To use the persontime approach to take into account changing

To use the person-time approach to take into account changing exposures involves an assumption akin to that used in crossover clinical trials. Describe this assumption and discuss how if this assumption is valid when studying smoking as an exposure.

Solution

To use the person-time approach to take into account changing exposures involves an assumption akin to that used in crossover clinical trials:

The exposure status is going to change then the associated risk is also going to produce but there will be not accumulation of risk for a given exposure because the exposure is instantaneous. This assumption is considered only valid if the exposure is going to trigger specific outcome. Smoking is an exposure that causes specific risk effects such as lung cancer, thromboembolic effects further result in cardiac arrest. These associated risks with smoking rely upon the acute or chronic exposure to “smoking”. Instantaneous smoking immediately do not trigger lung cancer but there is possible cardiac arrest as a cumulative effect & it can be described as the outcome of interest based on well-known latency