Melatonin and cortisol profiles in late midlife and their association with age-related changes in cognition

Figures & data

Figure 1 Median circadian profile of salivary melatonin in cognitively impaired (dashed line) and cognitively high-functioning (solid line) participants.

Note: Values are expressed as median ± median absolute deviation.

Figure 2 Median circadian profile of salivary cortisol in cognitively impaired (dashed line) and cognitively high-functioning (solid line) participants.

Note: Values are expressed as median ± median absolute deviation.

Table 1 Distribution of sociodemographic and clinical variables in 50 cognitively high-functioning (group 1) and cognitively impaired (group 2) middle-aged men

	Group 1 (N=24)	Group 2 (N=26)	P-value
Age (years)	57.5±0.45	57.3±0.45	ns
Sex (% male)	100	100	ns
Ethnicity (% Caucasian)	100	100	ns
Years in education	13.96±2.46	12.5±2.12	0.03
BMI (kg/m^2)	27.1±4.45	27.06±3.71	ns
Waist circumference (cm)	95.78±25	96.38±26.5	ns
Blood pressure
Systolic	148±14	137±32	ns
Diastolic	89±8	83±24	ns
Alcohol drinking habit
Current (yes/no)	23/1	25/1	ns
Smoking habit, n (%)
Current	9 (41)	11 (42)	ns
Former	8 (29)	6 (23)	ns
Never	7 (30)	9 (35)	ns
BDI-II	2.48±3.24	3.32±4.31	ns
ESS	6.40±3.42	4.20±2.61	ns
Physical and psychiatric morbidity, n (%)
Hypercholesterolemia	8 (2)	3 (4)	ns
Hypertension	21 (5)	19 (5)	ns
Other current or former	0 (0)	15 (4)	ns
cardiovascular disease
Type 2 diabetes	0.5 (1)	0 (0)	ns
Asthma/COPD	1 (1)	2 (3)	ns
Arthritis	12 (3)	27 (7)	ns
Allergic illness	4 (4)	1 (1)	ns
Any current or former	18 (17)	11 (10)	ns
migraine or other
neurological disease
Any former malignity	0	0.5 (1)	ns
Any former depressive episode	2 (8)	12 (3)	ns

Notes: Data are mean ± standard error of the mean, or number and percentage. P-values are those from independent-samples t-tests (continuous variables) or χ² tests (categorical variables). P-values ≥0.05 were considered not significant.

Abbreviations: ns, not significant; BMI, body mass index; BDI-II, Beck Depression Inventory; ESS, Epworth Sleepiness Scale.

Table 2 The circadian parameters of salivary melatonin and cortisol in 24 cognitively high-functioning (group 1) and 26 cognitively impaired (group 2) middle-aged men

	Group 1 (N=24), estimate ± SE	Group 2 (N=26), estimate ± SE	P-value*
Median peak melatonin level (pg/mL) at 4 am	10.50±1.19	5.90±1.14	0.006
Mean 24-hour mean melatonin level (pg/mL)	4.80±0.70	4.81±0.76	ns
Mean AUC melatonin (h × μg/mL)	126.7±6.6	127.5±7.7	ns
Median peak level cortisol (μg/100 mL) at 8 am	0.16±0.03	0.12±0.02	ns
Mean 24-hour mean cortisol level (μg/100 mL)	0.11±0.01	0.12±0.01	ns
Mean AUC cortisol (h × μg/100 mL)	2.70±0.07	2.73±0.08	ns

Notes:

* Differences between groups were assessed by median regression (median) or independent-samples t-tests (24-hour mean and AUC). P-values ≥0.05 were considered not significant.

Abbreviations: ns, not significant; AUC, area under the curve.

Table 3 Distribution of melatonin nocturnal peak times in cognitively impaired and cognitively high-functioning participants

Group	Melatonin nocturnal peak time			Total subjects (N)
	12 am	4 am	8 am
Cognitively impaired (n)	11	11	4	26
Cognitively high-functioning (n)	6	16	2	24

Note: The distribution of peak times appears to be phase-advanced toward earlier times for the cognitively impaired group relative to the cognitively high-functioning group, but this pattern was not statistically significant (χ²=2.99, P=0.22).