Table 4.

Differences in mean telomere length (base pairs) by level of daily caffeine intake for all participants, coffee drinkers only, and adults reporting no coffee intake, after adjusting for the covariates

		Caffeine intake
	Group 0	Group 1	Group 2	Group 3	Group 4
	0 mg	1–149 mg	150–299 mg	300–449 mg	450+ mg
Telomere Length:	Mean + SE	Mean ± SE	Mean ± SE	Mean ± SE	Mean ± SE	F	P
All participants (n = 5826)	5980a + 59	5941a ± 49	5867b ± 57	5850b ± 72	5701c ± 67	6.1	0.0011
(sample size and %)	(862, 12%)	(2796, 44%)	(1248, 23%)	(493, 10%)	(427, 11%)
Coffee drinkers (n = 3024)	—	5862a ± 78	5803a,b ± 70	5764b ± 99	5606c ± 89	5.0	0.0066
(sample size and %)		(1273, 34%)	(937, 32%)	(418, 16%)	(396, 19%)
No coffee intake (n = 2802)	6079a + 67	6046a + 63	5957b + 74	—	—	3.6	0.0398
(sample size and %)	(661, 24%)	(1524, 56%)	(417, 20%)

^a,b,c Telomere means on the same row with the same superscript letter are not significantly different. Means have been adjusted for differences in the covariates, including age, gender, race, education, marital status, housing, BMI, physical activity, coffee intake, alcohol use, and smoking. Under each mean, in parentheses, the unweighted sample size (n) and the survey-weighted proportion of each subgroup are included. Focus should be on the survey-weighted proportions because they represent the U.S. adult population. In adults with no coffee intake, the sample sizes for caffeine Groups 3 and 4 were insufficient for analysis (n = 75 and n = 31, respectively). Therefore, they were merged with Group 2. Including all participants, the mean difference in telomere length between Groups 1 and 2 was borderline significant (P > 0.05 and P < 0.10). Among coffee drinkers only, the difference between Groups 3 and 4 was P = 0.054, and in adults reporting no coffee intake, the difference between Groups 1 and 2 was P = 0.057