What is the fine-grained topic of the following text: A data analysis of samples tested of individuals in the age group of 21 to 65 years from October 2017 to March 2018 showed insufficient Vitamin D presence, with the age bracket of 21-35 years having maximum insufficiency of Vitamin D.
As per the data, around 55 percent of respondents fall under the age bracket of 20-29 years, followed by 30-39 years (26 percent), 40-49 years (16 percent), 50-60 years (2 percent) and 60-80 years (approximately 1 percent). Only return the topic.
Vitamin D insufficiency in different age groups based on data analysis.