Watching too much television and leading a sedentary lifestyle during early to mid-adulthood not only contributes to obesity, heart disease, and risk of type II diabetes — it can also affect cognitive function, according to new studies.

The findings were presented at the 2015 Alzheimer's Association International Conference (AAIC) held in Washington, D.C. by researchers from Northern California Institute for Research and Education in San Francisco, California.

The study involved over 3,200 adults from 18 to 30 years old, who were also part of a study called the Coronary Artery Risk Development in Young Adults (CARDIA).

For the study, researchers defined excessive TV viewing as staying in front of the screen for more than four hours per day. In addition, they defined physical inactivity as "activity below 300 Kcal per 50-minute session, three times weekly," as reported in Medical News Today.

For 25 years, researchers followed on the participants and assessed their levels of physical inactivity and TV viewing time.

Over the 25-year study period, 17 percent of participants were classified to have a "long-term pattern" of physical inactivity; 11% were viewing TV intensely; and 3% of them had both patterns.

At the end of the study period, the participants took a series of tests that looked into their cognitive function, which include processing speed and memory skills.

Analysis showed that those who watched too much TV and engaged in low physical activity were two times more likely to perform poorly during the cognitive function tests, compared to participants who had less amount of TV time and were physically active, according to Kristine Yaffe of University of California in San Francisco.

The results only suggest that early sedentary habits can have a great impact on a person's risk of developing dementia later in life.

Medical News Today reports that the 2008 Physical Activity Guidelines for Americans stated that adults from 18 to 64 years old should at least observe "moderate-intensity" physical activity for 150 minutes or vigorous-intensity workouts for 75 minutes every week.

However, the Centers for Disease Control and Prevention (CDC) reports that only one out of five adults follow the said guidelines.