Association between objectively measured physical activity, chronic stress and leukocyte telomere length

BACKGROUND: Physical activity (PA) attenuates chronic stress and age-related and cardiovascular disease risks, whereby potentially slowing telomere shortening. We aimed to study the association between seven-day objectively measured habitual PA, chronic stress and leukocyte telomere length. METHODS: Study participants were African (n=96) and Caucasian (n=107) school teachers of the Sympathetic activity and Ambulatory Blood Pressure in Africans study. All lifestyle characteristics (including PA) were objectively measured. The general health questionnaire and serum cortisol were assessed as psychological and physical measures of chronic stress. Leukocyte telomere length was measured using the quantitative real-time polymerase chain reaction. RESULTS: Africans had significantly shorter telomeres (p<.001) and greater psychological distress (p=0.001) than Caucasians, whereas no group difference was seen for cortisol levels. Higher age [ß=-0.28 (-0.40, -0.16), p≤0.000], higher alcohol consumption [ß=-0.21 (-0.36, -0.08), p=0.003] and increased central obesity [ß=-0.17 (-0.30, -0.03), p=0.017] were all significantly associated with shorter telomeres. Habitual PA of different intensity was not significantly associated with markers of chronic stress or telomere length. However, more time spent with light intensity PA time was significantly and independently correlated with lower waist circumference (r=-0.21, p=0.004); in turn, greater waist circumference was significantly associated shorter telomeres [β=-0.17 (-0.30, -0.03), p=0.017]. CONCLUSION: Habitual PA of different intensity was not directly associated with markers of chronic stress and leukocyte telomere length in this biethnic cohort. However, our findings suggest that light intensity PA could contribute to lowered age-related disease risk and healthy ageing by facilitating maintenance of a normal waist circumference

The association between seven-day objectively measured habitual physical activity and 24 hr ambulatory blood pressure: the SABPA study

Few studies have examined objective physical activity in relation to 24 hour ambulatory blood pressure (BP). We aimed to assess the association of seven-day objectively measured habitual physical activity with ambulatory BP in a sample of African and Caucasian school teachers (n=216, age 49.7 yrs) from the Sympathetic Activity and Blood Pressure in Africans prospective cohort study. Hypertension (ambulatory systolic BP≥130 and / or Diastolic BP≥80 mmHg) was prevalent in 53.2% of the sample, particularly in black Africans. The hypertensive group spent significantly more awake time in sedentary activity (51.5 vs. 40.8 % of waking hours, p=0.001), as well as doing less light (34.1 vs. 38.9%, p=0.043) and moderate- (14.0 vs. 19.7%, p=0.032) intensity activities compared with normotensives, respectively. In covariate adjusted models, light intensity activity time was associated with lower 24-hr and day-time ambulatory systolic BP (β=-0.15 ,95% CI: -0.26, -0.05, p=0.004; β=-0.14, -0.24, -0.03, p=0.011) and diastolic BP (β=-0.14, -0.25, -0.03, p=0.015; β=-0.13 ,-0.24, -0.01, p=0.030), as well as resting Systolic BP (β=-0.13 ,-0.24, -0.01, p=0.028). Sedentary time was associated only with 24 hr Systolic BP (β=0.12; 0.01, 0.22), which was largely driven by night time recordings. Participants in the upper sedentary tertile were more likely to be “non-dippers” (odds ratio=2.11, 95% CI, 0.99, 4.46, p=0.052) compared with the lowest sedentary tertile. There were no associations between moderate to vigorous activity and BP. In conclusion, objectively assessed daily light physical activity was associated with ambulatory BP in a mixed ethnic sample