding how to prepare for the diminishing years, will lead to self realization and self actualization, and for the ophthalmologist on the down slope of his years this knowledge is all important.(AU)

13-cis-retinoic acid affects oxidation and DNA damage in oxidative-positive SLE lymphocytes but may not be useful for therapy.

13-cis-Retinoic acid (13-CRA), a water-soluble vitamin A analog and 5'-lipoxygenase inhibitor, was tested in vitro for effects on excess oxidative metabolism and DNA damage in mitogen-stimulated lymphocytes from patients with systemic lupus erythematosus (SLE), because other 5'-lipoxygenase enzyme inhibitors were shown to lower the excess oxidative metabolism in SLE cells. Excess chemiluminescence (CL) was abolished within minutes after the addition of 1 x 10(-6) M 13-CRA in five of five CL-positive mitogen-stimulated SLE lymphocytes, and was lowered in five of eight samples after 48 to 72 h culture. Similarly, low concentrations of 13-CRA for 48-72 h largely prevented the S1 nuclease-sensitive DNA changes/DNA damage observed in CL-positive lupus lymphocytes in vitro. However, 13-CRA did not affect DNA damage in four of four CL-negative lymphocyte samples. 13-CRA, like other retinoic acid compounds, was known to stimulate B-cell activities in vivo and in vitro but effects on dividing lupus T cells had not been studied. 13-CRA further inhibited the diminished PHA-stimulated lupus T-cell growth in tissue culture at a concentration of 9 x 10(-6) M in three of five lupus lymphocyte samples. 13-CRA has positive and negative effects on multiple aspects of the immune system and it is not clear whether 13-CRA will have positive or adverse clinical effects on SLE patients. Close attention to vitamin A and vitamin "supplements" in patients with SLE may answer this question.

Correlation of perinatal brain growth with age, body size, sex, and race.

This study compares the weight of the human brain to gestational age and body dimensions. A new formula for calculating the rate of growth is proposed. It consists of a second order polynomial function: Y = A0 + A1X + A2X2, in which Y is brain weight, body weight, height, or body surface area; X is gestational age in weeks and A0, A1, and A2 are statistically estimated coefficients. In utero, the growth rate is most rapid for body weight, followed in decreasing order by brain weight, body surface area, and height. Brain growth is the same for both sexes in black and white races; it accelerates between the 20th and 45th weeks of gestation. The size of the newborn infant brain is directly related to gestational age and body size and is not determined by sex or race.

The weight of the infratentorial portion of the adult brain and analysis of the infratentorial/whole brain weight ratio.

A direct relationship exists between the weights of the infratentorial portion (ITP) of the brain and the whole brain. With aging, the weight of the ITP decreases, but the decrease begins later and is smaller than for the forebrain. With whole brain weights, there are significant differences in the weight of the ITP between sexes and between the races. The weight of the ITP increases slightly with increase in body weight. The infratentorial/whole brain ratio is stable during adult life and does not vary with body dimensions. The ratio increases after age 80 because of the accelerated loss of mass of the forebrain. The ratio is the same for both races, but it is significantly higher for the females than for the males. The difference is best accounted for by an arrest in the growth of the forebrain in the female during adolescence.

Newborn brain weight in relation to maturity, sex, and race.

Fresh brain weight, gestational age, body weight, sex, and race were collected from autopsy records of 782 newborns over a 10-year period. The brain weight of the mature newborn does not differ between males and females or between white and black infants. For the premature, however, brain weight is heavier in white males than in black males and in white females than in black females. These differences are similar to those found for adults in our previous studies, and they correspond to differences in gestational age and body weight in the subgroups. The differences in brain weight between races are best explained on the basis of environmental factors.

Analysis of brain weight. I. Adult brain weight in relation to sex, race, and age.

The weights of fresh brains obtained at consecutive autopsies over a period of five years were reviewed. Brains with lesions, such as large tumor, hemorrhage, infarct, or edema, were excluded. Analysis of the brain weight of 1,261 subjects, aged 25 to 80 years, show that the mean brain weight decreases in order from white men to black men to white women to black women. These differences are statistically significant and become apparent at age 6 years. The rate of decrease for the brain weight after age 25 years is highest for white men, followed by black women, white women, and black men, and, except that between white men and white women, the differences are statistically insignificant. Contrary to earlier reports, the mass decreases rapidly after age 80 years. In evaluating an individual brain weight, it is important to compare it with the norm for each subgroup of a given age.

Analysis of brain weight. II. Adult brain weight in relation to body height, weight, and surface area.

Analysis of 1,261 adult subjects, ages 25 to 80 years, showed that there is a positive relationship between the brain weight and the body dimensions. The brain weight, however, increases at a slower rate than the body dimensions. There is indication that only a small portion of the brain varies with variation in the body dimensions. Among parameters, the brain weight correlates best with the body surface area, followed by the body height and body weight. The brain weight is related to the body weight partly because it increases with increasing height. When adjusted to body dimensions, the brain weight is greater for white men than for black men and for white women than for black men. Our study also shows that the loss of brain mass proceeds at a slightly faster rate than loss of body mass.

Hemodynamic alterations during septal or right ventricular ischemia in dogs.

This study indicates that in dogs, ischemic injury to just the ventricular septum has little effect on left ventricular function. The data demonstrate that ischemic injury to either the right ventricular free wall or the ventricular septum alters right ventricular function and/or compliance, suggesting that both regions play a role in maintaining right ventricular performance. That septal contraction supports right ventricular function may explain why in earlier studies, right ventricular pressure development and output were little affected by severe injury to the free wall.