P–724 The association between use of assisted reproductive techniques and childhood asthma: a Swedish nationwide register-based cohort study

Study question

Are the previously reported greater risks of childhood asthma in children conceived by assisted reproductive techniques due to the intervention or unmeasured parental confounding?

Summary answer

After accounting for both measured and unmeasured parental factors we found no indication that the use of assisted reproductive techniques increases children’s risk of asthma.

What is known already

Several earlier studies have reported a higher risk of childhood asthma among children conceived by ART. However, only one previous study has attempted a sibling comparison to account for infertility as well as parental background factors, and their findings need to be replicated. Little is thus known on what underlies the higher risk of childhood asthma.

Study design, size, duration

In this nationwide register-based cohort, we identified all 1,671,532 live births between 1997 and 2013 in the Swedish Medical Birth Register (MBR) and followed them to the end of 2018.

Participants/materials, setting, methods

Infertility and ART use were ascertained from IVF clinic reporting, clinical diagnosis, and maternal self-report during the first antenatal visit. Childhood asthma was identified from diagnosis in hospitalization and outpatient specialist care records, and dispensations of asthma medication. Cox proportional hazard regression was used to estimate the association of ART and asthma in the population, in children of couples with known infertility, and in a sample of siblings conceived with and without ART (differentially exposed).

Main results and the role of chance

Of the 1,671,532 live births in the cohort, 11.7% were born to couples with known infertility, and 3.5% were conceived with ART. Compared with all other children, children conceived by ART had a small, elevated risk of asthma (adjusted hazard ratio (aHR)=1.14, 95% Confidence interval (CI) 1.11 to 1.16). When the comparison was restricted to children of couples with known infertility the difference in risk was even smaller (aHR=1.07, 95% CI 1.05 to 1.10), and in the comparison of siblings conceived with and without ART no difference in risk was seen (aHR=0.98, 95% CI 0.86 to 1.13). Among children conceived with ART, those in which intra-cytoplasmic sperm injection (ICSI) had been used had a slightly lower risk of asthma (aHR=0.93, 95% CI 0.90 to 0.97), and no difference in risk was seen between use of fresh and frozen-thawed embryo transfer.

Limitations, reasons for caution

Sibling comparison is sensitive to potential misclassification, unmeasured confounding and carryover effects, so should be interpreted with this in mind. Differences in treatment implementation across time and settings could affect the ability to extrapolate the conclusions to another clinical context (where e.g., single-embryo transfer policy is not implemented).

Wider implications of the findings: This study found a modestly elevated risk of asthma in children conceived with ART to be largely explained by confounding from parental background factors. There were further no indications of adverse influence from increasingly utilized ART procedures such as ICSI or embryo-freezing, with respect to asthma in childhood.

Trial registration number

Not applicable

Exposure to acid-suppressing drugs during pregnancy and the risk of asthma in childhood: an observational cohort study

BACKGROUND

Some research has suggested a potential link between prenatal exposure to proton pump inhibitors (PPIs) or H2 -receptor antagonists (H2 RAs) and the development of childhood asthma.

AIM

To quantify the relative risk of asthma in children who experienced pre-natal exposure to PPIs and/or H2 RAs, adjusting for potential confounders.

METHODS

In this observational cohort study (NCT01787435), women aged 18-45 years with completed pregnancies between January 1996 and December 2010 were identified from The Health Improvement Network in the United Kingdom, and were linked to infants. Hazard ratios (HRs) were estimated using Cox proportional hazard models.

RESULTS

Our analysis identified 2371 prenatally exposed and 7745 unexposed infants. The incidence of asthma (per 1000 person-years) was 19.52 in the unexposed cohort, 23.88 in the PPI cohort and 32.16 in the H2 RA cohort. After adjusting for maternal healthcare utilisation during the year before pregnancy, the HR for asthma in infants whose mothers received prescriptions at any time during pregnancy was 1.12 (95% confidence interval: 0.88-1.44) for PPIs and 1.43 (1.20-1.70) for H2 RAs, when compared with unexposed infants. With further adjustment for maternal comorbidities and other medications, the HR for asthma was 1.03 (0.76-1.40) for PPIs and 1.32 (1.05-1.64) for H2 RAs.

CONCLUSIONS

Our analysis showed no association between prenatal exposure to PPIs and asthma in childhood after adjusting for confounders. The association found for H2 RAs may be explained largely by underlying environmental or genetic factors, as suggested by reductions in hazard ratio estimates following adjustment for maternal comorbidities.

Comparative safety of antiepileptic drugs during pregnancy

OBJECTIVE

To assess the safety of the newer antiepileptic drugs (AEDs) during pregnancy.

METHODS

The study population was pregnant women who enrolled in the North American AED Pregnancy Registry between 1997 and 2011. Data on AED use and maternal characteristics were collected through phone interviews at enrollment, at 7 months' gestation, and postpartum. Malformations were confirmed by medical records. The risk of major malformations was calculated among infants exposed to specific AEDs in monotherapy during the first trimester of pregnancy and among an unexposed group. Risk ratios (RRs) and 95% confidence intervals (CIs) were estimated with logistic regression.

RESULTS

The risk of major malformations was 9.3% (30 of 323) for valproate, 5.5% (11 of 199) for phenobarbital, 4.2% (15 of 359) for topiramate, 3.0% (31 of 1.033) for carbamazepine, 2.9% (12 of 416) for phenytoin, 2.4% (11 of 450) for levetiracetam, and 2.0% (31 of 1,562) for lamotrigine. Compared with lamotrigine, the RR was 5.1 (95% CI 3.0-8.5) for valproate, 2.9 (1.4-5.8) for phenobarbital, and 2.2 (1.2-4.0) for topiramate. The proportion of women with epilepsy who had seizures during pregnancy ranged from 23% for valproate to 31% for lamotrigine. Valproate was associated with a higher risk of neural tube defects, hypospadias, cardiac defects, and oral clefts and phenobarbital with a higher risk of cardiac defects and oral clefts; 5 infants exposed to topiramate (1.4%) had a cleft lip.

CONCLUSIONS

AEDs such as valproate and phenobarbital were associated with a higher risk of major malformations than newer AEDs such as lamotrigine and levetiracetam. Topiramate was associated with an increased risk of cleft lip compared with that of a reference population.

Diabetes therapy and cancer risk: causal effects and other plausible explanations

Four reports in Diabetologia presented data on the association between hypoglycaemic agents and the risk of cancer. One study showed a higher risk of cancer overall in subjects with diabetes receiving insulin or sulfonylureas than in those on metformin. In another study, the risk of cancer overall increased with dose for any type of insulin and, among high doses, insulin glargine (A21Gly,B31Arg,B32Arg human insulin)-only users had a higher risk than subjects on human insulin. In two studies, users of insulin glargine alone had a higher risk of breast cancer than those on other insulins, a third study found no association. Whether these associations are causal or at least partially explained by chance or biases such as confounding, reverse causation, selection or detection biases is arguable. Current epidemiological evidence is insufficient to confirm a carcinogenic effect of specific insulins on specific cancers. However, the potential dose effect of insulin overall, and insulin glargine in particular, on colon and breast cancer deserves further attention.

Uncomplicated peptic ulcer in the UK: trends from 1997 to 2005

BACKGROUND

Few studies have examined the incidence of uncomplicated peptic ulcer or the trends in factors affecting its incidence.

AIM

To estimate the incidence rate of uncomplicated peptic ulcer in the UK from 1997 to 2005 and report temporal changes in the main known preventive and risk factors.

METHODS

Population-based cohort study of 1 049 689 patients enrolled in The Health Improvement Network in the UK. We estimated the incidence rate of uncomplicated peptic ulcer and evaluated temporal trends in demographic characteristics and prescription patterns for various anti-inflammatory and gastroprotective agents.

RESULTS

Overall uncomplicated peptic ulcer incidence was 0.75 cases per 1000 persons-years, declining from 1.1 to 0.52 cases per 1000 person-years between 1997 and 2005. Distributions of age, gender and alcohol habits were similar in 1997 and 2005. The proportion of documented Helicobacter pylori-negative cases increased from 5% to 12%. Monthly prevalence of subjects with prescriptions for traditional non-aspirin NSAIDs changed from 7.7% to 6.8%, Coxibs from 0% to 0.7%, and proton pump inhibitors (PPIs) from 2.4% to 7.4%. The proportion of subjects on prescription NSAIDs on PPIs increased continuously over time.

CONCLUSION

A reduction in H. pylori-related peptic ulcers, changing patterns in NSAID use and increasing PPI use may have contributed to a decline in uncomplicated peptic ulcer incidence in the UK.

Association between aspirin and upper gastrointestinal complications: systematic review of epidemiologic studies

AIMS

Because of the widespread use of aspirin for prevention of cardiovascular diseases, side-effects associated with thromboprophylactic doses are of interest. This study summarizes the relative risk (RR) for serious upper gastrointestinal complications (UGIC) associated with aspirin exposure in general and with specific aspirin doses and formulations in particular.

METHODS

After a systematic review, 17 original epidemiologic studies published between 1990 and 2001 were selected according to predefined criteria. Heterogeneity of effects was explored. Pooled estimates were calculated according to different study characteristics and patterns of aspirin use.

RESULTS

The overall relative risk of UGIC associated with aspirin use was 2.2 (95% confidence interval (CI): 2.1, 2.4) for cohort studies and nested case-control studies and 3.1 (95% CI: 2.8, 3.3) for non-nested case-control studies. Original studies found a dose-response relationship between UGIC and aspirin, although the risk was still elevated for doses lower or up to 300 mg day(-1). The summary RR was 2.6 (95% CI: 2.3, 2.9) for plain, 5.3 (95% CI: 3.0, 9.2) for buffered, and 2.4 (95% CI: 1.9, 2.9) for enteric-coated aspirin formulations.

CONCLUSIONS

Aspirin was associated with UGIC even when used at low doses or in buffered or enteric-coated formulations. The latter findings may be partially explained by channeling of susceptible patients to these formulations.

Relative risk of upper gastrointestinal complications among users of acetaminophen and nonsteroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been associated with an increase in upper gastrointestinal complications. There is no agreement, however, on whether all conventional NSAIDs have a similar relative risk (RR), and epidemiologic data are limited on acetaminophen. We studied the association between these medications and the risk of upper gastrointestinal bleed/perforation in a population-based cohort of 958,397 persons in the United Kingdom between 1993 and 1998. Our nested case-control analysis included 2,105 cases and 11,500 controls. RR estimates were adjusted for several factors known to be associated with upper gastrointestinal bleed/perforation. Compared with non-users, users of acetaminophen at doses less than 2 gm did not have an increased risk of upper gastrointestinal complications. The adjusted RR for acetaminophen at doses greater than 2 gm was 3.6 [95% confidence interval (95% CI) = 2.6-5.1]. The corresponding RRs for low/medium and high doses of NSAIDs were 2.4 (95% CI = 1.9-3.1) and 4.9 (95% CI = 4.1-5.8). The RR was 3.1 (95% CI = 2.5, 3.8) for short plasma half-life, 4.5 (95% CI = 3.5-5.9) for long half-life, and 5.4 (95% CI = 4.0-7.1) for slow-release formulations of NSAIDs. After adjusting for daily dose, the differences in RR between individual NSAIDs tended to diminish except for apazone. Users of H2 receptor antagonists, omeprazole, and misoprostol had RRs of 1.4 (95% CI = 1.2-1.8), 0.6 (95% CI = 0.4-0.9), and 0.6 (95% CI = 0.4-1.0), respectively. Among NSAID users, use of nitrates was associated with an RR of 0.6 (95% CI = 0.4-1.0).

Steroids and risk of upper gastrointestinal complications

Most antiinflammatory drugs have been associated with an increase in upper gastrointestinal complications. However, the literature on steroids is more limited than that on nonsteroidal antiinflammatory drugs (NSAIDs). To estimate the risk of upper gastrointestinal complications associated with use of steroids alone and in combination, a nested case-control analysis was conducted on the General Practice Research Database from the United KINGDOM: The authors identified 2,105 cases of upper gastrointestinal complications and 11,500 controls between 1993 and 1998. The adjusted odds ratios associated with current use of oral steroids were 1.8 (95% confidence interval (CI): 1.3, 2.4) for upper gastrointestinal complications overall and 2.4 (95% CI: 1.7, 3.4) for gastric and 1.2 (95% CI: 0.8, 1.9) for duodenal damage. Steroids were similarly associated with bleeding (odds ratio (OR) = 1.8; 95% CI: 1.3, 2.4) and perforations (OR = 1.6; 95% CI: 0.9, 3.1). Simultaneous use of steroids with low-medium and high NSAID doses, respectively, produced odds ratios of 4.0 (95% CI: 1.3, 12.0) and 12.7 (95% CI: 6.2, 26.1), compared with users of none. Whenever possible, antiinflammatory drugs should be given in monotherapy and at the lowest effective dose in order to reduce the risk of upper gastrointestinal complications.

Neural tube defects in relation to use of folic acid antagonists during pregnancy

Periconceptional folic acid supplementation reduces the risk of neural tube defects (NTDs). To determine whether periconceptional exposure to folic acid antagonists (FAAs) might therefore increase the risk of NTDs, the authors examined data from an ongoing case-control study of birth defects (1979-1998) in the United States and Canada. They compared data on 1,242 infants with NTDs (spina bifida, anencephaly, and encephalocele) with data from a control group of 6,660 infants with malformations not related to vitamin supplementation. Mothers were interviewed within 6 months of delivery about demographic, reproductive, medical, and behavioral factors and about medication use. The adjusted odds ratios of NTDs related to exposure to FAAs (including carbamazepine, phenobarbital, phenytoin, primidone, sulfasalazine, triamterene, and trimethoprim) during the first or second months after the last menstrual period, compared with no use in either month, were 2.8 (95% confidence interval: 1.7, 4.6) for FAAs as a group, 4.8 (95% confidence interval: 1.5, 16.1) for trimethoprim (based on five exposed cases), and 6.9 (95% confidence interval: 1.9, 25.7) for carbamazepine (six exposed cases). These results are adjusted for region, interview year, periconceptional folic acid supplementation, maternal age, weight, education, and infections early in pregnancy. These findings suggest that a number of FAAs may increase NTD risk, and they provide estimates of risk for selected drugs.

Epidemiologic assessment of the safety of conventional nonsteroidal anti-inflammatory drugs

The use of conventional nonsteroidal anti-inflammatory drugs (NSAIDs) has been associated with upper gastrointestinal bleeding and perforation (UGIB), acute liver injury, acute renal injury, heart failure, and adverse reproductive outcomes. This article summarizes the effects of various factors, such as NSAID dose, duration of treatment, patient age, and ulcer history, on the incidences of these adverse side effects. We used the UK General Practice Research Database to study further the principal safety concern related to NSAIDs, namely, UGIB.

The risk of upper gastrointestinal complications associated with nonsteroidal anti-inflammatory drugs, glucocorticoids, acetaminophen, and combinations of these agents

Most anti-inflammatory drugs have been associated with an increased risk of serious upper gastrointestinal complications. Epidemiological studies have estimated the magnitude of the risk for specific anti-inflammatory drugs. The risk of upper gastrointestinal tract bleeding or perforation increases around twofold with use of oral steroids or low dose aspirin, and increases around fourfold with use of nonaspirin nonsteroidal anti-inflammatory drugs. Acetaminophen at daily doses of 2000 mg and higher has also been associated with an increased risk. Overall, the risk is dose dependent and is greater with more than one anti-inflammatory drug taken simultaneously. Hence, whenever possible, anti-inflammatory drugs should be given in monotherapy and at the lowest effective dose in order to reduce the risk of serious upper gastrointestinal complications.

Folic acid antagonists during pregnancy and the risk of birth defects

BACKGROUND

Multivitamin supplementation in pregnant women may reduce the risks of cardiovascular defects, oral clefts, and urinary tract defects in their infants. We evaluated whether the folic acid component of multivitamins is responsible for the reduction in risk by examining the associations between maternal use of folic acid antagonists and these congenital malformations.

METHODS

We compared data on exposure to folic acid antagonists that act as dihydrofolate reductase inhibitors and to certain antiepileptic drugs for 3870 infants with cardiovascular defects, 1962 infants with oral clefts, and 1100 infants with urinary tract defects with data for 8387 control infants with malformations the risk of which is not reduced after vitamin supplementation. Mothers were interviewed within six months after delivery about their medication use.

RESULTS

The relative risks of cardiovascular defects and oral clefts in infants whose mothers were exposed to dihydrofolate reductase inhibitors during the second or third month after the last menstrual period, as compared with infants whose mothers had no such exposure, were 3.4 (95 percent confidence interval, 1.8 to 6.4) and 2.6 (95 percent confidence interval, 1.1 to 6.1), respectively. The relative risks of cardiovascular defects, oral clefts, and urinary tract defects after maternal exposure to antiepileptic drugs were 2.2 (95 percent confidence interval, 1.4 to 3.5), 2.5 (95 percent confidence interval, 1.5 to 4.2), and 2.5 (95 percent confidence interval, 1.2 to 5.0), respectively. Use of multivitamin supplements containing folic acid diminished the adverse effects of dihydrofolate reductase inhibitors, but not that of antiepileptic drugs.

CONCLUSIONS

Folic acid antagonists, which include such common drugs as trimethoprim, triamterene, carbamazepine, phenytoin, phenobarbital, and primidone, may increase the risk not only of neural-tube defects, but also of cardiovascular defects, oral clefts, and urinary tract defects. The folic acid component of multivitamins may reduce the risks of these defects.

Association between nonsteroidal anti-inflammatory drugs and upper gastrointestinal tract bleeding/perforation: an overview of epidemiologic studies published in the 1990s

BACKGROUND

In the last decades, studies have estimated the upper gastrointestinal tract bleeding/perforation (UGIB) risk associated with individual nonsteroidal anti-inflammatory drugs (NSAIDs). Later analyses have also included the effect of patterns of NSAID use, risk factors for UGIB, and modifiers of NSAID effect.

METHODS

Systematic review of case-control and cohort studies on serious gastrointestinal tract complications and nonaspirin NSAIDs published between 1990 and 1999 using MEDLINE. Eighteen original studies were selected according to predefined criteria. Two researchers extracted the data independently. Pooled relative risk estimates were calculated according to subject and exposure characteristics. Heterogeneity of effects was tested and reasons for heterogeneity were considered.

RESULTS

Advanced age, history of peptic ulcer disease, and being male were risk factors for UGIB. Nonsteroidal anti-inflammatory drug users with advanced age or a history of peptic ulcer had the highest absolute risks. The pooled relative risk of UGIB after exposure to NSAIDs was 3.8 (95% confidence interval, 3.6-4.1). The increased risk was maintained during treatment and returned to baseline once treatment was stopped. A clear dose response was observed. There was some variation in risk between individual NSAIDs, though these differences were markedly attenuated when comparable daily doses were considered.

CONCLUSIONS

The elderly and patients with a history of peptic ulcer could benefit the most from a reduction in NSAID gastrotoxicity. Whenever possible, physicians may wish to recommend lower doses to reduce the UGIB risk associated with all individual NSAIDs, especially in the subgroup of patients with the greatest background risk.

Association of maternal short stature with stunting in Mexican children: common genes vs common environment

OBJECTIVE

To evaluate the association between stunting in children and maternal short stature, controlling for potential environmental confounders.

DESIGN

1988 Mexico National Nutrition Survey.

SETTING

Mexico

SUBJECTS

The final sample size was 4663 pairs of children (<5 y) and their mothers (12-49 y) from a total of 13 236 surveyed houses.

MAIN OUTCOME MEASURES

Stunting (height-for-age Z-scores <-2).

RESULTS

The prevalence of stunting in children was 19%, and 10% of the mothers exhibited short stature (<145 cm). In the crude analysis, mothers with short stature were significantly more likely to have stunted children (odds ratio (OR)=4.0; 95% confidence interval (CI)=3.2-4.8; P-value <0.001). In a multiple logistic regression model the OR for child stunting was reduced, but remained significant OR=2.0; 95% CI=1.6-2.6; P-value <0.001) after adjustment for region, urban/rural residence, socio-economic status, household size, child age and presence of infection in the past 14 d, and maternal age, body mass index (BMI), and educational level. Adjusted ORs varied between regions (Mexico City, OR=3.9; North Mexico, OR=3. 1; Central Mexico, OR=2.0; South Mexico, OR=1.6. Comparison of crude vs adjusted estimates pointed to regional differences in the proportion of association between maternal and child short statures explained by environmental determinants.

CONCLUSIONS

Maternal stature, reflecting her potential height and early environment, appeared to contribute to child height independently of the shared risk factors that could affect stature. Nonetheless, we could explain much of the association between stunting in children and maternal short stature by environmental factors, and part of the residual variability may be due to unmeasured determinants. Regional differences pointed to a predominance of environmental factors in explaining child stunting in poorer regions.

Childhood malnutrition and postwar reconstruction in rural El Salvador: a community-based survey

CONTEXT

The 1992 peace settlement that ended the civil war in El Salvador included land redistribution and other provisions designed to improve the socioeconomic status of ex-combatants and vulnerable civilians.

OBJECTIVE

To describe associations between postwar social and economic assistance programs, especially land reform, and current child health status as reflected by nutrition in a population of resettled rural refugees.

DESIGN

A population-based cross-sectional survey of child nutritional status and principal elements of the reconstruction process.

SETTING

A single rural municipality in northern El Salvador.

PARTICIPANTS

A representative sample of 761 children younger than 5 years, living in 27 villages.

MAIN OUTCOME MEASURE

Prevalence of stunting (low height for age) in children younger than 5 years.

RESULTS

Prevalence of stunting was 32.4%. Stunting was significantly more prevalent among children whose families cultivated less land (odds ratio [OR] for stunting per additional hectare of redistributed land cultivated, 0.64; 95% confidence interval [CI], 0.44-0.93). Less than half of newly transferred land was being cultivated by its owners. Most of the children (84.7%) lived in families cultivating 2 hectares or less of redistributed land. Stunting was also more prevalent among children whose households lacked piped water (adjusted OR, 2.72; 95% CI, 1.87-3.96) vs those who had had piped water since before the cease-fire.

CONCLUSIONS

Malnutrition, particularly stunting, persisted at high levels and was strongly associated with delay in full cultivation of redistributed land and in provision of water.