News Brief: Teen Pregnancy, and Sedentary Time and Disability

Data collected through NCHS’ National Vital Statistics System (NVSS) and National Health and Nutrition Examination Survey (NHANES) were used as the foundation for two important studies released this year that have attracted significant national media attention.

Teen Pregnancy and MTV

In January, the National Bureau of Economic Research released its paper, “Media Influences on Social Outcomes: The Impact of MTV’s 16 and Pregnant on Teen Childbearing.” The authors explored the influence of reality TV shows that follow pregnant teenagers through pregnancy, birth, and early motherhood on teen childbearing outcomes. The authors found that “… 16 and Pregnant … ultimately led to a 5.7 percent reduction in teen births in the 18 months following its introduction. This accounts for around one-third of the overall decline in teen births in the United States during that period.”

Using Vital Statistics Natality microdata to measure changes in teen birth rates, authors Melissa S. Kearney and Phillip B. Levine examined birth data from 2006 through 2011 to identify teen births that were conceived during that period. They also used data from Google Trends and Twitter to document changes in searches and tweets resulting from the show, and Nielsen ratings data to capture geographic variation in viewership. The authors cited the following benefits in using Natality microdata:

• Universal nature and large sample size of several hundred thousand teen births per year
• Ability to identify the exact age of the mother for every birth
• County identifiers, which allowed for the aggregation of births by occurrence in each Designated Market Area (DMA)
• Ability to approximate the month of conception in the data
• Ability to link timing of exposure to the show to the timing of the activities that led to a subsequent birth

The study and its results were the focus of articles in The New York Times, Los Angeles Times, Time magazine, Slate.com, TheAtlantic.com, CNN, and National Public Radio.

Sitting and Disability

In February, the Journal of Physical Activity and Health website added the study, “Sedentary Time in U.S. Older Adults Associated With Disability in Activities of Daily Living Independent of Physical Activity.” The study, led by lead author Dr. Dorothy Dunlop, examined whether time spent in sedentary behavior, such as sitting, is related to disability in activities of daily living (ADL), like simply moving around the home or apartment, independent of time spent in moderate-vigorous activity in older adults. The study found a strong relationship between sedentary time and the presence of ADL disability among older adults, regardless of how much time the subjects spent in other, more physically vigorous activities.

For their study, the authors analyzed data from the 2003–2004 and 2005–2006 NHANES cycles. Their final sample included 2,286 persons aged 60 and over. NHANES collected disability task information on ADL limitations from the participants in order to gauge their ability to carry out self-care tasks at the personal level (e.g., dressing). The participants’ physical activity was monitored using the ActiGraph AM–7164 accelerometer. The study found that the presence of ADL disability is related to greater daily hours and a greater daily percentage of time being sedentary. In fact, the study found that the odds of ADL disability increased by approximately 50% for each additional sedentary hour per day.

As the authors note, the study contributes substantially to the growing body of literature identifying sedentary behavior as a “separate disability risk factor” and not simply a “synonym for inadequate physical activity.” They conclude that “the strong demonstrated relationship between ADL disability and sedentary behavior suggests the importance of considering clinical, policy, and programmatic strategies to reduce sedentary behavior among older adults, particularly those with disabilities.”

Media coverage of the study included articles in the Los Angeles Times, Reuters news service, Canada’s CBC, and GMA News in the Philippines.