Absence of a seasonal variation in myocardial infarction onset in a region without temperature extremes

Cardiology. 1998 May;89(4):277-82. doi: 10.1159/000006800.


To evaluate whether the incidence of acute myocardial infarction (AMI) attack would have circadian, weekly and monthly variations in a subtropical area, 540 consecutive patients with AMI who were admitted to our coronary care units were analyzed. Six-hour intervals over 24 h, daily intervals in a week (7 days) and monthly intervals in a year (12 months) were studied, respectively. Results showed that there was a circadian variation in the onset of AMI with a morning (6 a.m. to noon) peak (34%, p < 0.01) but no secondary late evening (18-24 p.m.) peak. The incidence of AMI was significantly lower on Sundays (9%) than on the other weekdays (Monday through Saturday; p < 0.05). However, no monthly and seasonal variations in the incidence of AMI (no winter or summer peaks) were observed in this series. This study demonstrated a circadian variation in the onset of AMI attack with a predominant morning peak. The fewer AMI cases on Sundays compared to the other weekdays suggested that freedom from 'stress' or 'work-load' on Sundays might have an important impact on this low incidence of AMI. Unlike the large ranges in cold or hot weather found in temperate regions, the warm climate of a subtropical region does not affect the frequency of AMI.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Chi-Square Distribution
  • Circadian Rhythm*
  • Climate
  • Confidence Intervals
  • Female
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Myocardial Infarction / epidemiology
  • Myocardial Infarction / etiology*
  • Risk Factors
  • Seasons*
  • Taiwan / epidemiology
  • Temperature