These findings give some support to the hypothesis that the IGF axis is involved in the pathogenesis of ischemic stroke.

An understanding of the origin of cancer is critical for cancer prevention and treatment. Complex biological mechanisms promote carcinogenesis, and there is increasing evidence that pregnancy‐related exposures influence foetal growth cell division and organ functioning and may have a long‐lasting impact on health and disease susceptibility in the mothers and offspring. Nulliparity is an established risk factor for breast, ovarian, endometrial and possibly pancreatic cancer, whilst the risk of kidney cancer is elevated in parous compared with nulliparous women. For breast, endometrial and ovarian cancer, each pregnancy provides an additional risk reduction. The associations of parity with thyroid and colorectal cancers are uncertain. The timing of reproductive events is also recognized to be important. Older age at first birth is associated with an increased risk of breast cancer, and older age at last birth is associated with a reduced risk of endometrial cancer. The risks of breast and endometrial cancers increase with younger age at menarche and older age at menopause. The mechanisms, and hormone profiles, that underlie alterations in maternal cancer risk are not fully understood and may differ by malignancy. Linking health registries and pooling of data in the Nordic countries have provided opportunities to conduct epidemiologic research of pregnancy exposures and subsequent cancer. We review the maternal risk of several malignancies, including those with a well‐known hormonal aetiology and those with less established relationships. The tendency for women to have fewer pregnancies and at later ages, together with the age‐dependent increase in the incidence of most malignancies, is expected to affect the incidence of pregnancy‐associated cancer.

Several studies have suggested that breastfeeding has a long-term influence on brain development. However, interpretation of these findings is complicated by the presence of many potential confounding factors. Only a few studies have examined infants before 1 y of age, although very early assessment might reduce the role of environmental influence. We investigated the association between exclusive breastfeeding and three developmental milestones related to general and fine motor skills and early language development at the age of 8 mo. We followed 1656 healthy, singleton, term infants, with a birthweight of at least 2500 g, born between May 1991 and February 1992 in Aarhus, Denmark. Information was collected at 16 wk gestation, at delivery and when the infant was 8 mo old. Motor skills were evaluated by measurement of crawling and pincer grip. Early language development was defined as the ability to babble in polysyllables. The proportion of infants who mastered the specific milestones increased consistently with increasing duration of breastfeeding. The relative risk for the highest versus the lowest breastfeeding category was 1.3 (95% CI: 1.0-1.6) for crawling, 1.2 (95% CI: 1.1-1.3) for pincer grip and 1.5 (95% Cl: 1.3-1.8) for polysyllable babbling. Little change was found after adjustment for confounding. In conclusion, our data support the hypothesis that breastfeeding benefits neurodevelopment.

Seasonal variation in occurrence is a common feature of many diseases, especially those of infectious origin. Studies of seasonal variation contribute to healthcare planning and to the understanding of the aetiology of infections. In this article, we provide an overview of statistical methods for the assessment and quantification of seasonality of infectious diseases, as exemplified by their application to meningococcal disease in Denmark in 1995-2011. Additionally, we discuss the conditions under which seasonality should be considered as a covariate in studies of infectious diseases. The methods considered range from the simplest comparison of disease occurrence between the extremes of summer and winter, through modelling of the intensity of seasonal patterns by use of a sine curve, to more advanced generalized linear models. All three classes of method have advantages and disadvantages. The choice among analytical approaches should ideally reflect the research question of interest. Simple methods are compelling, but may overlook important seasonal peaks that would have been identified if more advanced methods had been applied. For most studies, we suggest the use of methods that allow estimation of the magnitude and timing of seasonal peaks and valleys, ideally with a measure of the intensity of seasonality, such as the peak-to-low ratio. Seasonality may be a confounder in studies of infectious disease occurrence when it fulfils the three primary criteria for being a confounder, i.e. when both the disease occurrence and the exposure vary seasonally without seasonality being a step in the causal pathway. In these situations, confounding by seasonality should be controlled as for any confounder.

No abstract