Potential confounders

Inadvertent fetal exposure to contraceptive hormones is common, with a USA study estimating that approximately 70 000 fetuses are exposed to oral contraceptives annually.23 Most of the data on fetal outcomes relate to COC. The CEU found no studies that specifically assessed exposure through quick starting contraception. Studies are often limited by their observational nature, potential confounding factors and small sample size. Reassuringly there have been no consistent findings of specific fetal abnormalities.

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The different sources of potential confounding in time series studies of air pollution and mortality can be broadly classified as either measured or unmeasured. Important measured confounders include weather variables such as temperature and dewpoint temperature. Daily temperature measurements are readily available for metropolitan areas in the USA and numer- ous studies have demonstrated a relationship between temperature and mortality which is gen- erally positive for warm summer days and negative for cold winter days (e.g. Curriero et al. (2002)).

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The critical role of the NMMAPS in the development of the air quality standards attracted intense scrutiny from the scientific community and industry groups regarding the statistical models that are used and the methods that are employed for adjusting for potential confound- ing. Confounding occurs when an attribute that is associated with an outcome is also associated with the exposure of interest but is not a result of the exposure. In time series studies, we are primarily concerned with potential confounding by factors that vary on similar timescales as pollution or mortality.

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Another limitation of the literature is that minorities have been dramatically under- represented in psycho-oncology research (Anderson, 1992). Further, although the research demonstrates the importance of the spousal relationship during the cancer experience, there is a lack of controlled research concerning couples or family interventions. Finally, a crucial question that remains unanswered is determining what these findings mean in terms of clinical intervention and care.

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Case studies for emerging risks in the second section include evidence-based precautionary interventions to safeguard blood supplies, the evaluation of nanoparticle deposition in the lung and nasal airways and the discourse surrounding emerging potential health risks of genetically modified animals consumed as food. The third chapter by Tyshenko et al.

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In practice, signatures that predict toxicity or efficacy can be identified afterwards. For example, therapies targeting the Epidermal Growth Factor Receptor have been first approved before it was demonstrated that mutations in KRAS cancer gene were associated to failures of the relevant therapies in metastatic colorectal carcinoma. This example shows that well-designed retrospective analysis of data from prospective randomized controlled trials can bring forward effective treatments to biomarker defined subgroups of patients in a timely manner.

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