Metabolic Syndrome Risk Among Adults Living with Sickle Cell Disease

Background: The life span of individuals living with sickle cell disease (SCD) has increased considerably over the past three decades. Yet, as this group ages, new concerns emerge about their overall health profile – particularly with regard to cardiovascular disease (CVD), the primary cause of mortality in the United States. Metabolic syndrome (MetS) is a cluster of conditions that are associated with a 2-fold increase in CVD outcomes and a 1.5-fold increase in all-cause mortality. Little is known, however, about the prevalence of MetS risk factors among adults with SCD. As part of exploring the CVD profile of this population, we report findings from a pilot study that sought to evaluate MetS (typically defined as the presence of 3 or more risk factors).

Methods: 49 adults (ages 21-66 years; 72% female) completed demographic and health behavior surveys, health-related family and personal histories, anthropometric measurements, the Block 2005 nutritional assessment, and a comprehensive blood panel. In terms of SCD genotype, 63% of participants were diagnosed with homozygous sickle cell anemia and 37% were diagnosed with hemoglobin SC disease. Descriptive and inferential statistics were used to summarize and compare MetS components stratified in separate analyses by genotype and sex.

Results:  The most prevalent MetS risk factors observed in our study – large waist circumference and reduced HDL levels – affected 45% and 69% of the sample, respectively. Overall, 16% of participants met traditional criteria for MetS. Table 1 summarizes mean values and shows the gender-adjusted risk for MetS. Although 78% of the sample self-reported moderate to high physical activity, nearly half of participants were overweight and had dietary saturated fat intake levels that exceeded both the national average and US Dietary Guidelines (<10%). Participants with the SC phenotype were older, consumed more calories, and had higher BMI, waist circumference, and BP values compared to those with the SS phenotype. Overall, males had worse MetS risk profiles compared to women, but no statistically significant sex differences were observed with regard to components of MetS.

Conclusion: We report prevalence of MetS components, a surrogate of CVD risk, in a sample of adults living with SCD.  Despite high levels of self-reported physical activity, both increased waist circumference and reduced HDL levels were notably high in our sample.  These findings correspond with recent studies that indicate an upward trend in obesity and BMI among young adults with SCD.  They also suggest a need to prioritize weight management, aerobic exercise, and resistance training strategies that could decrease MetS risk, but are rarely considered for this population.

Table 1: Metabolic syndrome risk among adults living with SCD (N=49)

	Mean Value (SD)		Proportion at Risk*
	Male (n = 14)	Female (n = 35)	Male (n = 14)	Female (n = 35)
Age (years)	41.6 (10.76)	39.3 (12.86)	-	-
Waist circumference (cm)	96.53 (21.99)	90.75 (14.05)	42.9%	45.7%
Triglycerides (mg/dL)	114.21 (57.22)	83.36 (36.21)	21.4%	3.0%
HDL (mg/dL)	35.07 (9.51)	51.30 (20.31)	78.6%	69.7%
Systolic BP	115.79 (15.00)	108.59 (13.15)	21.4%	8.6%
Diastolic BP	69.11 (8.99)	62.17 (6.18)	0.0%	0.0%
Fasting Glucose (mg/dL)	86.50 (8.07)	80.91 (13.73)	0.0%	9.0%
Metabolic Syndrome	-	-	28.6%	8.6%

*"Risk" is defined as: waist circumference > 89cm (Females) and > 102cm (Males); triglyceride levels > 150mg/dL; HDL levels < 50mg/dL (Females) and < 40mg/dL (Males); systolic blood pressure > 130; diastolic blood pressure > 85; fasting glucose levels > 100mg/dL.