One of the environmental factors which gained much attention during the last decades, is vitamin D. A poor exposure to either vitamin D or sunlight, its most important inducer, has been associated with a high risk of developing MS [2].
Thus, internal validity is limited by a poor exposure metric.
Interferences through a poor exposure of the tumour, sudden movements of the patient or gagging become evident and obscured the depiction of the lymphatic drainage into the representative main draining level of a primary tumour.
Therefore, it is difficult to know if the lack of an association between leukaemia and employment for Endicott Johnson may have been a result of poor exposure assessment or a result of no exposure to certain carcinogens.
Two groups of healthy controls were analyzed, which included medical students (HCA), who led a lifestyle marked by poor exposure to sunlight and irregular dietary habits, and a group of healthy subjects from the same locality (HCB).
With Method 1, the estimation of HR ¯ t was biased with HP and L W A u, but more with HP; the estimation of HR ¯ a t was biased with L W A a. Whatever the model applied, HR ¯ t (HP, L W A u ) and HR ¯ a t (LWA a ) were underestimated, i.e. a poor prognostic exposure effect tended to be ignored and a no exposure effect tended to become a protective one.
Previous studies had limited sample sizes, poor exposure characterization, and a few single nucleotide polymorphisms (SNPs) tested in candidate genes.
17 Caries remains a major oral health problem among the elderly for various reasons: the increase in treatment and maintenance of teeth rather than their extraction; age-related salivary changes; a poor diet; exposure of the root surface by gingival recession; and a greater likelihood of drug treatment with xerostomia as a side effect.
The first study using octreotide LAR, reported by Yuen et al (2002), was controversial and criticable because the selected patients had a very short survival (1.9 months in the control group (n=35) vs 2 months in the octreotide group (n=35)), probably due to a high proportion of advanced HCC with CLIP score >4 and a poor treatment exposure.
Large sample size is important, but when large sample size comes with poor exposure classification, the consequence is a statistically precise, biased estimate of effect.
The problems include poor media coverage on the air and in print, lack of sponsorship, outdated presentation, the fractured nature of the global circuit, poor exposure of top athletes, and lack of appeal to youngsters.
