Heart rate variability (HRV), the change in the time intervals between adjacent heartbeats, is an emergent property of interdependent regulatory systems that operates on different time scales to adapt to environmental and psychological challenges. Low age-adjusted HRV has been confirmed as a strong, independent predictor of future health problems in both healthy people and patients with a wide range of diseases that correlate with all-cause mortality. Twenty-four–hour HRV recordings are considered the gold standard and have greater predictive power on health risk than short-term recordings. However, it is not always practical or cost effective to obtain 24-hour HRV recordings, and short-term recordings have been widely used in research and clinical applications for many years. This article will report on the first in a series of research investigations on short-term HRV assessments. The first study examined the correlations between a 10-minute resting state, a 1-minute paced deep breathing protocol, response to handgrip, and 24-hour HRV measures in 28 healthy individuals. Based on the results of the initial study, the primary study examined the correlations between the 1-minute paced deep breathing assessment and 24-hour measures in a general population of 805 individuals. Overall, the findings from the studies suggested that the 1-minute paced deep breathing assessments were highly correlated with 24-hour measures of vagally mediated HRV and very-low-frequency power. The findings from this study suggest that the 1-minute paced deep breathing protocol is an ideal short-term assessment that can be used in a health risk screening context. When low values are observed, it is recommended that a 24-hour assessment be conducted.