The effect of smoking nicotine tobacco versus smoking deprivation on motion sickness

BACKGROUND: The experienced smoker maintains adequate nicotine levels by 'puff-by-puff self-control' which also avoids symptomatic nauseating effects of nicotine overdose. It is postulated that there is a varying 'dynamic threshold for nausea' into which motion sickness susceptibility provides an objective toxin-free probe. Hypotheses were that: (i) nicotine promotes motion sickness whereas deprivation protects; and (ii) pleasurable effects of nicotine protect against motion sickness whereas adverse effects of withdrawal have the opposite effect. METHODS: Twenty-six healthy habitual cigarette smokers (mean±SD) 15.3±7.6cigs/day, were exposed to a provocative cross-coupled (coriolis) motion on a turntable, with sequences of 8 head movements every 30s. This continued to the point of moderate nausea. Subjects were tested after either ad-lib normal smoking (SMOKE) or after overnight deprivation (DEPRIV), according to a repeated measures design counter-balanced for order with 1-week interval between tests. RESULTS: Deprivation from recent smoking was confirmed by objective measures: exhaled carbon monoxide CO was lower (P<0.001) for DEPRIV (8.5±5.6ppm) versus SMOKE (16.0±6.3ppm); resting heart rate was lower (P<0.001) for DEPRIV (67.9±8.4bpm) versus SMOKE (74.3±9.5bpm). Mean±SD sequences of head movements tolerated to achieve moderate nausea were more (P=0.014) for DEPRIV (21.3±9.9) versus SMOKE (18.3±8.5). DISCUSSION: Tolerance to motion sickness was aided by short-term smoking deprivation, supporting Hypothesis (i) but not Hypothesis (ii). The effect was was approximately equivalent to half of the effect of an anti-motion sickness drug. Temporary nicotine withdrawal peri-operatively may explain why smokers have reduced risk for postoperative nausea and vomiting (PONV).

Separating the effects of ethnicity and socio-economic status on sleep practices of 6- to 7-month-old infants

Infant sleep undergoes significant re-organization throughout the first 12 months of life, with sleep quality having significant consequences for infant learning and cognitive development. While there has been great interest in the neural basis and developmental trajectories of infant sleep in general, relatively little is known about individual differences in infant sleep and the socio-economic and cultural sources of that variability. We investigated this using questionnaire sleep data in a large, unique multi-ethnic sample of 6-7 month-olds (n=174), with families from South Asian ethnic groups in the UK (Indian, Pakistani and Bangladeshi) being especially well represented. Consistent with previous data from less variable samples, no effects of SES on sleep latency or nocturnal sleep duration emerged. However, perinatal risk factors and ethnic differences did predict daytime sleep, sleep fragmentation and sleep-onset time. While these results should be interpreted with caution due to several limitations, they likely demonstrate that even when socio-economic status and ethnicity are much less confounded than in previous studies, they have a surprisingly limited impact on individual differences in sleep patterns in young infants.