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Estimation of time trends in alcohol consumption for recent years in Switzerland is complicated by the fact that the assessment method was changed from personal interview to self-administered questionnaire. With a large-scale study which compared the two methods, it is possible in estimating time trends to allow for adjustment of the effects produced by this change of assessment method. Results indicate that alcohol consumption decreased by about 17% between 1987 and 1993. This decrease was observed uniformly for both genders and all age-groups, which supports the basic assumptions of Skog's revised theory of Ledermann (1985). Personal interviews resulted in considerably higher reported alcohol consumption (+22%) than written questionnaires.

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OBJECTIVE: To test the hypothesis that exposure to pet birds increases risk of developing lung cancer. DESIGN: Case-control study. Computerised interviews were used to assess previous exposure to pets and other risk factors for lung cancer. SETTING: Three major hospitals treating respiratory disease in former West Berlin. SUBJECTS: All people newly diagnosed as having primary malignant neoplasm of the trachea, bronchi, or lung who were 65 or younger and control subjects matched for age and sex from the general population of former West Berlin. 279 cases and 635 controls qualified for the study; 239 cases and 429 controls participated. MAIN OUTCOME MEASURES: Odds ratio of developing lung cancer according to whether or not pet birds were kept and the duration of keeping pet birds. RESULTS: In addition to the risk of lung cancer imposed by smoking, passive smoking, and occupational exposure to carcinogens, an increased relative risk of 2.14 (95% confidence interval 1.35 to 3.40) was found among people exposed to pet birds. The adjusted odds ratio for exposures longer than 10 years was 3.19 (1.48 to 8.21). CONCLUSIONS: Avian exposure seems to carry a risk of lung cancer. Until the pathogenesis is understood, long term exposure to pet birds in living areas should be avoided, especially among people at high risk of developing lung cancer.

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Omitted variable bias is discussed in the context of linear models. It is shown that the effect of omitted variables can be controlled in linear models for metric dependent variables by using data from follow-up studies. Two different models for analysing such data are proposed. In the first model the omitted variables are assumed to be uncorrelated with the explanatory variables in the model and to be constant over time. These assumptions lead to a special structure of the covariance matrix of the errors over time. Efficient estimation of the parameters in the linear model has to take this special covariance matrix of the errors into account by using appropriate generalized least squares or maximum likelihood methods. In the second model the omitted variables are assumed to be time constant. Additionally, they are allowed to be correlated with the explanatory variables, that is these variables are omitted confounders in the usual epidemiological sense. It is shown that even in this case the parameters of the linear model can be estimated consistently with ordinary least squares if a follow-up study is available. The differences between the parameter estimates under the first and the second model may be used to construct a Hausman test for misspecification. The models, the estimation methods and the Hausman test are illustrated by the example that explores the determinants of serum cholesterol in German adoloscents of both sexes.

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"This article proposes new methods for modeling household fertility decisions....Specifically, we model the trivariate distribution of wife's stated desire for additional children, husband's stated desire for additional children, and subsequent fertility. In the model, the stated desire of the husband (wife) is viewed as an indicator of the husband's (wife's) latent disposition toward subsequent fertility. The husband's (wife's) disposition is allowed to depend on the wife's (husband's) disposition. The two dispositions are then combined to generate the couple's propensity for subsequent fertility. We show how such models can be estimated and tested and how the parameters can be used to assess the relative influence of each partner on the propensity." The model is tested using U.S. data from the Princeton Fertility Study for the 1950s and 1960s. The results indicate that "both husband's disposition score and wife's disposition score affect the propensity score, and, under some additional assumptions, that husbands and wives have equal relative influence on the propensity."

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The author compares aspects of voluntary and involuntary sample surveys in West Germany. "The German microcensus as a non-voluntary survey draws a random sample from the total population which includes persons that would also respond in a voluntary survey (respondents) and persons that would not respond (non-respondents). The population of a voluntary survey, however, includes only respondents. Hence, statistical inference from a voluntary sample survey is only valid for the total population, if the population of respondents does not differ from the total population. This null hypothesis must be rejected from the comparisons of data from the German microcensus of 1985, 1986 and 1987 and corresponding voluntary test sample surveys. The discrepancies are great in central demographic and socio-economic variables such as region of residence, community size, age, marital status, income and social security." (SUMMARY IN ENG)

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