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Title: Contribution of physical activity to the increased risk of type-2 diabetes in UK South Asians compared to Europeans
Author: Afaq, Saima
ISNI:       0000 0004 8499 3862
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Background: South Asians have ~3 times excess risk of T2D and related metabolic disturbances compared to Europeans. The known dietary, adiposity and genetic risk factors do not explain this excess risk of T2D in South Asians compared to Europeans. Contribution of physical activity to the increased T2D risk in South Asians remains undetermined. Methods: I determined the accuracy of three physical activity accelerometers amongst South Asians and Europeans. I estimated physical activity levels amongst UK South Asian and European men and women, using accelerometers, and investigated the association of physical activity with T2D, insulin resistance and related glycaemic disturbances by using univariate and multivariate analyses. Results: Energy expenditure Measured by the three accelerometers, in all the positions evaluated, was lower compared to Actual energy expenditure. Difference between Measured and Actual energy expenditure was smallest for the Actigraph GT3X+ in the ankle position compared to all other device-position combinations, amongst both South Asians and Europeans. Total physical activity, as determined by Actigraph GT3X+, was ~31% lower amongst South Asians compared to Europeans (P=0.01). After adjusting for age, sex and adiposity, an increase in physical activity was associated with reduced risk of T2D, insulin resistance and associated glycaemic disturbances (all P < 0.05). Incidence of T2D was 13.4% amongst South Asians and 4.6% amongst Europeans in the LOLIPOP cohort over mean 9 years' follow-up (P < 0.001). The age, sex and adiposity adjusted relative risk of T2D reduced from 3.3 (95% CI: 2.9-3.7, P=1.1 x 10-75) to 2.3 (95% CI: 2.0-2.7, P=4.5 x 10-35) after adjusting for total physical activity levels. The T2D population attributable risk (%) for achieving less than 600 MET.minutes per week was ~16% in South Asians and ~37% in Europeans. Conclusions: The results show that accelerometers are as effective in measuring physical activity in South Asians as they are in Europeans and Actigraph GT3X+ is the most accurate device for measuring physical activity in the two populations. My findings suggest the potential for increased physical activity to improve glucose metabolism and insulin resistance, which predict T2D risk, amongst South Asians and help reduce their excess risk of T2D and its related complications. However, an increase in physical activity alone is unlikely to bridge the 3-fold excess risk of T2D in South Asians compared to Europeans.
Supervisor: Chambers, John ; Kooner, Jaspal Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral