Question number 24-26 based on the passage below.

    Vitamin D deficiency is traditionally associated with bone and muscle weakness, but in recent years a number of studies have shown that low levels of the vitamin may predispose the body to high blood pressure, congestive heart failure, and chronic blood vessel inflammation (associated with hardening of the arteries). It also alters hormone levels to increase insulin resistance, which raises the risk of diabetes. In a review article published in the Journal of the American College of Cardiology, researchers surveyed recent studies on the link between vitamin D deficiency and heart disease to come up with practical advice on screening and treatment. They concluded that vitamin D deficiency is much more common than previously thought, affecting up to half of adults and apparently healthy children in the U.S. Researchers say higher rates of vitamin D deficiency may be due in part to people spending more time indoors and efforts to minimize sun exposure through the use of sunscreens. Sunscreen with a sun protection factor (SPF) of 15 blocks approximately 99% of vitamin D synthesis by the skin. "We are outside less than we used be, and older adults and people who are overweight or obese are less efficient at making vitamin D in response to sunlight," says O'Keefe. "A little bit of sunshine is a good thing, but the use of sunscreen to guard against skin cancer is important if you plan to be outside for more than 15 to 30 minutes of intense sunlight exposure."

How does the first sentence relate to the other sentence in the passage?