Two simple self-report measures have been used to assess the heaviness of smoking, 'number of cigarettes per day' (CPD) and 'time to the first cigarette of the day' (TTF). Little attention, however, has been given to the precise method of scoring this information. Using biochemical indicators of heaviness of smoking (alveolar carbon monoxide and cotinine), we explore the optimum data transformations for regression analysis and categorical analysis. We suggest a four category scoring scheme for both time to the first cigarette of the day (less than or equal to 5, 6-30, 31-60 and 61+ min) and average daily consumption of cigarettes (1-10, 11-20, 21-30, 31+ cigarettes) as the most powerful and practical categorical scoring of these variables. Due to possible ceiling effects on biochemical measures, we suggest using logarithmic transformations of CPD or TTF for regression or correlation analyses.

A standardised inventory of stressful life events and a bowel symptom questionnaire were administered at three month intervals for one year to 383 women who were unselected with respect to bowel symptoms. A NEO Personality Inventory was given initially to assess neuroticism. Subjects who satisfied restrictive diagnostic criteria for irritable bowel syndrome were compared with those who complained of abdominal pain plus altered bowel habits but who did not meet restrictive diagnostic criteria (functional bowel disorder) and with controls without bowel dysfunction. The irritable bowel group showed significantly higher levels of stress than the other two groups even when the confounding effects of neuroticism were statistically controlled for. Time lagged correlations showed that stress in one three month interval was significantly correlated with bowel symptoms in the subsequent three month interval for all groups. The slope of the regression line relating stress to bowel symptoms was significantly steeper for the irritable bowel group than for the other two groups at three and six months, suggesting that subjects with irritable bowel syndrome show a greater reactivity to stress. Stress scores were also significantly correlated with the number of disability days and the number of medical clinic visits for bowel symptoms.

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