Biomedical subjects
R Skjaerven
Publications and source records attributed to R Skjaerven.
Pregnancy outcome in Norway after Chernobyl.
Pregnancy outcome has been studied in terms of legal abortions, early spontaneous abortions and total number of pregnancies (in an ad hoc study covering 6 counties) as well as various perinatal health problems (on the basis of routinely recorded data for epidemiological surveillance from the Medical Birth Registry of Norway). Apparently, no effects were observed in terms of an increased occurrence of legal abortions, while spontaneous abortions increased from 7.2% of all pregnancies during the last 12 months before the accident to 8.3% after the accident [corrected]. At the same time, the total number of pregnancies somewhat decreased. Based on monthly measurements in each municipality of external and internal (food-based) doses, dose-response associations were assessed for a number of perinatal health problems. No associations were observed.
Abdominal aortic aneurysms. Is there an association between surgical volume, surgical experience, hospital type and operative mortality? Members of the Norwegian Abdominal Aortic Aneurysm Trial.
The effects of number of operations, experience of the surgeon, and type of hospital on operative mortality have been studied in 444 patients treated for abdominal aortic aneurysms. In the elective group (n = 279) there was a significant difference in mortality between hospitals in which more than 10 such operations were done compared with those in which less than 10 were done during the study period (p = 0.05; odds ratio (OR) 2.7). In the ruptured group there was no statistically significant difference (p = 0.14; OR 1.9). In the elective group, units with vascular surgical experience had an operative mortality of 4.8% compared with 11.3% for other units (p = 0.05; OR 2.6). In the ruptured group the figures were 52.5% and 73.3% respectively (p = 0.03; OR 2.5). There was no difference in operative mortality between university, county and local hospitals. Outcome of treatment after operations for abdominal aortic aneurysm was related to number of operations carried out and experience, whereas the type of hospital seemed less important.
The prognostic role of progesterone receptor status and age in relation to axillary node status in breast cancer patients.
The prognostic role of axillary lymph node status, progesterone receptor (PgR) status, age of the patient at operation, oestrogen receptor (ER) status and tumour diameter was studied in 443 breast cancer patients treated by modified radical mastectomy. Logistic and proportional hazard regression analyses were used to estimate the prognosis from the time of operation up to 60 months. We also estimated the prognosis from 36 to 60 months for those who had survived 36 months (conditional analysis). PgR and age gave significant information in each node class, old age and PgR negativity being disadvantages. PgR status relative to node status was more important for estimating early (24 months) prognosis, while age was of more importance later (60 months). Node status and age were the only variables giving significant information in the conditional analyses. It is thus of importance to consider the time dependency of the prognostic variables when predicting survival in breast cancer patients. No effect was found for ER status or tumour diameter.
Abdominal aortic aneurysms--a study of factors influencing postoperative mortality. Norwegian Aortic Aneurysm Trial.
Factors which influenced outcome after surgery have been studied in 444 patients with abdominal aortic aneurysm included in a Norwegian multicentre study. Two-hundred and seventy-nine patients were treated electively, 51 had impending rupture and 114 had a ruptured aneurysm. In the elective group age, a large aneurysm, impaired renal function, the presence of angina pectoris and intraoperative blood loss of more than 4 units were found to significantly increase hospital mortality. In the impending rupture group excess blood loss during the operation had a negative influence on hospital death but the limited number of patients in this group restricts the value of analysis. A low systolic blood pressure and an older patient were the only 2 risk factors which had a detrimental effect on postoperative survival in the ruptured group. The formulation of a risk index for these patients was not possible although Odds ratios for the individual factors found to be of importance may give some risk estimates.
Classification of small-for-gestational age births: weight-by-gestation standards of second birth conditional on the size of the first.
Percentiles of weight-by-gestational age were constructed for first and second births, based on linked sibship-data from the Medical Birth Registry of Norway. Standards were made for weight-by-gestational age of second births conditional on whether the first birth was small-for-gestational age (SGA) or large-for-gestational age (LGA). These standards were compared with the conventional, cross-sectional standard of all second births. The relevance of the conditional standards was assessed on the basis of perinatal mortality, using logistic regression analyses. When applying cross-sectional standards of second births, more than 30% of the births following a SGA first birth were classified as SGA, compared with only 1.7% following an LGA first births. The overall risk for a perinatal loss in second births following a SGA first birth was twice that among second births following a LGA first birth. When second births were themselves categorised as SGA or non-SGA using the cross-sectional standards, the mortality among the SGA second births was such that the risk was 4 to 5 times higher following LGA first births compared with SGA first births. When conditional standards were applied to define SGA among second births, the risk relation between the subgroups (defined by classification of first birth) corresponded to the observed overall risk pattern. An unconditional SGA classification conceals important differences between clinically distinct subgroups.
Secular trends of sudden infant death syndrome and other causes of post perinatal mortality in Norwegian birth cohorts 1967-1984.
Lack of positive diagnostic criteria and increasing professional concern, probably causing increasing ascertainment, have rendered reported increases in SIDS-rates controversial. However, these problems related to cause specific mortality do not apply to the total mortality. Due to the exceptional age-at-death distribution of SIDS cases, the SIDS fraction of all deaths increases during the first year of life to reach a maximum, in the present study of 56%, from the 105th through the 125th day of life. During these days, the total mortality rate in Norway increased from 0.24 per 1,000 in 1971-72 to 0.46 in 1983-84. Thus, the observed trend, with an increase in the SIDS rate from 1.02 per 1,000 in 1971-72 to 2.34 in 1983-84, is considered true. Observed in a country where perinatal and neonatal mortality have decreased for a long period of time and still remain very low in a global perspective, the increasing SIDS rate is a matter of great concern.
Changes in frequency and indications for cesarean section in Norway 1967-1984.
We have studied the cesarean section frequencies and changing spectrum of indications in Norway during six consecutive 3-year periods from 1967 to 1984. The data set consists of 1,046,162 births notified to the Medical birth registry of Norway, of which 52,426 were specified as cesarean sections, the frequency rising from 1.9% in 1967-69 to 9.7% in 1982-84. A check for completeness of cesarean section notification was made against the birth protocols of the largest obstetrical unit in Norway. The error rate was about 3%. Information on the indication for performing cesarean section was missing in 11.4% of the cases. We grouped thirty-one specified indications under seven headings. In 1967-69 the operation was most often performed for 'maternal' reasons, followed by 'mechanical', 'abnormalities of fetal presentation' and 'acute placental' conditions. Throughout the study period, 'mechanical' (which can also be labelled 'dystocia') accounted for about one third of the indications for cesarean section, while 'maternal' (including high maternal age and pre-eclampsia) and 'acute placental' (placenta praevia and placental abruption) decreased in relative importance. 'Fetal presentation' (including twins) doubled its relative share, while increasing from 2.4 per 1000 births in 1967-69 to 24.8 per 1000 births in 1982-84. A steep rise in the group 'fetal asphyxia' corresponded to the period when the mass of electronic monitoring devices was introduced, in the early 1970s. 'Fetal asphyxia' had a higher relative share of the indications among para 0 mothers than in the total birth population.
Estrogen receptor in breast cancer; its relation to mean nuclear area, age and lymph node status.
A study of 378 patients with infiltrating breast carcinoma using linear logistic regression and ANOVA analysis demonstrated a different relation between age at operation and estrogen-receptor (ER) concentration in the lymph-node negative and the lymph-node positive groups. Tumours from patients between 51 and 70 years old had lower median ER concentration in the lymph-node negative group than in the lymph-node positive group. In the group older than 70 years, however, tumours from lymph-node negative patients had higher median ER concentrations than those from the lymph-node positive patients. Patients 50 years and younger had similar median ER concentrations in both lymph-node groups. Low mean nuclear area (MNA) of the tumour cells was associated with high frequency of tumours able to produce ER. No such association was found for age. Independent of age and lymph-node status tumours with low MNA also had high ER concentration. These findings suggest that tumours from different lymph-node/age groups may have different biological properties. The relationship between ER and nuclear size point to a key function of the nucleus, both as regards the ability to produce ER and its level of production.
[New Norwegian percentage charts for height, weight and head circumference for age groups 0-17 years].
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[Height, weight and head circumference of 0-4 year-old children. Data based on the SYSBARN registration and medical register of births].
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Perinatal mortality and mother's marital status at birth in subsequent siblings.
The effect of marital status on perinatal mortality is studied for births in Norway, 1967-1981, in terms of relative risk (RR) of unmarried vs. married mothers. The births were linked in units of sibships. At first birth, RR decreased from 1.86 in 1967-1971 to 1.32 in 1977-1981. At second birth the perinatal mortality varied greatly according to marital history with a RR of 2.03 when comparing sibships where mothers were unmarried at both pregnancies with mothers married at both pregnancies. Almost no excess risk was demonstrated for mothers that were married at second birth, but unmarried at first. These mothers appeared to have no excess risk even at the first birth in spite of being unmarried. The results suggest that marital status is still a risk factor to be considered, even in the Scandinavian countries where the marginal effect of marital status in recent years has been reported to be low. To an increasing extent, the high risk women, previously identified by marital status, are now hidden in a larger low risk group which apparently has more stable family relations, e.g. tending to be married at second birth.
Sudden infant death syndrome and recurrence in subsequent siblings.
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Sex differences in neonatal survival. Relationship to birthweight and gestational age.
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Birthweight and perinatal mortality of second births conditional on weight of the first.
A woman's successive offspring tend to have similar birthweights. We use data from the Medical Birth Registry of Norway to describe weight and perinatal mortality of second births given the weight of the mother's first birth. Mean weights among second births differ by as much as 1000 grams, depending on the weight of the first. Furthermore, the survival of the second baby at any given weight is strongly affected by its weight relative to the first baby's weight. A baby may be average size compared to the whole population, but small compared to its sibling; such a baby has the increased mortality that goes with being relatively small. For example, an infant of 3250 grams is relatively large if the mother's previous baby was 2250 grams, but relatively small if the previous birth weighed 4250 grams. In the first case, the mortality risk of the 3250-gram baby is 2.2 per thousand, while in the second case, risk for the same weight infant is 9.0, or four times higher. Implications of these observations for the more general analysis of birthweight and perinatal mortality are discussed.
Selective fertility and the distortion of perinatal mortality.
Data from the Medical Birth Registry of Norway, covering more than one million births for the period 1967-1984, were used to study the magnitude and effects of selective fertility, which is the tendency for a woman to replace a perinatal loss. Variation in fertility after the first three births is studied, controlling for perinatal outcome of previous births, maternal age, and year of birth. Even after the first birth, fertility is higher after a perinatal loss. Selective fertility is more strongly present at each successive birth order, and at each birth order it is stronger among older women. As the average number of births per woman decreases, the force of selective fertility increases; that is, its importance has increased over time. Perinatal mortality at the third and fourth birth orders is particularly distorted by the mechanism of selective fertility in studies based on cross-sectional data. Mortality at second birth is exaggerated by 1%, at third birth by 8% to 20%, and at fourth birth by 18% to 27%, with the largest effects seen in the later periods. A major portion of the increase in perinatal mortality from the second to fourth birth seen in most studies based on cross-sectional data can be explained by the mechanism of selective fertility.
Prognosis in node negative breast cancer patients: the importance of tumour diameter and mean nuclear area.
In node negative breast cancer patients, tumour size and mean nuclear area (MNA) as single variables have significant impact on prognosis. Combination of the two variables gives additional information on survival, and makes it possible to predict the outcome of the disease correctly in 70% of the patients both early (82 months) and late (154 months). MNA contributes relatively more to prediction of late prognosis than tumour diameter and vice versa for early prognosis. Thus a long follow-up is needed for node negative patients, and more so for patients with favourable prognostic criteria.
Secular changes in early neonatal mortality in Norway, 1967-1981.
Two five-year cohorts, 1967-1971 and 1977-1981, of the Medical Birth Registry of Norway, were utilized to analyze secular trends in early neonatal mortality rates, controlling simultaneously for birth weight, parity, maternal age, and sex. Improvement in the crude early neonatal mortality rate, from 6.5 to 2.9 per 1,000, was partitioned into one portion (18.4%) attributable to changes in the distribution of the birth weight or the other independent variables and another portion (81.6%) attributable to improved survival within each specific subgroup in the multivariate table. The early neonatal mortality rate was found to decrease in all subgroups, the low birth weight groups showing a significantly greater decline than the normal birth weight groups. Women with diabetes, epilepsy, or blood group antibodies were studied in separate analyses. For women with diabetes, the odds ratio of the early neonatal mortality rate between the first and the second periods was found to be three times the odds ratio for women without diabetes, and 2.9% of the total improvement of the crude early neonatal mortality rate was attributable to an improved survival in these infants.