Need help with a question pleases

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A

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Is this meant to say why dearth from CVD is decreasing or why CV health is decreasing because questions like usually ask why cardiovascular disease is increasing.
Is this a specific question? Because if it is you could say rates of smoking are decreasing as smoking increases blood pressure and contributes to plaque building up on artery walls, less people smoking may decrease the number of people with CVD.

For cancer
 
Advancing age is a risk factor for developing cancer, the current population has a significant proportion of those who getting older, this can increase the incidence of cancer.
Or you could talk about Diet, how less people are eating fruit and vegetables --> Less fibre --> increased risk of some cancers.
There are many more examples for this disease.