The finding could explain the low CHD mortality rates in some Mediterranean and Latin American countries where siestas are part of the culture.
The six-year cohort study included 23,681 people aged between 20 and 86 who had no history of CHD, stroke or cancer at baseline.
Participants were asked whether or not they took siestas, and if they did, the frequency and duration. Diet and physical activity levels were also considered.
During follow-up, 792 deaths were recorded, including 133 that were due to CHD.
People who took 30-minute siestas at least three times a week had a 37 per cent lower rate of CHD mortality than those who did not nap.
Additionally, people who took a midday nap once or twice a week had a 12 per cent reduction in CHD mortality, although this was non-significant.
Siestas seemed to benefit men the most, especially those working at the baseline. A lack of CHD deaths among working women meant a similar comparison could not made.
An afternoon nap might be a stress-reliever in a healthy individual, suggested the researchers. Stress is known to have short- and long-term effects on incidence and mortality from CHD.