{"id":759,"date":"2015-06-29T18:37:57","date_gmt":"2015-06-29T18:37:57","guid":{"rendered":"http:\/\/stg-blogs.bmj.com\/bmjebmspotlight\/?p=759"},"modified":"2017-08-21T11:46:44","modified_gmt":"2017-08-21T11:46:44","slug":"primary-care-corner-with-geoffrey-modest-md-atrial-fibrillation-incidence-in-framingham-study","status":"publish","type":"post","link":"https:\/\/stg-blogs.bmj.com\/bmjebmspotlight\/2015\/06\/29\/primary-care-corner-with-geoffrey-modest-md-atrial-fibrillation-incidence-in-framingham-study\/","title":{"rendered":"Primary Care Corner with Geoffrey Modest MD: Atrial fibrillation incidence in Framingham Study"},"content":{"rendered":"

By: Dr. Geoffrey Modest<\/strong><\/p>\n

The Lancet just published an article on\u00a0the trends of atrial fibrillation (afib)\u00a0over the past 50 years, based on the meticulous Framingham Study database\u00a0(see doi.org\/10.1016\/S0140-6736(14)61774-8<\/strong>). They looked at 9511 study participants from 1958-2007, assessing afib prevalence, incidence, risk factors and mortality over 10-year blocks, stratified by sex, with 202,417 person-years of observation. \u00a0Results:<\/p>\n

–There were 1544 cases of new-onset afib (821 men and 723 women)<\/p>\n

–Between the first and last 10-year groupings<\/p>\n

–The age-adjusted prevalence<\/em> of afib quadrupled from 20.4 to 96.2 per 1000 person-years in men, and from 13.7 to 49.4 cases per 1000 person-years in women\u00a0(p<0.001)<\/p>\n

–The age-adjusted incidence <\/em>of afib went\u00a0from 3.7 to 13.4 per 1000 person-years in men, and from 2.5 to 8.6 cases per 1000 person-years in women\u200b (p<0.001)<\/p>\n

–For EKG-diagnosed afib, found on routine exams\u00a0during the study,\u00a0the age-adjusted prevalence <\/em>per 1000 person-years increased from 12.6 to 25.7 in men (p=0.007)and 8.1 to 11.8 in women\u00a0(p=0.009) — of note, the pickup of afib over time decreased\u00a0for those\u00a0EKG-diagnosed during the routine exams\u00a0and increased in those\u00a0diagnosed\u00a0by reviewing\u00a0outside medical records (ie, more afib cases were diagnosed outside of the study and fewer during the study’s routine exams)<\/p>\n

–But, there was no significant change in the age-adjusted incidence <\/em>of afib\u00a0by EKGs in the routine exams\u00a0over time (increase was from 1.83 to 3.75 in men (p=0.06) and from 1.31 to 1.58 in women (p=0.23)<\/p>\n

–The prevalence of most risk factors changed over time\u00a0in those with new-onset afib,\u00a0as follows:<\/p>\n

–smoking decreased from 40.9% to 12.7%<\/p>\n

–moderate\/heavy alcohol decreased from 10.2% to 5.4%<\/p>\n

–BMI>30 increased from 27.3% to 35.4%<\/p>\n

–systolic BP>160mmHg decreased from 38.6% to 16.9%<\/p>\n

–hypertension treatment increased from 22.1% to 59.8%<\/p>\n

–diabetes increased from\u00a05.7% to 19.6%<\/p>\n

–prevalent heart failure decreased from 5.7% to 3.5%<\/p>\n

–significant heart murmur decreased from 20.0% to 8.1%<\/p>\n

–no significant change in prevalent MI<\/p>\n

–overall summary of the effects of these changes in risk factors: the population attributable risks for incident\u00a0afib\u00a0plummeted for systolic blood pressure (47.3 to -2.1), heart failure (7.8 to 1.4),\u00a0significant heart murmur (21.9 to 3.1)\u00a0and EKG-LVH (from 10.4 to 1.8), but increased\u00a0for BMI (12.0 to 16.9) and\u00a0diabetes (3.2 to 5.9). though systolic blood pressure decreased so dramatically, the attributable risk for treated hypertension (from 9.8 to 19.5) suggests that there is a residual\u00a0effect of hypertension even if treated, but much less so than untreated hypertension (and,presumably, hypertension prevention would be even better, eg by diet and exercise, ….)<\/p>\n

–over a 20-year period after the development of afib, there was a 74% decrease in stroke (p=0.001) and a 25.4% decrease in mortality (p=0.003)<\/p>\n

So, this study brings out some important points: many of the risk factors for afib are modifiable, and there have been some very impressive changes over the past 5 decades in several of them (especially the identification and treatment of hypertension, profound decreases in smoking, decreases in alcohol consumption), though these improvements have been somewhat\u00a0overcompensated by the worsening\u00a0in BMI and diabetes. The difference between prevalence and incidence are likely the result (for prevalence) of improved detection and the fact that people are living longer with afib\u00a0(impressive decreases in strokes and mortality). For example, I\u00a0do remember 20-30 years ago that it was not so clear that paroxysmal atrial fibrillation was as bad, and\u00a0in need to treatment, as permanent afib. Or that it was safe to use anticoagulants in older and somewhat frail\u00a0people. \u00a0Or that afib is as common as we now know it to be. The ascertainment of afib\u00a0by the screening EKGs during the study is probably the most consistent marker of real changes in incidence, and these were largely nonsignificant over time (in men it was pretty close to significant, but the point is that this confirms that the increase in BMI and diabetes makes up for the improvements in the other risk factors in the incidence of\u00a0afib\u00a0—\u00a0though, of course, there could be unidentified risk factors that play a role as well). And it is important to remember that the Framingham Study was based on white European immigrants.<\/p>\n","protected":false},"excerpt":{"rendered":"

Atrial fibrillation incidence in Framingham Study […]<\/p>\n

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