Objective To examine associations between interpregnancy interval, the duration from the preceding birth to the conception of the next-born index child, and adverse birth outcomes using designs that adjust for measured and unmeasured factors. Methods In this prospective cohort study we used population-based Swedish registries from 1973 to 2009 to estimate the associations between interpregnancy interval (referent 18-23 months), and adverse birth outcomes [i.e., preterm birth (PTB, < 37 weeks), low birth weight (LBW, <2,500 g), small for gestational age (SGA, > 2 standard deviations below average weight for gestational age)]. Analyses included cousin- and sibling-comparisons, and postbirth intervals (ie, the interval between second- and third-born offspring predicting second-born outcomes), to address unmeasured familial confounding. Results Traditional cohort-wide analyses showed higher odds of PTB [adjusted odds ratio (aOR)=1.51, 99% CI=1.39-1.63, 5.99% PTBs)] and LBW (aOR=1.25, 99% CI=1.13-1.39, 3.32% LBW) after short interpregnancy interval (0-5 months) compared to offspring born after an interpregnancy interval of 18-23 months (3.21% PTBs, 1.92% LBW). For pregnancy intervals of 60 months or more, odds of PTB (aOR=1.51, 99% CI=1.43-1.60, 5.07% PTBs), LBW (a OR=1.61, 99% CI=1.50-1.73, 3.43% LBW births), and SGA (aOR=1.54, 99% CI=1.42-1.66, 2.49% SGA births) were also higher when compared with the reference interval (1.53% SGA). Except for PTB (aOR=1.72, 99% CI=1.26-2.35), associations were attenuated in cousin-comparisons. A small association between short interpregnancy interval and PTB remained in sibling-comparisons (aOR=1.22, 99% CI=1.11-1.35), but associations with LBW (aOR=0.83, 99% CI=0.74-0.94) and SGA (aOR=0.74, 99% CI=0.64-0.85) reversed direction. Associations between long interpregnancy interval and adverse birth outcomes remained through cousin- and sibling-comparisons. Post birth interval analyses showed familial confounding is present for short interpregnancy intervals, but supported independent associations for long interpregnancy intervals. Conclusion Familial confounding explains most of the association between short interpregnancy interval and adverse birth outcomes while associations with long interpregnancy intervals were independent of measured and unmeasured factors.

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Several marine and freshwater diatoms produce polyunsaturated aldehydes (PUA) in wound-activated processes. These metabolites are also released by intact diatom cells during algal blooms. Due to their activity in laboratory experiments, PUA are considered as potential mediators of diatom-bacteria interactions. Here, we tested the hypothesis that PUA mediate such processes in a close-to-field mesocosm experiment. Natural plankton communities enriched with Skeletonema marinoi strains that differ in their PUA production, a plankton control, and a plankton control supplemented with PUA at natural and elevated concentrations were observed. We monitored bacterial and viral abundance as well as bacterial community composition and did not observe any influence of PUA on these parameters even at elevated concentrations. We rather detected an alternation of the bacterial diversity over time and differences between the two S. marinoi strains, indicating unique dynamic bacterial communities in these algal blooms. These results suggest that factors other than PUA are of significance for interactions between diatoms and bacteria.

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BackgroundWhile compromised stress resilience constitutes a recognised risk factor for somatic and psychiatric disease development in general, the knowledge about how individual variation in vulnerability to stress may specifically influence the long-term risks of disadvantageous health behaviours is limited.MethodsIn this Swedish cohort study, we aimed to investigate the association between stress resilience in late adolescence and adult use of addictive substances. We included 9381 men with information on psychological stress resilience measured during military conscription examinations, who later responded to an extensive health survey (mean age 34.0±7.2 years) including detailed information on substance use. We modelled continuous outcomes using linear regression, binary outcomes with logistic regression and other categorical outcomes with multinomial logistic regression.ResultsWe found that low stress resilience in adolescence conferred increased risks of all studied measures of addictive behaviour. After adjusting for childhood socioeconomic information, low stress resilience was associated with adult current regular smoking (relative risk ratio: 5.85, 95% CI 4.32 to 7.93), higher nicotine dependence scores (beta: 0.76, 95% CI 0.29 to 1.23), hazardous use of alcohol (>14 alcoholic drink-equivalents per week, OR: 1.72, 95% CI 1.37 to 2.16), DSM-IV criteria for alcohol dependence (OR: 1.74, 95% CI 1.35 to 2.25), and drug use (OR: 1.77, 95% CI 1.51 to 2.08). The results remained largely unchanged after further adjustments for adult educational attainment and occupation as well as for additional conscription covariates.ConclusionLow stress resilience in late adolescence appears to be associated with an increased risk of disadvantageous and addictive health behaviours in adulthood.