3.1. Number of Distinct Trajectories and Weighted Proportions of Sample
The best-fitting model had four trajectories (Figure 1
). All models with more than four trajectories failed to converge. The mean posterior probability of group assignment for all trajectories was high (≥0.94). We labeled the bottom curve (Figure 1
, red line) as “Non/Infrequent (‘Infrequent’) Drinkers
” because women in that group averaged less than 0.1 drink per day in all years.
In contrast, average intake reported by the “Increasing Drinkers” (purple line) climbed monotonically from 0.2 drinks per day in 1998 to 1.4 in 2008. The opposite pattern was observed among the Decreasing Drinkers (blue line) who reported intake levels that declined sharply from 1.8 drinks per day in 1998 to less than 0.1 in 2008. The Stable Drinkers (green line) reported about 1.8 drinks per day through 2004 and then decreased slightly to 1.6 drinks for 2006 and 2008. The model assigned 5.3% of the women to the Increasing Drinkers group, 5.9% to the Decreasing Drinkers group, 24.2% to the Stable Drinkers, and 64.6% to the Infrequent Drinkers group.
When ANOVA methods were used to compare the biannual alcohol use behaviors across these four groups of women, we found that the average numbers of drinks per drinking day and drinks per week differed significantly in all years (p < 0.0001, df = 3, F > 600 in all comparisons). Mean values (normal scale) for drinks per day and drinks per week for all assessment years are shown in Figures 2
, respectively. Findings related to binge drinking were similar (data not shown). The percentage of Increasing Drinkers
who reported binge drinking increased from 0.9% in 1998 to 9.2% in 2008. Corresponding values for the Decreasing Drinkers
were 13.3% and 0.0%, respectively.
These findings are consistent with other research on alcohol use among older women suggesting some women drink moderately for many years, while others gradually reduce their use of alcohol. Previously, we derived 8-year drinking trajectories using National Longitudinal Survey (NLS) data from 1,658 women [12
]. These women, all ages 50–65 in 1995, reported on their recent drinks per day during three or more biannual interviews completed between 1995 and 2003. The best-fitting NLS model also had four trajectories (Increasing Drinkers
–8.8% of the sample, Decreasing Drinkers
–8.6%, Consistent Drinkers
–21.2%, and Non/Infrequent Drinkers
–61.4%). The Wisconsin Longitudinal Study assessed past month drinking behaviors from 3,469 women at age 53 and then reassessed as many as possible at age 64 [35
]. The percentage who were moderate drinkers remained constant at 56%, but the percentage who were non-drinkers increased slightly from 33% to 36% while the percentage of heavy drinkers declined from 11% to 9%. Similarly, a 10-year follow-up assessment on 529 U.S. women ages 55–65 at baseline found the proportion of drinking days per week dropped steadily over time, but many continued to drink several days per week [36
It has been well-established for many years that women can become problem drinkers at any age and may develop alcohol-related problems more rapidly than age-comparable men. However, we believe our analyses are the first to demonstrate that a non-trivial percentage of older women increase their alcohol use over a long time frame. By 2008, the Increasing Drinkers were modestly exceeding the recommended limit of no more than one drink per day, although they averaged only 3.4 drinks per week, which is below the seven drinks per week limit.
The results reported here for older women differ in several respects from the findings that emerged during our parallel research on older men. Among HRS men ages 50–65 in 1998 who also completed at least three biannual interviews with valid alcohol use data in 1998–2008, the best-fitting trajectory based on reported numbers of drinks per day had 5 distinct trajectories. These trajectories were labeled as Non/Infrequent Drinkers
(40.6% of the sample), Increasing Drinkers
(5.5%), Decreasing Drinkers
(7.6%), Moderate Drinkers
(30.7%) and At-risk Drinkers
]. The “at-risk” drinkers averaged more than 3 drinks per day during all years, while the Moderate Drinkers
reported amounts similar to those observed among women in our Stable Drinkers
group (1.6–1.8 drinks per day).
3.2. Risk Factor Analyses
Among the older women in the analyses reported here, chi-square and ANOVA comparisons of baseline characteristics across the four trajectory groups identified many statistically significant differences, although the magnitude of the differences was small in some instances (Table 1
). Mean age ranged from a low of 57.6 years in the Stable Drinkers
to a high of 58.4 years in the Decreasing Drinkers
(p < 0.001). Much larger differences were observed for other variables. For example, the percentages who reported being frequently troubled by pain in 1998 ranged from a low of 19.8% among the Stable Drinkers
to a high of 34.1% among the Infrequent Drinkers
(p < 0.001). The drinking trajectory groups did not differ significantly on the mean number of interviews completed during our study interval. Overall, 68.6% of the women completed 5 or all 6 of the study interviews.
Using all 1998 demographic, health, and alcohol/tobacco use characteristics in Table 1
and the base-year sampling weights, we constructed two adjusted logistic regression models. Model 1 compared the 232 Increasing Drinkers
(purple line in Figure 1
) who averaged 0.2 drinks per day in 1998 to the 2,867 Infrequent Drinkers
(red line) who averaged <0.1 drinks per day. On a multiplicative scale, this difference is notable, but the absolute difference is small. Model 2 compared the 264 Decreasing Drinkers
(blue line) to the 1,076 Stable Drinkers
(green line). Both of these groups averaged 1.8 drinks per day in 1998.
Model 1 results (Table 2
) suggest infrequent drinkers in 1998 who increased the amount of alcohol consumed over the next 10 years were more likely than those who continued as non/infrequent drinkers to have more education (AOR = 1.59, 95%CI: 1.19–2.11), engage in vigorous physical activity (1.41, 1.06–1.86), and report that they had recently consumed 4 or more drinks on one occasion (4.34, 1.07–17.59). However, it is important to note that at baseline, binging was rarely reported in either group (Increasing drinkers
: 0.9%, Infrequent Drinkers
: 0.2%). The Increasing Drinkers
were less likely to be obese in 1998 (0.59, 0.42–0.84) or report current smoking (0.67, 0.47–0.94).
Women who reported drinking more than one drink per day in 1998 but then steadily decreased their intake during follow-up were more likely than those who continued as stable drinkers (Table 2
, Model 2) to report depression (AOR = 2.16, 95%CI: 1.29–3.61) and cigarette smoking (1.50, 1.05–2.15). Problem drinking is well-established as a risk factor for depression and depressed individuals are routinely advised to limit their intake of alcohol [37
]. They were less likely to be retired (0.63, 0.41–0.98) or report recently drinking 4 or more drinks on one occasion (0.40, 0.25–0.61).
The results observed for education, retirement, and recent binge drinking were expected, but the magnitude of the AORs associated with consuming four or more drinks on one occasion was striking. Infrequent drinkers at baseline who reported drinking this heavily at least once in the last three months were four times more likely to report higher levels of drinking on subsequent interviews. Conversely, stable drinkers who reported any binge drinking were far less likely to sharply reduce their alcohol intake over follow-up. Because recent binging at baseline was positively associated with a CAGE score ≥ 2 (X2 = 138.6, p < 0.0001), we expect that a few Increasing Drinkers who were abstinent at baseline may be women with a history of alcohol problems who resumed drinking after the 1998 interview.
The finding that Increasing Drinkers
were more likely to report vigorous exercise in 1998 is consistent with a small body of recent studies showing a strong positive, but not necessarily causal, correlation between physical activity and alcohol use [38
]. The observations that Increasing Drinkers
were more likely to report exercise, less likely to be obese, and less likely to smoke may all reflect an underlying association between health behavior or lifestyle and alcohol use. The associations are not paradoxical, because many older women know that moderate alcohol use provides important health benefits and may choose to drink for that reason. The adjusted odds ratios for these variables in Model 2, although not statistically significant, were also consistent with a positive correlation between other health behaviors and drinking. A cross-sectional study of alcohol use among 6,917 Swedish women ages 50–59 similarly found that nondrinkers had poorer health and more physical symptoms than weekly drinkers [39
]. Others have also found a faster decline in alcohol consumption among older adults who smoke [40
We searched the literature for comparable longitudinally-based, alcohol-related risk factor analyses specific to older women and were unable to find appropriate comparison studies. Adjusted logistic regression models were not derived for the NLS data mentioned above due to the smaller size of the sample (1,658 women versus
the 4,439 in the HRS) and the termination of NLS data collection in 2003. In our analyses of risk factors among HRS men, Increasing Drinkers
were also more likely to report vigorous exercise and less likely to report smoking. Decreasing Drinkers
were also less likely to report binge drinking [16
]. Other results were dissimiliar.