Next-gen data sources in life underwriting
Novel attributes to segment mortality risk
Sleep duration, resting heart rate, and grip strength
Woman Checking Smartwatch In Office checking resting heart rate
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    This paper is the second in our series examining the potential of third-party data sources to enhance life insurance underwriting.

    Background and objective

    This publication is a continuation of the collaboration between Klarity, a UK-based health data analytics firm, and Munich Re Life US to analyze the UK Biobank data.1 While the first whitepaper in this series examined activity data attributes in the Biobank dataset, this second paper shifts the focus to other novel variables in the dataset that are not typically considered in life insurance underwriting but provide evidence of protective value. We found evidence that resting heart rate, sleep duration, and grip strength are effective in stratifying mortality risk in a simulated insurable population. 

    This study examines the UK Biobank data to accomplish the following objectives: 

    • Compare findings to previous Munich Re studies on resting heart rate (RHR) and sleep duration for mortality risk segmentation. 

    • Assess a different dimension of health not typically used in underwriting, muscular strength, by studying the relationship between dominant hand grip strength and mortality risk.  

    Data and extrapolation to life insurance

    Like the earlier publications in this series, our analysis in this study focuses on the UK Biobank data that Klarity extracted. Variables relevant to this study include: 

    • Demographic information: age, gender, income, index of multiple deprivation (IMD, a UK measurement of poverty and access to services within a small geographic area2)  
    • Physical measurements/vitals: weight, height, waist circumference, hip circumference, BMI, blood pressure, resting heart rate 
    • Self-disclosed lifestyle attributes: smoking, alcohol use, sleep  

    Note that some variables, such as grip strength, were recorded in a well-controlled setting that may not be easily replicable in a life insurance underwriting setting. Also, the Biobank study participants were not underwritten for life insurance, so any anti-selection associated with applying for life insurance was not relevant in this setting.

    Like the previous studies, the analysis and results discussed onwards are based on the filtered “insurable” block of individuals, unless stated otherwise. 

    Classic actuarial methodology 

    We performed a classical actuarial actual-to-expected (A/E) mortality analysis on both the overall and “insurable” datasets. The expected mortality basis shown in the graphs below uses the UK National Life Tables, which are split by age, gender, and calendar year, without any mortality improvement. The overall A/E using the UK National Life Tables basis is 48%, indicating the mortality for this dataset is about half of the UK general population level. The A/E is 23% for the insurable dataset. 

    Overall results  

    Sleep is widely recognized as vital to physical and mental health through decades of medical and scientific research, and sufficient sleep protects against cardiovascular disease and diabetes.3 Biobank individuals self-disclosed typical hours of sleep and this information is available for over 99% of the insurable dataset. Nearly 90% of the simulated insurable population disclosed an average of six to eight hours of sleep per night, and the median daily sleep duration is seven hours. The lowest mortality risk is also at seven hours of sleep, which aligns with the American Academy of Sleep Medicine’s recommendation that adults obtain at least seven hours of sleep each night.4 We see a J-shaped pattern in the relative A/E mortality curve in Figure 1, and relative mortality for the group that sleeps up to five hours a night is elevated. Our findings align with previous Munich Re analysis on the effectiveness of daily sleep duration in segmenting mortality risk of a U.S. insured population.5
    Seven hours of sleep per night is associated with the lowest mortality risk, while five or fewer hours sharply increases mortality by 50%, underscoring the critical importance of sufficient sleep.  

    We consider resting heart rate (RHR) due to its link to cardiovascular health, a critical determinant of overall mortality. Resting heart rate is measured as part of the health assessment of Biobank study participants, and available for 92% of the “insurable” pool. The average resting heart rate among study individuals ranges from 30 to 174 bpm, with 81% of individuals in the normal RHR range of 60 to 100 bpm. According to the American Heart Association, a lower resting heart rate can indicate better heart function and cardiovascular fitness, where a physically active person could have a RHR of 40 bpm.6

    Figure 2 confirms that relative A/E mortality risk increases as resting heart rate increases. This is in contrast to a previous Munich Re study on heart rate and mortality , where we observed the classic J-shape curve in relative A/E mortality over the same resting heart rate groups.7 This difference may be due to the presence of more physically active individuals in the lowest heart rate group in our study. The lowest RHR group has the highest average daily step count and minutes of moderate/vigorous activity compared to the other heart rate groups. 

    Lower resting heart rates (RHR) correspond to reduced mortality risk. Notably, those in the lowest RHR group also have the highest average daily activity levels. 

    A resting heart rate of 80-89 bpm has nearly 50% higher relative mortality risk relative to a resting heart rate of 60-69 bpm. 
    Dominant hand grip strength (GS) is a measure of muscular strength, a dimension of health not considered in life insurance underwriting. Medical research suggests that grip strength is inversely related to mortality risk in adults.8 We use the maximum of an individual’s left and right-hand grip strength to obtain their dominant hand grip strength for the analysis below, and this metric is available for over 99% of the “insurable” pool. We find that for both men and women, mortality improves as GS increases (Figure 3). Note that we removed the relative mortality data points in the highest GS bucket for females due to lack of credibility at those extremes. Still, we observe that this metric differs significantly between men and women; females have a median dominant hand grip strength of 26 kg, whereas males have a median dominant hand grip strength of 42 kg. 
    Figures 4a and 4b show how GS distribution changes with age. Note that we split out the analysis of grip strength by gender due to the difference between males and females noted above, and we exclude individuals under the age of 40 and over the age of 70 due to a lack of data. Across gender, the oldest age range, 60-69, contain the highest proportion of individuals with low GS.
    From Figures 5a and 5b, we see that there is a strong relationship between GS and mortality across all age groups for both men and women. Poor GS is associated with an elevated mortality risk, and we find that the lowest GS category is associated with a mortality risk 1.5-2 times as high as the highest GS category, irrespective of age group and gender. Grip strength is an indicator of overall strength, and it can be linked to physical function and ability to perform the activities of daily living, such as bathing and eating. For the oldest age group in particular, the increased mortality risk due to low GS may be linked to difficulty in performing the activities of daily living. For this reason, GS can be a useful addition to the traditional underwriting toolkit for mature ages, where frailty may be a concern. 
    Grip strength is an indicator of overall physical strength and health and can effectively segment mortality risk across age and gender. 

    Conclusion 

    We confirm that sleep duration and resting heart rate are significant predictors of mortality, consistent with findings from past Munich Re Life US studies. Optimal sleep duration of seven hours is associated with the lowest mortality risk, while shorter sleep durations, particularly five or fewer hours, show a sharp increase in mortality risk. Resting heart rate analysis reveals that lower heart rates, often indicative of better cardiovascular fitness, correspond to reduced mortality risk. In addition, we find compelling evidence that low grip strength is indicative of adverse mortality for older age groups.

    However, it is important to note that some attributes, such as grip strength, require controlled conditions for accurate measurement, making their widespread use in life insurance underwriting more challenging. Even so, these findings highlight the potential for carriers to enhance their underwriting processes by incorporating such novel measures. On the other hand, resting heart rate and sleep duration are often recorded by wearable devices, enabling easier and more scalable implementation in a life insurance context. The increasing prevalence of wearable technology provides an opportunity for carriers to access real-time, continuous data on these attributes, further enhancing their predictive power for mortality risk.  

    References

    1This research has been conducted using the UK Biobank Resource under Application Number 88308. 2Index of Multiple Deprivation, Consumer Data Research Centre, 2024.  3How sleep affects human health, explained, UChicago News. 4Seven or more hours of sleep per night: A health necessity for adults, American Academy of Sleep Science, 2015.   5Sleep and mortality: Analyzing the effectiveness of daily sleep duration in stratifying mortality risk, Munich Re Life US, June 2020. 6Target Heart Rates Chart, American Heart Association, August 2024.   7Heart rate and mortality, Munich Re Life US, January 2021.   8Grip Strength: An Indispensable Biomarker For Older Adults, Clinical Interventions in Aging, 14, 1681, October 2019. 
    Contact
    Angela Gong
    Angela Gong
    Staff Data Scientist, Integrated Analytics
    Munich Re North America Life
    Murali Niverthi
    Murali Niverthi, PhD
    Director & Actuary, Underwriting Risk Assessment & Research
    Munich Re Life US

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