Search PubMed⌕ Search

Biomedical subjects

Odd O Aalen

Publications and source records attributed to Odd O Aalen.

5 recordsLinked to original sources
PubMed2004

Analysis of testicular cancer data using a frailty model with familial dependence.

Previously published papers have indicated a fairly strong familial dependence intesticular cancer patients. This is particularly evident in brothers. We have applied a frailty model with familial dependence to family data on brothers of testicular cancer patients from the Norwegian Radium Hospital. The model is a two-level frailty, with variation in susceptibility at both the family and the individual level. Specifically, the frailty variable is assumed to be compound Poisson distributed to allow individuals to be non-susceptible. The underlying Poisson parameter is gamma distributed to model how testicular cancer is distributed among families. This is an extension of a previous compound Poisson frailty model developed for individual testicular cancer data, and an alternative to traditional modelling of survival time family data. The likelihood construction and ascertainment problems are looked at in detail. To avoid ascertainment bias, the likelihood is based on the probability of observing the disease status for each brother in a family, given that at least one brother is ascertained. The estimated relative risk for brothers is 7.4. This paper expands on a previous analysis of the data by using a frailty model, which makes it possible to examine how the cancer is distributed among families. The estimated gamma-shaped parameter is 0.151 (95 per cent confidence interval 0.078-0.294), and this indicates that in order to obtain the high relative risks observed for brothers of testicular cancer patients, the distribution of susceptibility has to be strongly skewed among the families. The vast majority of families have a very low risk and a small proportion have a high risk. In addition, a quantity similar to the relative risk is derived to show that the susceptibility is skewly distributed also if the Poisson parameter is Bernoulli or stable distributed. This indicates that the results are valid also if other distributions are used to model familial dependence in the compound Poisson frailty model.

Genetic Predisposition to Disease↗
PubMed2004

Frailty modelling of testicular cancer incidence using Scandinavian data.

The incidence of testicular cancer is highest among young men, and then decreases sharply with age. This points towards a frailty effect, where some men have a much greater risk of testicular cancer than the majority of the male population. Those with the highest risk get cancer, drain the group of individuals at risk, and leave a healthy male population which has approximately zero risk of testicular cancer. This leads to the observed decrease in incidence. We discuss a frailty model, where the frailty is compound-Poisson-distributed. This allows for a non-susceptible group (of zero frailty). The model is successfully applied to incidence data from the Danish and Norwegian registries. It is indicated that there was a decrease in incidence for males born during World War II in both countries. Bootstrap analysis is used to find the degree of variation in the estimates. In the Armitage-Doll multistage model, the estimated number of transitions needed for a cell to become malignant is close to 3 for non-seminomas and 4 for seminomas in both the Danish and Norwegian data. This paper demonstrates that a model including a frailty effect fits the incidence data well and gives interesting results and interpretations, although this is no proof of the effect's truth.

Adolescent↗
PubMed2003

Legal access to needles and syringes/needle exchange programmes versus HIV counselling and testing to prevent transmission of HIV among intravenous drug users: a comparative study of Denmark, Norway and Sweden.

BACKGROUND: Countries have adopted different strategies to prevent the transmission of HIV among intravenous drug users. Legal access to needles and syringes/needle exchange programmes as part of such a strategy has been heavily debated. HIV counselling and testing has also been part of prevention strategies. The objective of this study was to discuss the effectiveness of legal access to needles and syringes/ needle exchange programmes versus HIV counselling and testing among intravenous drug users (IDUs) as part of HIV prevention strategies. METHODS: Differences in HIV prevention strategies in Denmark, Norway and Sweden among IDUs are described. Outcome variables of effectiveness were HIV incidence rates over time. These were estimated by back calculation methods from 1980 through 1996, using data from the national HIV and AIDS registers. RESULTS: A comparison of HIV prevention strategies in Denmark, Norway and Sweden suggests that a high level of HIV counselling and testing might be more effective than legal access to needles and syringes/needle exchange programmes. Sweden and Norway, with higher levels of HIV counselling and testing, have had significantly lower incidence rates of HIV among IDUs than Denmark where there was legal access to needles and syringes and a lower level of HIV counselling and testing. In Sweden there was no legal access to drug injection equipment. CONCLUSION: Promotion and accessibility of HIV counselling and testing among intravenous drug users should be considered in countries where such a strategy is not adopted or has low priority.

AIDS Serodiagnosis↗
PubMed2003

Resuscitation of newborn infants with 21% or 100% oxygen: follow-up at 18 to 24 months.

OBJECTIVE: To follow-up children who had been resuscitated at birth with either 21% or 100% oxygen (O2). METHODS: A multicenter study with 10 participating centers recruited 609 infants to the Resair 2 study where resuscitation was performed with either 21% or 100% O2. A follow-up between ages 18 and 24 months was performed. However, during follow-up registration, it was found that 18 infants had been enrolled twice in the original Resair 2 study with different registration numbers, leaving 591 enrolled in the Resair 2 study and 410 enrolled in the 7 centers participating in the follow-up. Of these 410 infants, 79 died (76 in the neonatal and 3 in the postneonatal period). Furthermore, for 8 infants informed consent was not obtained, leaving 323 eligible for follow-up. Of these, 213 infants (66%) were followed-up: 91 (62%) had been resuscitated with 21% O2, and 122 (69%) with 100% O2. At a median age of 22 and 20 months (not significant) in the 21% and 100% groups, respectively, a simple questionnaire was filled out and neurologic assessment was performed in addition to measuring anthropometric data. RESULTS: There were no significant differences in weight, height, or head circumference between the 2 groups. Cerebral palsy developed in 10% and 7%, respectively, in the 2 groups (not significant). In total, 11 cases (12%) in the 21% versus 11 cases (9%) in the 100% O(2) group (odds ratio: 1.39, 95% confidence interval: 0.57-3.36) developed cerebral palsy and/or mental or other delay. Furthermore, it was concluded that 14 (15%) in the 21% group and 12 (10%) in the 100% group were not normal (odds ratio: 1.67, 95% confidence interval: 0.73-3.80). CONCLUSIONS: There were no significant differences in somatic growth or neurologic handicap at an age of 18 to 24 months in infants resuscitated with either 21% or 100% O2 at birth. Based on these data, resuscitation with ambient air seems to be safe, at least in most cases. More studies are needed to settle this issue.

Birth Weight↗