Flu More Dangerous for Some

Influenza linked to personal factors such as age and other medical conditions

(RxWiki News) The flu is a very common illness that affects all different types of people. But it may be more dangerous for some.

A recent study found that influenza-related deaths were influenced by age, sex and other medical conditions.

The researchers concluded that all these factors should be considered when deciding on the best route of treatment.

"Ask your doctor for a flu shot."

The lead author of this study was Edward Goldstein, MD, from the Department of Epidemiology of the Center for Communicable Disease Dynamics at the Harvard School of Public Health in Boston, Massachusetts.

The study used data on weekly death rates from 1997 to 2007 from the US National Center for Health Statistics. The researchers divided the data up according to week of death, age, sex and main cause of death.

Age was split up into five groups: 1) children under the age of 18, 2) young adults between 18 and 49 years old, 3) adults between the ages of 50 and 64, 4) seniors between the ages of 65 and 74 and 5) seniors 75 years and older.

The researchers considered data on all influenza-related deaths during the study period, as well as data on influenza-related deaths due to a variety of underlying conditions: all circulatory diseases, heart disease, cerebrovascular disease (affects blood vessels in the brain), heart attack, all respiratory causes, lower respiratory disease, pneumonia and influenza, cancer, diabetes, kidney disease, chronic liver disease, central nervous system disease, Alzheimer's disease, blood poisoning and unintentional injuries.

The study period of 1997 to 2007 included 10 influenza seasons. One flu season is from October of a given year until May of the next year.

The findings showed that the average influenza-related all-cause death rate over the whole study period was 11.78 deaths per 100,000 people per year.

The researchers found that the death rates increased significantly with age.

For the 75 and older group, the average yearly influenza-related death rate was 141.15 deaths per 100,000 people. Among 65- to 74-year-olds, the average annual death rate decreased to only 26.37 deaths per 100,000 people.

The researchers discovered that the average yearly death rate decreased to 7.18 deaths per 100,000 people for the adults between 50 and 64. And in the 18 to 49 age group, the death rate decreased to 1.03 deaths per 100,000 people.

Lastly, the average annual influenza-related all-cause death rate for children was 0.41 deaths per 100,000 people.

The findings showed that the highest death rates for the people in the 50 to 64, 65 to 74 and 75 and older age groups occurred in the late 1990s. For children, the 2003 to 2004 and 2006 to 2007 seasons saw the highest death rates.

It was also found that men in the 50 to 64 and 65 to 74 age groups had higher rates of all-cause deaths than women in the same age groups.

Men also had higher death rates than women in the 50 to 64 age group due to heart disease, in the 65 to 74 age group due to respiratory system disease, in the 65 to 74 and 75 and older age groups due to chronic lower respiratory disease, in the 50 to 64 and 65 to 74 age groups due to heart attack and in the 75 and older age group due to kidney disease.

The researchers discovered that women in the 75 and older age group had a higher influenza-related death rate due to Alzheimer's disease than men in the same age group. In addition, more men and women in the 75 and older age group died from underlying pneumonia and influenza than the men and women in the 50 to 64 and 65 to 74 age groups.

The findings also showed that female children represented the lowest number of influenza-related deaths in the study. Overall, men had higher death rates for all causes.

The researchers determined that the biggest difference between men and women was the rate of heart attacks, with men ages 50 to 64 having 2.95 times the number of deaths than women in the same age group. And for men ages 65 to 71, the death rate due to heart attacks was 1.71 times as much as the women in that age group.

The researchers suggested that doctors should take a patient's age, sex and underlying health conditions into consideration when determining the need for influenza vaccinations and treatment strategies.

The authors noted a few limitations of their study.

First, season-specific death rates may not be as reliable as the average yearly estimates. Second, there was a lack of data for the months not included in each influenza season, so yearly death rates may have been underestimated. Third, the data may not have accounted for influenza-related death rates due to a cause not considered in this study, such as neurological disorders.

This study was published online on November 4 in the American Journal of Epidemiology.

The National Institute of General Medical Sciences, the US National Institutes of Health and the National Institutes of Health provided funding.

Review Date: 
November 8, 2013