OBJECTIVE: To examine the validity of self-reported information on obesity and high blood pressure (HBP) in relation to gender and age, and to explore the impacts of their misclassi®cation on the association between obesity and HBP. DESIGN: Community based cross-sectional study. SUBJECTS: 1791 adult subjects living in Humboldt, Saskatchewan, Canada. MEASUREMENTS: Objectively measured HBP was positive if systolic blood pressure (BP) was !140 mm Hg, diastolic BP was !90 mm Hg or the subject was currently using antihypertensive medication. Self-reported HBP was positive if the subjects gave an af®rmative response to the question:`Has a doctor ever said you had high blood pressure?' Body mass index (BMI) was calculated as weight (kg)aheight (m) 2 . Obesity was de®ned as a BMI b 27 kgam 2 . Measured obesity and reported obesity were based on measured and self-reported information on height and weight, respectively. RESULTS: The sensitivity of self-reported HBP was low, and was lower for men than for women, and for younger subjects than for older subjects. The speci®city was similar for both genders. Obese individuals had higher sensitivity and lower speci®city than non-obese individuals. The differential misclassi®cation of self-reported HBP caused a bias away from the null when the relative risk for HBP in relation to obesity was estimated. CONCLUSIONS: As a result of the gender-and age-related misclassi®cation of self-reported HBP, the modi®cation role of gender and age on the association between obesity and HBP could be altered. The bias caused by self-reported obesity was relatively small and was either toward or away from the null.

We examined the possible impact of tonsillectomy or adenoidectomy (T/A) on the relationship between environmental tobacco smoke (ETS) exposure and respiratory outcomes. This study was conducted in Humboldt, Saskatchewan, in 1993. The target population included all residents aged 6-17 yrs. Of the 1,019 eligible subjects, 892 participated (88%). Estimates of ETS exposure were based on the reported smoking habits of the children's household members. We defined current cough as a positive response to the question: "Does this child usually have a cough?". Information also included morning cough, night cough and a history of T/A. For children with no history of T/A, the prevalence of current cough was 8.9%, 12.2% and 14.5% for those living in families with 0, 1, and 2+ smokers respectively. The corresponding prevalence was 7.0%, 30.2% and 36.8% for children with history of T/A. Similar effects of ETS exposure were observed on morning cough and night cough. The results did not change significantly when we used various ETS measures and controlled for confounding factors. Compared to children living in nonsmoking families and without history of T/A, the adjusted odds ratio for children with a history of T/A was 7.19 (p<0.001) if they were living in families smoking >20 cigarettes x day(-1) at home. The corresponding odds ratio was only 1.64 (p=0.11) for children without a history of T/A. We concluded that children living in smoking family were more likely to cough than those living in nonsmoking families and tonsillectomy or adenoidectomy increased the apparent influence of environmental tobacco exposure on cough.