A nonparametric methodological analysis of rest-activity rhythm in type 2 diabetes

Abstract

The purpose of this study was to analyze the rest-activity rhythm of type 2 diabetics mellitus (T2DM) and compare it to healthy controls using the nonparametric analytic approach. Twenty-one diabetics and 21 healthy subjects matched for gender and age were recruited to participate in the study. Data were analyzed using the Independent t-test, Mann-Whitney U test, and Spearmans correlation. T2DM subjects demonstrate lower interdaily stability (IS) (p=.03), higher intradaily variability (p=.046) and lower rhythm amplitude (p=.02) when compared to healthy controls. Also, there was a positive correlation between IS and most active 10 hr (M10) in the average of 24 hours pattern (r =.44; p=.046) in the diabetes group and a negative correlation between IV and M10 in the healthy group (r =-.57; p=.007). These data together suggest that T2DM exhibits a dysfunction in the rest-activity rhythm due to alterations in the circadian function as well as in the homeostatic capacity to maintain sleep; mainly characterized by less consistency across days of the daily circadian signal, higher rhythm fragmentation and lower rhythm amplitude. Future approaches may be developed considering the influence of circadian glucose variations throughout the day on the coupling of the rest-activity rhythm to zeitgeber and rhythm fragmentation.

Keywords: Circadian Rhythm; Diabetes Mellitus, Type 2; Sleep Wake Disorders.

Figure 1

Distribution of PSQI by semester. A score of more than 5 in Pittsburgh Sleep Quality Index (PSQI) define bad sleepers.

Figure 2

Actograms showing activity data (vertical black bars) divided into light phase (daytime, from 6:00 a.m. to 5:45 p.m., beige horizontal bar on top) and dark phase (night time, from 5:45 p.m. to 6:00 a.m., gray horizontal bar on center top). Yellow lines represent the variation in light throughout the day (24h period). Horizontal red bar represents when individuals were awake, and blue area indicates sleep period, with the lighter blue area indicating rest, and dark blue arrow head representing when subjects pressed a button on Actiwatch 2 to mark when they went to bed and when they woke up in the morning. Graph (A) illustrates a healthy subject; (B) a diabetic subject showing high instability between days, (C) a diabetic subject showing low rhythm amplitude, and (D) a diabetic subject showing high fragmentation.

Figure 3

Representation of the raw activity data (panels on the left) indicating the activity level (vertical black bars) throughout two consecutive days and double plots of the average 24-h activity level on solid line (panels on the right) of (A) a healthy subject; and (B and C) diabetic subjects both showing low rhythm amplitude, and high fragmentation.

Figure 4

(A) mean±SD light exposure (Lux multiplied by minute); (B) mean±SD average of all valid light (Lux) from the start time to the end time of active interval according to group. There were no significant differences between groups.