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Scanning Sports Medicine

Latest Clinical Research Published by ACSM

Kiningham, Robert B. MD, MA, FACSM

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Current Sports Medicine Reports: April 2018 - Volume 17 - Issue 4 - p 107-108
doi: 10.1249/JSR.0000000000000476
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Association Between BMI Change and Cardiometabolic Risk in Retired Football Players

Professional football is a game played predominantly by very large men. While the body mass index (BMI) of these men can be deceptively high because of their large muscle mass, a playing weight BMI greater than 30 was found to double the risk of cardiovascular disease (CVD) mortality after retirement from the NFL (1). Trexler and colleagues (2) used data from the Health Survey of Retired NFL Players to examine if increases in BMI after retirement from professional football increased the risk of developing coronary heart disease (CHD), type 2 diabetes mellitus (DM), or high blood pressure (HBP).

All subjects were retired professional football players who responded to the Health Survey in 2001. The change in BMI was calculated from the players’ estimate of their playing weight and height, and their current weight and height. Covariates included age, years playing football, anabolic steroid use, smoking, alcohol intake, primary football position, and BMI at retirement.

The respondents’ average age was 53.6 yr, with an average of 24.4 yr since retirement. The multivariable model found that an increase in 5 BMI units increased the risk of developing CHD by 31%, DM by 69%, and HBP by 35%. BMI at the time of retirement also was significantly associated with the development of CHD, DM, and HBP, but to a lesser magnitude than change in BMI. To more fully explore the moderating effect of BMI at retirement on the impact of the change in BMI, the cohort was divided into two groups: BMI ≥ 30 (n = 848), and BMI <30 (n = 1214). In both groups, an increase in BMI of 5 was associated with a significant increased prevalence of DM (adjusted prevalence ratio [PR] 1.89 for nonobese, 1.63 for obese) and HBP (PR 1.41 for non-obese, 1.30 for obese). For CHD, the adjusted PR was 1.27 for non-obese (p = .07) and 1.39 for obese (P = 0.001).

The weakness of this study is that all the data were self-reported, much of it requiring recalling facts from several years previous. The questions also were very general. For example, the exercise question was “Are you currently exercising regularly?” The frequency, intensity, and mode of exercise could not be determined. The imprecision of these survey questions makes conclusions regarding the impact of the covariates speculative at best. However, a strong relationship was detected between an increase in BMI and health that is consistent with previous studies. The novel finding in this study, published in the April 2018 issue of Medicine & Science in Sports & Exercise® (MSSE) is that an increase in BMI increased the risk of CHD, DM, and HBP to a similar degree in both obese and nonobese players.

Bottom Line: A BMI increase after retirement significantly increases the risk of developing CHD, DM, and HBP in former NFL players regardless of their “playing weight” BMI.

Impact of Moderate-intensity and Vigorous-intensity Physical Activity on Mortality

The relative health benefits of moderate versus vigorous exercise have been the subject of debate among exercise specialists and public health organizations. The American College of Sports Medicine (ACSM) in their recommendations for exercise for adults focuses on achieving a minimum volume of exercise a week equivalent to 150 min of moderate exercise or a combination of moderate and vigorous exercise for less time (3). Whether more vigorous exercise has health benefits beyond an equivalent volume of moderate exercise is unclear. This large cohort study from Japan, also published in the April 2018 issue of MSSE, examined this question by classifying people into groups by both their relative overall physical activity and the proportion of their activity that is considered vigorous (4).

Data were taken from the Japan Public Health Center (JPHC)-based prospective study. This large population-based study surveyed adults ages 40 to 69 yr at the first survey (from 1990 to 1994) and then again at 5 and 10 yr. The 10-yr survey contained detailed questions regarding physical activity. The responses to the 10-yr follow-up study were used to classify people into four groups: inactive, active without vigorous physical activity (VPA), active with some VPA (<30% of total physical activity [PA]), and active with more VPA (≥30% of total PA). “Brisk walking” and “moderate intensity of activity such as playing golf or gardening” were classified as moderate physical activity (MPA) and assigned an energy cost of 3.0 METs. “Vigorous intensity activity such as jogging or playing tennis” were classified as VPA and assigned an energy cost of 6.0 METs. People were considered physically active if they totaled more than 450 MET·min−1·wk−1 and thereby met the recommendations for physical activity by the World Health Organization and ACSM.

The primary outcome variable was all-cause mortality determined by death certificates. Principal covariates were age, residential area, BMI, smoking, alcohol intake, diabetes, and hypertension. Subjects with a history of cancer or CVD, or with physical limitations, were excluded. Surveys from 99,447 people were received (response rate of 76%), of which 83,454 (38,598 men, 44,856 women) qualified for the study. Average age was 62 yr, with an average of 10.8-yr follow-up. A total of 84% of the men and 83.7% of the women were classified as “inactive.”

When compared with physically inactive men, physically active men with no VPA had a fully adjusted hazards ratio for all-cause mortality of 0.90, which did not quite reach statistical significance. However, physically active men with some VPA and more VPA had hazard ratio (HR) of 0.78 and 0.74, respectively, which were statistically significant. Physically active women in all three categories of VPA had statistically significant decreased all-mortality rates, with HR of 0.78 (no VPA), 0.66 (some VPA), and 0.64 (more VPA). When the physically active group with no VPA was used as the reference, both men and women in the more VPA had reduced all-cause mortality with fully adjusted HR of 0.81, although only the men’s reduction reached statistical significance.

The strength of this study is the very large cohort, high response rate, and complete follow-up. The major weakness is that the exercise data were based on self-reported estimates of physical activity, including the classification of physical activity as vigorous, moderate, or light. However, the conservative MET assignments for MPA and VPA may have offset the natural tendency of subjects to overestimate the frequency and intensity of their exercise. It also is important to note that this was an older group at baseline (average age, 62 yr). Vigorous and moderate exercise in a younger age group may have a different impact on cardiovascular risk factors and metabolic health than in this older cohort.

Bottom Line: Vigorous physical activity (defined as estimated MET level of ≥ 6.0) appears to enhance the protective effect of overall physical activity on all-cause mortality in men and women older than 60 yr.

References

1. Barron SL, Hein MJ, Lehma E, Gersic CM. Body mass index, playing position, race, and the cardiovascular mortality of retired professional football players. Am. J. Cardiol. 2012; 109:889–96.
2. Trexler ET, Smith-Ryan AE, DeFreese JD, et al. Associations between BMI change and cardiometabolic risk in retired football players. Med. Sci. Sports Exerc. 2018; 50:684–90.
3. Garber CE, Blissmer B, Deschenes MR, et al. American College of Sports Medicine Position Stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med. Sci. Sports Exerc. 2011; 43:1334–59.
4. Kikuchi HK, Lee I, Odgiri Y, et al. Impact of moderate intensity and vigorous-intensity physical activity on mortality. Med. Sci. Sports Exerc. 2018; 50:715–21.
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