# 6907
It is well established that death rates go up during the winter months, although the reasons behind these spikes in mortality are not entirely clear (or agreed upon). A few theories put forth include:
Colder temperatures, increased respiratory infections (including influenza & Pneumonia), over indulgence in food and alcohol, diminished activity levels, forgetting to take prescription medicines, and combined holiday stressors like shopping, running up debt, traveling, meal preparation, and the angst that comes from dysfunctional family gatherings . . . .
Nearly 15 years ago, a study looked at the rate of heart attacks in the United States, and found that Acute Myocardial Infarctions (AMIs) run as much 53% higher during the winter months than than during the summer.
Spencer FA, Goldberg RJ, Becker RC, Gore JM.
While cold weather combined with strenuous physical activity (like clearing snow from sidewalks) has often been blamed for this spike, even in balmy Southern California, studies have shown a 33% increase in heart attacks over the holidays (see below).
When Throughout the Year Is Coronary Death Most Likely to Occur?
A 12-Year Population-Based Analysis of More Than 220 000 Cases
Robert A. Kloner, MD, PhD; W. Kenneth Poole, PhD; Rebecca L. Perritt, MS
Increasingly – but perhaps not conclusively - influenza and other respiratory infections have been linked to this seasonal increase in heart attacks.
Last October, in Study: Influenza And Heart Attacks, we looked at research that appeared in the Journal of Infectious Diseases that suggested Influenza - and other acute respiratory infections - can act as a trigger for heart attacks.
Influenza Infection and Risk of Acute Myocardial Infarction in England and Wales: A CALIBER Self-Controlled Case Series Study
Charlotte Warren-Gash, Andrew C. Hayward1, Harry Hemingway2, Spiros Denaxas2, Sara L. Thomas3, Adam D. Timmis5, Heather Whitaker6 and Liam Smeeth4
The same issue carried an editorial called Increasing Evidence That Influenza Is a Trigger for Cardiovascular Disease.
In 2010, in CMAJ: Flu Vaccinations Reduce Heart Attack Risk we saw what would turn out to be a controversial study (see Vaccine/Heart Attack Study Questioned) that strongly suggested that those over the age of 40 who get a seasonal flu vaccine each year may reduce their risk of a heart attack by as much as 19%.
So the idea that heart attacks may be linked to influenza infection is hardly new.
As winter brings many other elements into the equation it has been difficult to isolate influenza as a major cause for the spike in AMIs during each winter.
Adding to our understanding of this issue, we have a study from the University of Iowa in the January issue of the journal of Epidemiology and Infection that links spikes in AMIs to influenza during the winter months, and also finds a similar spike in AMIs during the H1N1 pandemic wave of the fall of 2009.
Acute myocardial infarctions, strokes and influenza: seasonal and pandemic effects
E. D. FOSTER, J. E. CAVANAUGH, W. G. HAYNES, M. YANG, A. K. GERKE, F. TANG and P. M. POLGREEN
SUMMARY
The incidence of myocardial infarctions and influenza follow similar seasonal patterns. To determine if acute myocardial infarctions (AMIs) and ischaemic strokes are associated with influenza activity, we built time-series models using data from the Nationwide Inpatient Sample.
In these models, we used influenza activity to predict the incidence of AMI and ischaemic stroke. We fitted national models as well as models based on four geographical regions and five age groups.
Across all models, we found consistent significant associations between AMIs and influenza activity, but not between ischaemic strokes and influenza. Associations between influenza and AMI increased with age, were greatest in those aged >80 years, and were present in all geographical regions.
In addition, the natural experiment provided by the second wave of the influenza pandemic in 2009 provided further evidence of the relationship between influenza and AMI, because both series peaked in the same non-winter month.
The University of Iowa has a press release with more information, at the link below:
UI study suggests flu vaccine protects against heart attacks
Research focuses on older adults
Debra Venzke | 2013.02.04 | 07:02 AM
A new study from researchers at the University of Iowa suggests that the flu vaccine may provide protection against heart attacks in older adults, particularly those over age 80.
Scientists have long recognized that deaths due to influenza and deaths from other non-influenza-related diseases follow a similar seasonal pattern. This has lead researchers to suspect that acute infection caused by influenza may trigger events leading to heart attacks and strokes.
To determine if heart attacks and strokes are associated with influenza activity, the UI researchers built a set of time-series models using inpatient data from a national sample of more than 1,000 hospitals.
Across all models, the researchers found consistent significant associations between heart attacks and influenza activity. The study was published online Jan. 3 in the journal Epidemiology and Infection.
The question of just how much protection the current flu shot technology provides to elderly persons is the subject of considerable debate as well (see NFID: The Challenges Of Influenza In Older Adults excerpts below)
From a 5-page brief, published in 2011, called: Understanding the Challenges and Opportunities in Protecting Older Adults from Influenza:
Although the elderly generally see less protection from the flu vaccine, older individuals may still mount a robust immune response. In populations 65 and older, the brief points out that:
- Hospitalization rates for influenza and pneumonia are lower in community-dwelling adults who received the seasonal influenza vaccine.
- Immunization is associated with reduced hospitalization of older patients for cardiac, respiratory, and cerebrovascular diseases.
While the goal of vaccinating the younger population is to prevent infection, the authors point out that:
- . . . the goal in older adults is to prevent severe illness, including exacerbation of underlying conditions, hospitalization, and mortality.
In other words, even if the vaccine doesn’t always prevent infection in the elderly, studies suggest that the vaccine may blunt the seriousness of the illness in those over 65.
As I reported on Friday in CDC FluView Week 4:
Influenza-related hospitalizations continue to be heavily skewed towards those over 65, reaching an 116.1 per 100,000 population, accounting for more than half of all hospitalizations.
And we are seeing levels of P&I (Pneumonia & Influenza) related mortality – predominately among the elderly – at rates unseen in a decade.
Which makes getting the current flu vaccine – even if it is far less effective that we might desire - better than going into influenza season having no protection at all.
