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Society for Epidemiologic Research (SER) Presidential Addresses

SER President Discusses Issues Related to Epidemiology and Policy

Szklo Underscores Importance of Biology in Epidemiology

“There is a need for “more incisive” discussion of the concepts and methods of epidemiology relevant to policy formulation. This was the theme of the presidential address at the recent SER meeting in Birmingham. Outgoing president Moyses Szklo presented his views on some of the issues related to the interface between epidemiology and policy and on the importance of biological thinking in all phases of epidemiologic research.

Why Discuss?

In explaining the need for such discussion, Dr. Szklo noted that the contributions of statistical methods to epidemiology, which have added enormously to the growth of epidemiology, have received considerable attention in graduate programs. However, the specific relevance of these methods to policy recommendations has not received comparable attention. He attributed this to the fact that epidemiologic expertise in recent decades has tended to move away from service-oriented agencies such as health departments and has gravitated to academic institutions where the pressure to develop policy is less.

Issues Worth Discussing

In his view, the well known concepts and methods of epidemiology... “acquire a special meaning when seen in the specific context of the policy implications of research.” Among the examples he cited was in the area of determining causality. Identifying a truly causal association is important for establishing etiology and for designing primary prevention strategies. However, perhaps less well appreciated is the fact that it is also important for epidemiologists to help distinguish between valid, non-causal associations and truly spurious ones. The former may be useful for identifying risk groups for secondary prevention purposes such as screening.


Dr. Szklo also focused on the importance of replicability in establishing whether or not reported associations are truly causal. Noting the potential contributions of meta-analysis in this regard, he warned the audience that published studies may not be representative of all findings because of the documented bias towards publishing positive findings. One remedy proposed for this problem is the establishment of registries which would track studies regardless of outcome.

Another warning he gave was that discrepancies between study findings were not necessarily evidence of lack of association. Study populations are not homogeneous. In considering policy recommendations, prevention strategies might be able to be tailored to subgroups at genuine increased risk.


Dr. Szklo criticized the assessment of interaction only for statistical modeling purposes. He underlined the importance of the additive model of interaction for public health purposes and proposed that its effects should be systematically reported regardless of its usefulness for other methodologic purposes.

Weak Associations

Weak associations are difficult for epidemiology to deal with, yet their importance may be considerable in public health terms when disease is relatively common and exposure widespread. Meta-analysis can help by pooling results from several studies; however, small sample size is also a risk factor for non-submission or non-publication of results. “...Clearly a rethinking of the implications of insufficient statistical power due to weak associations is in order in this era of meta-analysis,” according to Szklo.

Epi and Biology

Dr. Szklo closed his talk by emphasizing the need to strengthen biological thinking in epidemiologic research. He identified several components of epidemiologic work which can be enhanced by sound biological knowledge. For example, problems in exposure misclassification which tend to bias studies towards a lower risk estimate may result in the failure to detect weak associations which could have public health importance. Likewise, the failure of some reported risk factors to explain a larger share of disease occurrence might be remedied in part by more accurate classification of disease outcomes.

Kelsey Committee

Dr. Szklo noted that a committee headed by Jennifer Kelsey of Columbia has been formed to examine the need for strengthening biological thinking in epidemiology. If this committee finds there is a need, he believes the profession should move swiftly to discuss ways in which this can be accomplished. This will be important to increase the credibility of epidemiology, to improve its ability to establish causal relationships, and ultimately to make more incisive contributions to establishing health policies, he said.

Published July 1989 

Postscript 2000

            The decade that followed this presidential address has seen the confirmation of the importance of both biologic thinking and translational activities in epidemiology. The extraordinary growth of molecular biology

and genetics has led to a proliferation of genetic epidemiology studies aiming at elucidating the genetic etiology of a number of disease areas, particularly those representing the major killers, coronary heart disease and cancer. An important challenge is that the focus has been on isolated genes or polymorphisms, rather than on the more interesting gene-environment interactions, which become of paramount interest given the fact that pure genetic etiology cannot explain more than a small fraction of disease in the population. Another challenge posed by the development of genetic epidemiology studies relates to the strategy for prevention at the population-level. Hopefully, identification of highly susceptible individuals on a genetic basis will not lead to a shift from the clearly superior population-based to the high risk strategy in prevention.

            The 1990s also saw an increase in the use of epidemiologic data for policy purposes, with the best example of this given by the anti-tobacco fight. Meta-analysis has been increasingly used as an instrument for the shaping of health policies and the development of recommendations pertaining to public health strategies. An example is the recent meta-analysis of results of studies dealing with treatment of nicotine dependence, which has led to a series of recommendations from the Surgeon General office published a few months ago. The strengthening of the Cochrane database is yet another important development in the implementation of evidence-based public health and medical actions.

            In summary, the last decade has seen strong movements towards integrating biologic thinking into epidemiologic research and translating its findings into public health action. From the latter viewpoint, epidemiology seems to be moving back to its origins as a basic tool of public health, meant to act as the scientific basis for the development of health policy.

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