We performed a screening in primary care among apparently healthy individuals, to detect new MetS cases. Participants were only advised to contact their primary care center for the results of the screening. Upon contacting they were expected to receive usual care according to existing guidelines; no specific intervention was designed. More than half of the participants detected with MetS at screening no longer fulfilled the metabolic syndrome criteria three years later. The presence of more than three MetS components and a higher waist circumference, glucose level and systolic blood pressure were independently associated with a lower chance of remission.
Several studies have assessed the remission of MetS, all after an intervention. These interventions include diet (remission rate 21-61 %) [16–18], exercise programs (remission rate 42-58 %) [19, 20], combinations of both (remission rate 67 %) , bariatric surgery (remission rate up to 95 %) [22–24] and medication such as metformin, fenofibrate and orlistat (remission rate 23-44 %) [25, 26]. However, data about remission of the MetS without predefined intervention unless the advice to contact the primary care center are scarce. Two randomized controlled trials reported remission rates for their control groups of 9 and 18 % [26, 27]. Our higher remission rate might be explained by the intensity of our usual care, which was presumably higher than control group care as described by Orchard et al. and Bo et al. In these studies participants received lifestyle recommendations once, while the majority of our participants was seen several times by the practice nurse. The remission rate of 52 % observed in a prospective study more closely resembled our remission rate, which could be explained by an intervention more in agreement with our usual care . However the follow-up period was only six months; it is uncertain what would have happened after this relatively short intervention period.
In our study, not only individuals with diabetes or cardiovascular disease were excluded. Individuals were only eligible for screening if they were not previously diagnosed with hypertension or dyslipidemia and did not use antihypertensive, blood glucose lowering or cholesterol lowering medication: they were apparently healthy. The shock of suddenly being diagnosed with several risk factors might have been an extra impulse to change lifestyle, which might have contributed to the high remission rate. Two studies compared baseline characteristics between participants who did and did not achieve a remission [17, 19]. As in our study, the participants who did not achieve a remission had worse baseline values than the participants who did achieve a remission. This might be explained by the fact that achieving a remission is more difficult for participants with higher risk factor levels. Baseline HDL cholesterol level was not associated with remission, in contrast to baseline levels of glucose, waist circumference and systolic blood pressure, where lower baseline levels were associated with a higher chance of remission. HDL dysfunction could be an underlying reason for the absence of an association between baseline HDL cholesterol level and remission. Dysfunctional HDL particles lose their anti-inflammatory and atheroprotective properties. This condition is closely linked to obesity and to inflammation and might be more prevalent among people with high HDL concentrations. In Western populations, individuals with glucose intolerance or those at risk for cardiometabolic disease – people with MetS – could be affected by impaired function of HDL [29, 30].
Study limitations and strengths
This is the first study assessing remission of MetS after screening among apparently healthy people, without a predefined intervention program. The follow-up period of three years provides us with intermediate-term results. A shorter follow-up period might give too optimistic remission rates, because treatment effects and lifestyle changes tend to level off over time. Both socio-economic and demographic, biochemical and clinical variables were taken into account, as well as lifestyle factors. Our data on the prescription of cardiovascular medication were based on prescription according to the electronic medical record of the primary care physician. Actual use of the prescribed medication might be lower, since medication compliance, especially in primary prevention, is not optimal [31–33].
According to the NCEP ATP III criteria, when a patient is on drug treatment for a specific MetS component (antihypertensive drug treatment, blood glucose lowering treatment or treatment with a fibrate or nicotinic acid for a reduced HDL cholesterol or an increased triglyceride level) this component should be regarded as present, irrespective of the actual level of the component . This means that for example the blood pressure component will be regarded as positive as long as someone is on antihypertensive drug treatment, despite perfect blood pressure levels and thereby a reduced cardiovascular risk. Therefore, to gain insight into the actual reduction in cardiovascular risk achieved by remission, we chose not to take drug treatment for a specific MetS component into our definition of remission. In fact, the definition of the MetS provides a good screening tool to detect people with a high cardiovascular risk, but the current NCEP ATP III definition is less suitable for evaluating the effect of an intervention on changes in risk. If we had taken prescription of medication for a specific MetS component into account in our definition our remission rate would have been 49.0 %.
The overall response rate was good, although a substantial amount of the responders indicated not to be interested in participating in follow-up. This resulted in a relatively small study population. One might assume that people willing to participate were the more motivated patients, leading to potential bias for the generalization of the results. Indeed the participants more often entered a follow-up regimen after screening than the non-participants and non-responders. Whether their higher motivation also has led to a higher remission rate is questionable. However, we have to take into account this potential bias in interpreting the results. Especially younger people were less interested in follow-up measurements. At the initial screening, it were also the younger subgroups in which an invitation reminder was necessary to get a sufficient response. Apparently first it takes more effort to involve younger people in screening, and then we gain less insight into the impact of the screening for their cardiovascular health. It would be interesting to know the remission rate among the younger non-participants, since half of the people detected with the MetS were younger than 50 years . Age, however, was not significantly associated with achieving a remission in multivariable analysis.