The Jerusalem Perinatal Study cohort, 1964-2005: methods and a review of the main results

Very high birth weight of offspring is associated with an increased risk of leukemia in their mothers: results of a population-based cohort study

Although the association between birth weight and childhood leukemia is well described, the relation between a child's birth weight and parental risk of leukemia is unknown. We linked data from the Jerusalem Perinatal Study to the Israel Cancer Registry to ascertain the incidence of leukemia in mothers and fathers in relation to their offspring's birth weight. Birth weight >or=4500 g in any of the offspring was associated with a >3-fold risk of leukemia in mothers, but not fathers. Potential mechanisms include shared exposures of high birth weight infants and their mothers, possibly to radiation or growth factors, or genetic pathways leading to both high birth weight and leukemia.

Twin pregnancy and the risk of schizophrenia

BACKGROUND

Twins are exposed to intrauterine environments that differ significantly from those of singletons. These diverse environments might alter the risk for schizophrenia in twins and make it difficult to generalize from findings in twins when studying the risk of schizophrenia in the general population. Previous studies report contradictory findings on the risk for schizophrenia in twins.

METHODS

We studied the incidence of schizophrenia spectrum disorders, ascertained from Israel's National Psychiatric Registry, in a cohort of 2124 twins and 87,955 singletons. These offspring were followed from their birth in 1964-76 in the Jerusalem Perinatal study. Cox proportional hazards methods were used to compare outcomes over 28-41 years, adjusting for ages of parents.

RESULTS

Twins showed a relative risk [RR] of .84 relative to singletons, with a 95% confidence interval [CI] of (.51-1.4). RRs and CIs for males and females were .68 [.34-1.4] and 1.1 [.55-2.2] respectively. Twins in male-male, female-female or opposite-sex sets showed no significant variation in RRs; furthermore, first- or second-born twins did not differ significantly from each other. Siblings of twins had the same risk of schizophrenia as siblings of singletons.

CONCLUSION

Twins have the same risk for schizophrenia as the general population.

Paternal age and twinning in the Jerusalem Perinatal Study

OBJECTIVE

To investigate whether incidence of twin deliveries is related to father's age, independently of mother's age, and whether it differs for same-sex or opposite-sex twin sets.

STUDY DESIGN

In a program of research on effects of paternal age, this study used data from a prospective cohort of 92,408 offspring born in Jerusalem from 1964 to 1976. Of the 91,253 deliveries in the Jerusalem Perinatal Study, 1115 were twin deliveries. The data were analyzed with General Estimate Equations to inform unconditional logistic regression.

RESULTS

After controlling for maternal age, odds ratios (ORs) and 95% confidence intervals (95% CI) associated with father's ages 25-34 and 35+ were 1.3 (1.1, 1.7) and 1.5 (1.2, 2.1) respectively, compared with fathers <25 years old. The effect of maternal age was partly explained by paternal age. The ORs for opposite-sex twin sets and male-male twin sets increased slightly with paternal age, while the OR for same-sex and female-female twin decreased.

CONCLUSION

Studies of twins are used to estimate effects of genes and environment in a variety of diseases. Our findings highlight the need to consider paternal as well as maternal age when analyzing data on twins to explore etiology of diseases.

Acute maternal stress in pregnancy and schizophrenia in offspring: a cohort prospective study

Schizophrenia has been linked with intrauterine exposure to maternal stress due to bereavement, famine and major disasters. Recent evidence suggests that human vulnerability may be greatest in the first trimester of gestation and rodent experiments suggest sex specificity. We aimed to describe the consequence of an acute maternal stress, through a follow-up of offspring whose mothers were pregnant during the Arab-Israeli war of 1967. A priori, we focused on gestational month and offspring's sex.

METHOD

In a pilot study linking birth records to Israel's Psychiatric Registry, we analyzed data from a cohort of 88,829 born in Jerusalem in 1964-76. Proportional hazards models were used to estimate the relative risk (RR) of schizophrenia, according to month of birth, gender and other variables, while controlling for father's age and other potential confounders. Other causes of hospitalized psychiatric morbidity (grouped together) were analyzed for comparison.

RESULTS

There was a raised incidence of schizophrenia for those who were in the second month of fetal life in June 1967 (RR = 2.3, 1.1-4.7), seen more in females (4.3, 1.7-10.7) than in males (1.2, 0.4-3.8). Results were not explained by secular or seasonal variations, altered birth weight or gestational age. For other conditions, RRs were increased in offspring who had been in the third month of fetal life in June 1967 (2.5, 1.2-5.2), also seen more in females (3.6, 1.3-9.7) than males (1.8, 0.6-5.2).

CONCLUSION

These findings add to a growing literature, in experimental animals and humans, attributing long term consequences for offspring of maternal gestational stress. They suggest both a sex-specificity and a relatively short gestational time-window for gestational effects on vulnerability to schizophrenia.

Consanguinity and birth defects in the jerusalem perinatal study cohort

BACKGROUND

While parental consanguinity is known to increase the risk of birth defects in offspring, it is hard to quantify this risk in populations where consanguinity is prevalent.

METHODS

To support ongoing studies of cancer and of psychiatric disease, we studied relationships of consanguinity to 1,053 major birth defects in 29,815 offspring, born in 1964-1976. To adjust for confounding variables (geographic origin, social class and hospital), we constructed logistic regression models, using GEE to take into account correlations between sibs. Odds ratios (ORs) and 95% confidence limits were estimated in comparison to a reference group of offspring with grandfathers born in different countries.

RESULTS

With 10.1% of offspring having consanguineous parents, the adjusted OR for major birth defect was 1.41 (1.12-1.74). Offspring of marriages between uncles-nieces, first cousins and more distant relatives showed adjusted ORs of 2.36 (0.98-5.68), 1.59 (1.22-2.07) and 1.20 (0.89-1.59) respectively. For descendents of grandfathers born in the same country, but not known to be related, the OR was 1.05 (0.91-1.21); these showed increased risk associated with ancestries in Western Asia (1.27, 1.04-1.55, p < 0.02) or Europe (1.13, 0.79-1.80).

CONCLUSIONS

A strong association of consanguinity with poverty and low education points to the need to avoid exposure to environmental hazards in these families.

Prepregnancy body mass index, hypertensive disorders of pregnancy, and long-term maternal mortality

OBJECTIVE

Recent studies have shown increased maternal mortality rates after hypertensive disorders of pregnancy (HDP), but the reasons for this increase remain unclear. This study examines the relationship between elevated prepregnancy body mass index (BMI), HDP, and postpregnancy mortality.

STUDY DESIGN

Data came from a 1975-1976 subset (n = 13,722 women) of a population-based cohort. Multiple logistic regression was used to examine the risk of HDP by BMI; age-adjusted Cox proportional hazards models were used to examine survival rates.

RESULTS

Overweight (BMI, 25-29.9 kg/m2) and obesity (BMI, > or = 30 kg/m2) were associated with increased HDP (odds ratio [OR], 2.82; 95% confidence interval [CI], 2.40-3.31 and OR, 5.51; 95% CI, 4.15-7.31]) and decreased survival (hazard ratio [HR], 1.42; 95% CI, 1.10-1.83 and HR, 2.43; 95% CI, 1.61-3.68), compared with normal weight (BMI, 18.5-24.9 kg/m2). HDP was significantly associated with increased mortality rates for women who survived > 15 years (HR, 1.94; 95% CI, 1.42-2.67]; HR adjusted for BMI, 1.65; 95% CI, 1.19-2.79]). A greater increase in risk of death after HDP was seen in the overweight women (HR, 1.86; 95% CI, 1.07-3.20) and obese women (HR, 2.90; 95% CI, 1.28-6.58), compared with normal weight women (HR, 1.26; 95% CI, 0.74-2.14).

CONCLUSION

Elevated prepregnancy BMI is associated with increased risk of HDP, which are in turn is associated with increased long-term maternal mortality rates. This association between HDP and mortality rates increases with elevated prepregnancy BMI.

Gestational diabetes as a risk factor for pancreatic cancer: a prospective cohort study

BACKGROUND

Diabetes is known to be associated with cancer of the pancreas, though there is some debate as to whether it is a cause or a consequence of the disease. We investigated the incidence of pancreatic cancer in a cohort of 37926 Israeli women followed for 28-40 years for whom information on diabetes had been collected at the time they gave birth, in 1964-1976, in Jerusalem. There were 54 cases of pancreatic cancer ascertained from the Israel Cancer Registry during follow-up.

METHODS

We used Cox proportional hazards models to adjust for age at baseline and explore effects of other risk factors, including ethnic groups, preeclampsia, birth order and birth weight of offspring.

RESULTS

We observed no cases of pancreatic cancer in the women with insulin dependent diabetes; however, there were five cases in the women with gestational diabetes. The interval between the record of diabetes in pregnancy and the diagnosis of pancreatic cancer ranged from 14-35 years. Women with a history of gestational diabetes showed a relative risk of pancreatic cancer of 7.1 (95% confidence interval, 2.8-18.0).

CONCLUSION

We conclude that gestational diabetes is strongly related to the risk of cancer of the pancreas in women in this population, and that gestational diabetes can precede cancer diagnosis by many years.

Gestational diabetes and the risk of breast cancer among women in the Jerusalem Perinatal Study

Gestational diabetes is becoming increasingly common; it is important to determine how it relates to future risk of disease. We investigated the relation of gestational diabetes to breast cancer in 37,926 women who had one or more live births in 1964-1976 for whom information had been collected on complications of pregnancy. In this cohort there were 1,626 cases of breast cancer reported to the Israel Cancer Registry before January 1, 2005 and 410 cases of gestational diabetes recorded from birth records. There were 29 cases of breast cancer among women diagnosed with gestational diabetes. Using Cox proportional hazards models to control for age and birth order at the first observed birth and other characteristics, we found that the incidence of breast cancer was increased among women diagnosed with gestational diabetes (relative rate = 1.5, 95% confidence interval 1.0-2.1). This effect was seen only among women 50 years and older (relative rate 1.7, 95% confidence interval 1.1-2.5) but not among women <50 (relative rate = 1.0, 95% confidence interval 0.5-2.1). The findings suggest that gestational diabetes may be an important early marker of breast cancer risk among post-menopausal women, but these results need to be confirmed in future studies.

Prostate cancer in fathers with fewer male offspring: the Jerusalem Perinatal Study cohort

Recent studies have suggested the involvement of loci on the Y chromosome in prostate cancer. We studied the relative risk (RR) of prostate cancer in relation to sex ratio of offspring in a cohort of 38,934 Israeli men who were followed from the birth of their offspring (in 1964 through 1976) until 2005. Cox models were used to adjust for changes in incidence over time, age, the man's year of birth, and social and ethnic variables. A total of 712 men were diagnosed with prostate cancer. Compared with men who had at least one son, men with only daughters had an increased risk of prostate cancer (adjusted RR = 1.40, 95% confidence interval [CI] = 1.20 to 1.64, P<.0001). In men with one, two, or three or more offspring, the relative risks associated with absence of sons were 1.25 (95% CI = 1.00 to 1.56), 1.41 (95% CI = 1.04 to 1.91), and 1.60 (95% CI = 1.05 to 2.43), respectively. Men with no daughters showed no statistically significantly altered risk, compared with men who had offspring of both sexes. The relative risk of prostate cancer decreased as the number of sons increased (P(trend)<.0001) but did not change with the number of daughters. These findings suggest that a Y chromosome locus may be involved in prostate cancer risk in this population.

Tetrachloroethylene exposure and risk of schizophrenia: offspring of dry cleaners in a population birth cohort, preliminary findings

Tetrachloroethylene is a solvent used in dry cleaning with reported neurotoxic effects. Using proportional hazard methods, we examined the relationship between parental occupation as a dry cleaner and risk for schizophrenia in a prospective population-based cohort of 88,829 offspring born in Jerusalem from 1964 through 1976, followed from birth to age 21-33 years. Of 144 offspring whose parents were dry cleaners, 4 developed schizophrenia. We observed an increased incidence of schizophrenia in offspring of parents who were dry cleaners (RR=3.4, 95% CI, 1.3-9.2, p=0.01). Tetrachloroethylene exposure warrants further investigation as a risk factor for schizophrenia.