Madam
Thank you for drawing the letter of Ivy Shiue to our attention in relation to our papers on each of shopping(Reference Chang, Chen and Wahlqvist1) and cooking(Reference Chen, Lee and Chang2) and survival.
As your correspondent has noted, in the cooking paper we adjusted for shopping in conjunction with other possible confounders and found this made no difference to our findings about its association with survival (Table 4), even though cooking and shopping are associated with each other (Table 1). Also, in its own right, adjustment for shopping made no difference to the findings.
Like Shiue, we are aware of the link between hypertension and mortality, some of which is explained by covariates for which we have adjusted in our models, including age and a wide range of co-morbidities(Reference Chang, Chen and Wahlqvist1). Nevertheless, adjustments for the presence of hypertension itself in each of our reports, on shopping and on cooking and survival, make no difference to the findings.
We are confident that, insofar as the analyses allow, there are meaningful linkages between both shopping and cooking, independently of each other, on survival and that these are evident irrespective of the presence of hypertension.
