Diabetes and Obesity Trends in Tonga Over 40 Years

Abstract

Disparate population surveys of type 2 diabetes mellitus (T2DM) have been conducted in Tonga for 4 decades. This study standardizes these surveys to enable assessment of T2DM and obesity trends in Tongans aged 25 to 64 years over 1973-2012, and projects T2DM prevalence to 2020 based on demographic and population weight changes. Eight surveys were standardized to the nearest census to produce nationally representative estimates. Linear period trends and prevalence projections to 2020 were produced using random-effects meta-regression. Over 1973-2012, T2DM prevalence increased from 5.2% to 19.0% (1.9%/5 years) and obesity prevalence from 56.0% to 70.2% (2.7%/5 years). T2DM prevalence period projection to 2020 is 22.3%. Based on modeling using body mass index, T2DM prevalence in 2020 could have been 12.7% and 16.8% in 2020 had mean population weight been 1 to 4 kg lower than 2012 levels.

Trends in diabetes and obesity in Samoa over 35 years, 1978–2013

“…In Tonga, BMI increases explained 76% (men) and 73% (women) of T2DM prevalence increases over 1973–2012 [23]. BMI increases in Samoa, Fiji [22] and Tonga [23] have been attributed to changes in way of life, including a shift away from farming and fishing towards more sedentary occupations; and increased consumption of energy dense imported foods [24]. …”

High rate of diabetes in the Asia-Pacific Island: Possible role of rapid urbanization – A hospital based study

“…16 Similar observations were reported in other Pacific, African and Caribbean countries. 13,[17][18] In contrast, Lin et al 19 reported high prevalence of diabetes in both rural and urban areas in Pacific Tongans. This suggests adoption of new lifestyle which is closely associated with urbanisation in certain countries might not be applicable to some indigenous populations who are at high risk of diabetes irrespective of the rural-urban status.…”

Erroneous inflation of diabetes prevalence: Are there global implications?

“…It is apparent that in recent STEPS surveys in Fiji (2011), Samoa (2013) and Tonga (2012), the incorrect glucose cut‐off point was applied, and the T2DM prevalence reported were erroneously inflated to approximately double the actual T2DM prevalence had the correct glucose cut‐off point been applied (Table ; Figure ). When correct plasma cut‐off points are applied, changes in T2DM prevalence over the survey periods for each country are as follows: (i) Fiji, from 16.0 % to 15.6 % (−0.4 percentage points) over 2002–11 (instead of the reported +13.6 percentage points); (ii) Samoa from 21.5 % to 24.3 % (+2.8 percentage points) over 2002–13 (instead of +24.3 percentage points); and (iii) Tonga, from 22.4 % (including estimated all known T2DM) to 19.0 % (−3.4 percentage points) over 2004–12 (instead of +18 percentage points) …”

“…For these POC glucose meters, the whole blood glucose concentration is multiplied by 1.11 to express the glucose concentration as plasma equivalent, in accordance with recommendations from the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), first published in 2001 15 and repeated in 2005. 16 It is apparent that in recent STEPS surveys in Fiji (2011), 1,2 Samoa (2013) 3,4 and Tonga (2012), 5,6 the incorrect glucose cut-off point was applied, and the T2DM prevalence reported were erroneously inflated to approximately double the actual T2DM prevalence had the correct glucose cut-off point been applied ( 19.0 % (À3.4 percentage points) over 2004-12 (instead of +18 percentage points). 19 Some of the T2DM prevalence rates reported from other Pacific Island STEPS surveys 20 require further scrutiny where T2DM prevalence appears inordinately high and/or a considerable increase in prevalence is apparent compared with previous surveys.…”

“…16 It is apparent that in recent STEPS surveys in Fiji (2011), 1,2 Samoa (2013) 3,4 and Tonga (2012), 5,6 the incorrect glucose cut-off point was applied, and the T2DM prevalence reported were erroneously inflated to approximately double the actual T2DM prevalence had the correct glucose cut-off point been applied ( 19.0 % (À3.4 percentage points) over 2004-12 (instead of +18 percentage points). 19 Some of the T2DM prevalence rates reported from other Pacific Island STEPS surveys 20 require further scrutiny where T2DM prevalence appears inordinately high and/or a considerable increase in prevalence is apparent compared with previous surveys. For example, the eightfold increase in reported T2DM prevalence in Vanuatu from 2.8 % in 1998 to 21.2 % in 2011-12 21 appears to be unusually high in a country where obesity levels, the main T2DM risk factor, are relatively low for the region (19 %).…”