Does it make sense to do repeated surveys?--the Lundby Study, 1947-1997.

OBJECTIVE: To describe the Lundby Study and the difficulties in doing repeated surveys. METHOD: Best-estimate consensus diagnoses have been used since 1957 together with DSM-IV and ICD-10 in 1997. RESULTS: The Lundby population consisting of 3563 probands was investigated in 1947, 1957 and 1972. Sufficient information was available for 98-99%. In 1997-2000 a fourth field investigation was carried out. Attrition rate for the interviews was 13% (238/1797). About 36% (1030/2827) had died between 1972 and 1997, but data from registers, case notes and key-informants for the period 1972 and 1997 completed the information for 94% (2659/2827). The population has followed the same pattern of development as many rural populations in Sweden since the 1940s. Multiple sources of information are preferable in longitudinal studies in order to tackle the problem of changing diagnostic systems. CONCLUSION: Low attrition rates over 50 years and reasonable diagnostic uniformity make comparisons over time justifiable.

Is smoking in pregnancy interrelated between generations?

In order to compare pregnancy smoking habits in two generations, data on first generation deliveries in 1964-67 were obtained from prospective questionnaires. By record linkage with the Swedish Medical Birth Registry, data on daughters giving second generation births (n = 1659) were obtained, including prospective smoking information. The catchment area was that of Helsingborg County Hospital (population 145,000). Second generation births until December 31, 1993 were identified in all of Sweden. The odds ratio of maternal smoking in the first generation for pregnancy smoking among the daughters was significantly increased and approximately doubled. Adjustment for confounders was made using the Mantel-Haenszel method. Similar odds ratios remained after stratification either for a social environment index of the first generation or the educational level of the second generation. Thus, our data suggest a biological association between pregnancy smoking habits over generations. Research on causative mechanisms could help design more efficient intervention programs. In a separate analysis of two parturient cohorts in Helsingborg 30 y apart, we found that the prevalence of maternal smoking had decreased comparatively more among younger than older women.

Smoking in pregnancy as a risk factor for long-term mortality in the offspring.

This study addresses the question of whether maternal smoking is related to postneonatal mortality and which are the contributing causes of death. Mortality of births in Sweden between 1 January 1983 and 31 December 1989 (n = 714,389) registered in the Medical Birth Registry was followed until 31 December 1990. The registry carries information on maternal smoking habits in early pregnancy. The Mantel-Haenszel procedure was used to control for confounding effects of maternal age, parity and year of birth: relative risks (95% confidence interval) associated with smoking were: 1.24 (1.17-1.31) for fetal death, 1.08 (1.01-1.16) for early neonatal death, 1.22 (1.08-1.39) for late neonatal death, 1.31 (1.23-1.41) for postneonatal mortality during the first year, and for the period between 1 and 8 years of age it was 1.19 (1.06-1.32). When birthweight was controlled for, the increased relative risk for postneonatal mortality during the first year disappeared. Mortality between 1 and 8 years still showed an elevated risk of 1.43 (1.00-2.06). In order to control for confounding by social factors, 1986 births were linked to data from the 1985 Swedish census. The measure used was the socio-economic index (SEI), which reflects the parental education level. When maternal, paternal or family SEI was controlled for, late neonatal death was not significantly related to maternal smoking, but postneonatal death still showed a significantly increased relative risk of about 1.35. Four causes of death based on International Classification of Diseases (ICD) 8 and 9 were significantly related to maternal smoking: sudden infant death syndrome, injuries and poisoning, perinatal causes and infections.