Does surfing the internet raise your blood pressure?
"American researchers discovered a link between internet use and high blood pressure [in teens]," The Independent reports. But the study did not actually find heavy internet use was associated with high blood pressure.
The study included 331 adolescents aged 14 to 17. They had their blood pressure measured and provided an estimate of the amount of time they spend on the internet each week. "Heavy" internet use was defined as two or more hours every day, while "light" internet use was less than two hours on less than four days a week.
The only statistically significant result was that heavy internet use was associated with slightly higher diastolic blood pressure (the lower of the two numbers) compared with light internet use. However, this was still within normal blood pressure levels.
Though the results of this study do not indicate that heavy internet use is associated with high blood pressure, it is generally advised that adolescents stay physically and socially active for a healthy mind and body.
Where did the story come from?
The study was carried out by researchers from Henry Ford Hospital, Wayne State University, and the University of Michigan. It was funded by the Henry Ford Hospital.
The study was published in the peer-reviewed Journal of School Nursing on an open access basis, so it is free to read online or download as a PDF.
The Independent's reporting of the study was inaccurate, telling readers that researchers found a "link between internet use and high blood pressure" – this was not the case.
The paper did quote one of the lead authors of the study, Andrea Cassidy-Bushrow, but did not make it clear that this was an opinion, rather than a fact backed up by the results of the study.
She is reported to have said: "It's important that young people take regular breaks from their computer or smartphone and engage in some form of physical activity. I recommend to parents they limit their children's time at home on the internet. I think two hours a day, five days a week, is a good rule of thumb."
There are currently no agreed guidelines on the amount of time children should spend on the internet. However, we do know excessive screen time has been linked to teenagers getting less sleep.
What kind of research was this?
This cross-sectional study aimed to assess the association between time spent on the internet and elevated blood pressure in a racially diverse sample of adolescents aged 14 to 17 in the US.
The researchers said children with elevated blood pressure are at an increased risk of developing high blood pressure (hypertension) as adults. Identifying the causal factors that contribute to this may be helpful in setting up primary prevention strategies for adult hypertension, they say.
They added that other studies linked internet use to many psychosocial factors, such as addiction, depression, anxiety and social isolation. In turn, these factors were associated with elevated blood pressure in adults.
This kind of study design examines the relationship between two factors in a defined population at a single point in time. This means it cannot show causality, as many other factors may be involved. It also cannot explain the long-term impact of internet exposure.
What did the research involve?
The researchers invited 1,837 adolescents aged 14 to 17 from the metropolitan city of Detroit in the US to participate in the study, identified through the Henry Ford Health System. In total, 335 adolescents agreed to take part, which meant attending a clinic on one occasion with a parent or guardian.
At the clinic, a trained interviewer took their blood pressure four times and then recorded the average reading from the last three recordings. From this, adolescents with high blood pressure were identified.
The adolescents then completed a questionnaire on how many days a week and the number of hours a day they used the internet. This included time spent on the internet using computers and devices such as smartphones.
Researchers also collected information on other factors (confounders) that could influence the link between internet use and high blood pressure, such as:
- body mass index (BMI)
- race
- smoking history
- physical activity
- socioeconomic status
- family history of hypertension
What were the basic results?
Results were drawn from a total of 331 adolescents. Their mean age was 16.4 and the average amount of internet time was 15.1 hours a week.
Overall, the mean number of hours a week spent on the internet was higher in adolescents with elevated blood pressure compared with those with normal blood pressure (18.0 hours versus 14.6 hours). However, this was not statistically significant.
Heavy internet users had the highest average diastolic blood pressure (the lower of the two numbers) compared with light internet users.
This was 3.4mmHg higher, but still within the normal range of diastolic blood pressure (65.0±7.8 versus 61.5±7.5). There was no association between systolic blood pressure (the higher of the two numbers) and internet use.
The study found no evidence that gender, race and family history of hypertension changed the association between elevated diastolic blood pressure and internet use in adolescents.
How did the researchers interpret the results?
The researchers concluded that, "Internet use and computer use are not necessarily the same activity, as individuals can be using the computer but not the internet (e.g. editing a document or playing a computer game). Furthermore, because the age range and time period of study vary across previous studies, and media use across time has changed, it is challenging to make inferences across studies."
They added that, "Future studies that specifically examine different internet activities (e.g. internet gaming and social media) and the device used to access the internet (e.g. desktop computer and smartphone) may be needed to fully understand what component of internet use is associated with increased BP."
Conclusion
This cross-sectional study looked for an association between time spent on the internet and elevated blood pressure in a group of adolescents in the US.
Overall, the results of this study did not find increased internet use was associated with hypertension in adolescents.
The only statistically significant result was that heavy internet use was associated with a slightly higher diastolic blood pressure compared with light internet use, but this was still within the normal range.
Although researchers say this is the first study to their knowledge that examines the association between internet use alone and elevated blood pressure, it has several limitations. These include:
- Blood pressure measurements were collected at a single point in time. This is not sufficient to diagnose hypertension, as blood pressure should be taken on separate occasions, and high blood pressure should be confirmed on continuous ambulatory monitoring or home blood pressure monitoring.
- Adolescents self-reported the number of days and hours spent on the internet in the past year. This may not be an accurate estimate, especially when they give this estimate in front of a parent or guardian, in addition to the potential for recall bias.
- The study did not measure adolescents' time doing a particular activity on the internet, such as school assignments compared with gaming.
Although the researchers accounted for most common confounding factors, there may be other factors that might have had an impact on the outcomes measured.
Teenagers' bodies and brains are still developing, so it is important that they get the minimum amount of physical activity:
- at least 60 minutes of physical activity every day – this should range from moderate activity, such as cycling and playground activities, to vigorous activity, such as running and tennis
- on three days a week, these activities should involve exercises that build strong muscles, such as push-ups, and exercises for strong bones, such as jumping and running
