title: Absence of a seasonal variation in myocardial infarction onset in a region without temperature extremes.
abstract: 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.
authors.affiliation: Department of Internal Medicine, 802 Army General Hospital, Kaohsiung City, Taiwan, ROC.
authors.forename: C S
authors.initials: CS
authors.lastname: Ku
authors.forename: C Y
authors.initials: CY
authors.lastname: Yang
authors.forename: W J
authors.initials: WJ
authors.lastname: Lee
authors.forename: H T
authors.initials: HT
authors.lastname: Chiang
authors.forename: C P
authors.initials: CP
authors.lastname: Liu
authors.forename: S L
authors.initials: SL
authors.lastname: Lin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D002940:Circadian Rhythm; D002980:Climate; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000453:epidemiology / Q000209:etiology*; D012307:Risk Factors; D012621:Seasons; D013624:Taiwan / Q000453:epidemiology; D013696:Temperature