In most countries for which data are available, the incidence of diagnosed diabetes rose from the 1990s to the mid-2000s, but has been stable or falling since, according to a new analysis. The authors of the study,* published in The BMJ, said they thought preventive strategies and public health education and awareness campaigns could have contributed to this trend, but commentators agreed that study limitations mean interpretation of the results is difficult and should be done with caution.
The research team, from Australia, the US and UK, conducted a systematic review of studies that had reported trends of diabetes incidence in adults from 1980 to 2017; the 47 included studies covered a total of 121 separate sex-specific or ethnicity-specific populations.
Their review found that in 1960-89, 36% (8/22) of the populations studied had increasing trends in incidence of diabetes, 55% (12/22) had stable trends, and 9% (2/22) had decreasing trends. In 1990-2005, diabetes incidence increased in 66% (33/50) of populations, was stable in 32% (16/50), and decreased in 2% (1/50). But in 2006-14, increasing trends were reported in only 33% (11/33) of populations, whereas 30% (10/33) and 36% (12/33) had stable or declining incidence, respectively.
The study authors noted some limitations of their study, such as their inability to source age- or sex-specific data on all populations; being unable to adjust for different methods of diabetes diagnosis or ascertain trends by different definitions of diabetes; most data sources reported only on clinically diagnosed diabetes and so were subject to influence from diagnostic behaviour and coding practices; and study type changed over time, with large administrative datasets becoming more common and cohort studies becoming less common over time. They also noted that there was little evidence from low- and middle-income countries where trends might be different.
They concluded: “This systematic review shows that in most countries for which data are available, the incidence of diagnosed diabetes was rising from the 1990s to the mid-2000s, but has been stable or falling since. Preventive strategies and public health education and awareness campaigns could have contributed to this recent trend. Data are limited in low- and middle-income countries where trends in diabetes incidence might be different. Improvement of the collection, availability, and analysis of incidence data will be important to effectively monitor the epidemic and guide prevention efforts into the future.
The authors of an accompanying editorial** added that – as is usual with systematic reviews – this study sought to answer a different question from that posed by the source studies, so caution is always required in interpreting its results. And, they added, falling or stalling incidence might reflect individuals’ increasing unwillingness to engage with health checks or screening, through life stresses or disinterest or because some people reject the possibility of being labelled as sick.
They pointed out that various factors are driving action to achieve remissions through effective weight management programmes for people with type 2 diabetes, and said: “If these programmes are provided for people with screen-detected prediabetes, incidence of type 2 diabetes will fall. While we all long for signs that diabetes is in retreat, this sensibly optimistic systematic review does not provide definitive evidence that true incidence is finally falling.”
* Magliano DJ, Islam RM, Barr ELM, et al. Trends in incidence of total or type 2 diabetes: systematic review. BMJ 2019; 366: l5003
** Lean M, McCombie L. Editorial: Trends in type 2 diabetes. BMJ 2019; 366: l5407