Nested Randomized Trials

Most diseases are likely to result largely from the
interplay of lifestyle and genetic factors. However, both observational
studies and randomized trials have faced major limitations
in trying to address the impact of lifestyle on health. As
large cohorts and biobanks are being developed, we need to find

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novel, efficient ways to address the effects of lifestyle interventions.
We propose that this could be done using multiple lifestyle
factorial experimental designs that combine characteristics of
randomized trials and epidemiologic studies. Randomized trials 公卫考场
of simple lifestyle interventions can be nested within large
cohorts linked to reliable registries of outcomes. Participants can
choose from a long list of simple lifestyle randomization options
and many interventions may be tested concurrently with factorial 公卫家园
randomization. Participants can tailor their own personal trial
choosing several items among long laundry lists of randomization
options. Participants are citizen-scientists rather than passive
subjects and this may be attractive in modern societies of healthconscious 公卫家园
people. These trials can use the existing machinery of
the cohort for data collection and outcome linkage at no or
minimal additional cost. We discuss a number of issues on the
implementation of multiple lifestyle factorial experimental designs, 公卫家园
as compared with the usual observational studies and
randomized trials. These include participation, the number of
allowed randomizations per participant, compliance/adherence,
power, false-negatives, false-positives, composite lifestyle effects,

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selection of outcomes, follow-up and monitoring, masking
and allocation concealment, age of participants, confounding, and
cost. The aim should be to combine carefully the strengths of
both observational epidemiology and randomized research without

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compounding their limitations.