From the available data, it is unclear whether the higher frequency of stroke and high blood pressure among participants who napped might be due to more sleep apnoea (a disorder that causes daytime sleepiness and increased risk of stroke and high blood pressure). Short naps of less than 20-30 minutes are restorative, as opposed to long naps. The latter actually reflect an insufficient night's sleep due to a sleep disorder such as apnoea, phase delay, jet lag, shift work sleep disorders or periodic leg movements, among others. 

The role of napping should be individualised for each patient to assess its impact on night-time sleep. 

This is a good study involving a large number of people, although the conclusion should not be that it is naps that increase the risk of stroke and hypertension. There is evidence that frequent naps of more than 30 minutes are associated with some diseases, including cardiovascular disease. However, such naps are most likely a reflection of insufficient or poor quality night-time sleep. It is quite possible that the increased risk is due to what happens at night, and that the effect of naps is not sufficient to counteract it. 

The study has certain limitations, such as the fact that it is based on surveys that do not objectively capture sleep time and quality.  

If the study were to send a message, it would be that excessive naps should serve as a warning sign of insufficient night-time sleep.