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Self-reported and measured height and weight were obtained from a representative sample of 1,598 persons in Auckland, New Zealand during 1982. The accuracy of the self-reported data and its effect on the misclassification of relative weight, as measured by Quetelet index, were examined. The finding that for most participants (75%), self-reported measures were no more than 3.5 cm from their measured height and 2.4 kg from their measured weight indicates that self-reports have a high degree of accuracy. However, the participants consistently overestimated their height and underestimated their weight, resulting in an underestimation of relative weight. This would have little effect on analyses using the self-reported relative weight measures as a continuous covariate, but misclassification would occur when using relative weight as a categorical variable. The sensitivities and specificities associated with categorized self-reported relative risks that have been calculated from relative weight derived from self-reported height and weight.

The relation between the plasma level of 25-hydroxyvitamin D3, the main metabolite of sun-induced vitamin D, and myocardial infarction (MI) was investigated in a community-based case-control study. Some 179 MI patients presenting to hospital within 12 hours of the onset of symptoms were individually matched with controls by age, sex and date of blood collection. MI patients had significantly lower mean 25-hydroxyvitamin D3 levels than controls (32.0 versus 35.5 nmol/L; p = 0.017), with the case-control differences being greatest in winter and spring. The relative risk of MI for subjects with 25-hydroxyvitamin D3 levels equal to or above the median was 0.43 (95% confidence limits = 0.27, 0.69) compared to subjects below the median. The decrease in MI risk associated with raised vitamin D3 levels was observed in all seasons. These results provide support for the hypothesis that increased exposure to sunlight is protective against coronary heart disease.

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Objective-To estimate the relative risk of stroke associated with exposure to environmental tobacco smoke (ETS, passive smoking) and to estimate the risk of stroke associated with current smoking (active smoking) using the traditional baseline group (never-smokers) and a baseline group that includes lifelong nonsmokers and long-term (>10 years) ex-smokers who have not been exposed to ETS. Design and setting-Population-based case-control study in residents of Auckland, New Zealand. Subjects-Cases were obtained from the Auckland stroke study, a populationbased register of acute stroke. Controls were obtained from a cross-sectional survey of major cardiovascular risk factors measured in the same population. A standard questionaire was administered to patients and controls by trained nurse interviewers. Results-Information was available for 521 patients with first-ever acute stroke and 1851 community controls aged 35-74 years. After adjusting for potential confounders (age, sex, history of hypertension, heart disease, and diabetes) using logistic regression, exposure to ETS among non-smokers and long-term ex-smokers was associated with a significantly increased risk of stroke (odds ratio (OR) = 1.82; 95% confidence interval (95% CI) = 1.34 to 2.49). The risk was significant in men (OR = 2.10; 95% CI = 1.33 to 3.32) and women (OR = 1.66; 95% CI = 1.07 to 2.57). Active smokers had a fourfold risk of stroke compared with people who reported they had never smoked cigarettes (OR = 4.14; 95% CI = 3.04 to 5.63); the risk increased when active smokers were compared with people who had never smoked or had quit smoking more than 10 years earlier and who were not exposed to ETS (OR = 6.33; 95% CI = 4.50 to 8.91). Conclusions-This study is one of the few to investigate the association between passive smoking and the risk of acute stroke. We found a significantly increased risk of stroke in men and in women. This study also confirms the higher risk of stroke in men and women who smoke cigarettes compared with non-smokers. The stroke risk increases further when those who have been exposed to ETS are excluded from the non-smoking reference group. These findings also suggest that studies investigating the adverse eVects of smoking will underestimate the risk if exposure to ETS is not taken into account. (Tobacco Control 1999;8:156-160)