Epidemiology
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Few studies have examined associations of geographically proximal cigarette prices with within-person changes in smoking outcomes or assessed interactions between cigarette prices and smoking bans. ⋯ Results underscore the importance of local prices, but not hospitality smoking bans, in influencing older adults' smoking behaviors.
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Fertility treatment includes hormonal stimulation of the woman and in vitro manipulation of gametes and embryos that may influence prenatal brain development. We aimed to investigate the association between fertility treatment and childhood epilepsy, including specific types of treatment and indications, as well as subtypes of epilepsy. ⋯ Children conceived by ovulation induction or intrauterine insemination with clomiphene citrate may be at slightly increased risk of childhood epilepsy. Furthermore, children conceived by in vitro fertilization or intracytoplasmic sperm injection may be at slightly increased risk of idiopathic generalized epilepsy.
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Instrumental variables (IV) are used to draw causal conclusions about the effect of exposure E on outcome Y in the presence of unmeasured confounders. IV assumptions have been well described: (1) IV affects E; (2) IV affects Y only through E; (3) IV shares no common cause with Y. Even when these assumptions are met, biased effect estimates can result if selection bias allows a noncausal path from E to Y. ⋯ By applying inverse probability of selection weights, we were able to eliminate the selection bias. IV approaches may protect against unmeasured confounding but are not immune from selection bias. Inverse probability of selection weights used with IV approaches can minimize bias.