A multistate approach for estimating the incidence of human immunodeficiency virus by using data from a prevalent cohort study

Summary.  Cohort studies of individuals infected with the human immunodeficiency virus (HIV) provide useful information on the past pattern of HIV diagnoses, progression of the disease and use of antiretroviral therapy. We propose a new method for using individual data from an open prevalent cohort study to estimate the incidence of HIV, by jointly modelling the HIV diagnosis, the inclusion in the cohort and the progression of the disease in a Markov model framework. The estimation procedure involves the construction of a likelihood function which takes into account the probability of observing the total number of subjects who are enrolled in the cohort and the probabilities of passage through the stages of disease for each observed subject conditionally on being included in the cohort. The estimator of the HIV infection rate is defined as the function which maximizes a penalized likelihood, and the solution of this maximization problem is approximated on a basis of cubic M -splines. The method is illustrated by using cohort data from a hospital-based surveillance system of HIV infection in Aquitaine, a region of south-western France. A simulation study is performed to study the ability of the model to reconstruct the incidence of HIV from prevalent cohort data.     

The family and adults 65 years of age and over

The policy makers usually assume that the nuclear family model is almost universally favoured in our industrial and urban society. Governmental agencies are thus left with the responsibility taken over in the past by the extended family. Gerontological literature studied the family support available to the elderly. In general, research results have supported the modified extended family model. Here, the multigenerational household is defined as a living arrangement in contradiction with the nuclear family model, but able to provide support to the disabled elderly. With three random samples of non-institutionalized francophone elderly, it was possible to estimate the number of elderly people living in multigenerational households. It was observed that the elderly in such households are older and more functionally impaired than the elderly living in other kinds of households. Thus, the multigenerational household offers a potential for support neglected by policy makers. Governmental agencies should see themselves as supporters of family involvement with elderly members rather than as surrogates for the family. Les planificateurs assument que la famille nucléaire est le modèle presqu'unique adopte par les families de sociétés industrielles et urbaines. Les agences gouvernementales doivent done prendre la reléve de la famille ètendue. Les recherches en gérontologie ont pourtant démontrv que l'aide familiale est disponible aux personnes âgées. En fait, la famille contemporaine assure la plus grande part de l'aide aux personnes âgées. Le ménage multi-générationel se pose en source importante de support pour la personne âgée qui en est membre. L'observation de trois échantillons aléatoires de personnes âgées urbaines et francophones permet une estimation du nombre de personnes âgées habitant dans un ménage multigénérationel. En plus, ces personnes sont plus âgées et ont plus d'incapacités fonctionnelles que les personnes âgées seules ou vivant avec leur conjoint seulement. En conséquence, la famille nucléaire n'est pas un modèle empiriquement adéquat. Les recherches ont plutôt proposé le modèle de la famille étendue modifiée. Les agences gouvernementales devraient concevoir leur rôle en fonction du support qu'offre la famille â ses membres âgés plutôt que de se définir comme substituts familiaux.     

Debt management in a small open economy: A theoretical and an empirical study for Belgium

This article analyzes the effects of debt management and its consequence for the control of base money in a small open economy (Belgium). The study compares the effects obtained from a small theoretical model with the results of a larger empirical model.The theoretical model focuses on the financing of government by money operation, on the bond rate, and on the international reserve of the Central Bank.The empirical model is a medium-term one, including the demand and the supply sectors of the economy and permitting simultaneous analysis of real and financial variables.The effects of an endogeneous or exogenous debt management have been studied by numerical simulation of modification in the public expenditure, the world trade, and the discount rate.     

Factors influencing contraception continuation rates: The oral and the intrauterine methods

The technique of multi-sort analysis was used to compare the relative duration of use of oral and intrauterine contraception among low socio-economic groups in Baltimore City. The clinical records of over 12,000 women who had received contraception through the Baltimore public services were analyzed. The type of method a woman used was found to be the most important factor affecting her probability of continuing contraception. Her age, race, and how long she had been using the method also influenced this probability. The strictness of the criteria used for the definition of continuation rates and the fact that experience was incomplete for many intrauterine contraceptors probably in part explain the somewhat low continuation rates obtained for both methods. It is suggested that the intrinsic characteristics of each method may lead to a clinical impression favoring the oral even when statistical evidence, as presented here, favors the intrauterine method.     

No sustained effect of aerobic or resistance training on insulin sensitivity in nonobese, healthy older women

It is unclear whether long-term aerobic (AT) or resistance (RT) training can improve insulin sensitivity (IS) beyond the residual effect of the last training bout in older women (54-78 years). Therefore, a group of nonobese, healthy older women underwent 6 months of AT (n = 8) or RT (n = 10), and the authors measured IS 4 days after the last training bouts using the hyperinsulinemic-euglycemic clamp technique. Women trained 3 days/week. AT consisted of 25- to 60-min sessions of walking/jogging at 60-95% of maximal heart rate. RT consisted of three sets of nine exercises repeated 10 times at 80% of 1 repetition maximum. AT decreased fat mass, whereas both AT and RT increased fat-free mass. Neither training program, however, improved absolute or relative rates of glucose disposal. The authors therefore concluded that nonobese, healthy older women should perform AT or RT on a daily basis in order to improve IS and maintain the improvement.     

Tree-structured subgroup analysis for censored survival data: Validation of computationally inexpensive model selection criteria

The performance of computationally inexpensive model selection criteria in the context of tree-structured subgroup analysis is investigated. It is shown through simulation that no single model selection criterion exhibits a uniformly superior performance over a wide range of scenarios. Therefore, a two-stage approach for model selection is proposed and shown to perform satisfactorily. Applied example of subgroup analysis is presented. Problems associated with tree-structured subgroup analysis are discussed and practical solutions are suggested.     

On Order Statistics from Sine Distribution

We derive closed form expressions for the first two moments of order statistics from the sine distribution. For the higher moments, a recurrence relation is given. We also give a recurrence relation for the product moments. These relations will be useful for moment computations based on ordered data.     

Waiting time to exhaust lottery numbers

Questions related to lotteries are usually of interest to the public since people think there is a magic formula which will help them to win lottery draws. This note shows how to compute the expected waiting time to observe specific numbers in a sequence of lottery draws and show that surprising facts are expected to occur.