The descriptive statistics of the total responses (i.e., 121,410 observation-years) along with the minimum and maximum average values across 11 waves are presented in Table 2. The average age across all respondents’ observation-years is 44 years. The number of carers varies from 566 (wave 7) to 989 (wave 12), and they constitute nearly 7 per cent of the total observation-years. Carers’ age ranges from 15 to 92 years with an average age of 52 years across all waves. On an average while a carer spends 14.5 hours a week in care giving activities, a non-carer spends less than an hour (0.38 of an hour with a SD=3.6). In total 42.5 per cent of the respondents are in full-time employment. The alcohol and smoking status reveal 18 per cent of the respondents across all waves are non-drinkers and 81 percent are non-smokers.
Figures 1 and 2 present mean values of carer and non-carer’s health status across the waves by gender. Overall non-carers show better outcomes than carers in all three health measures. Also, non-carers show consistently even and slightly declining trends overtime with males doing better than females in mental health and physical functioning. Whereas carers show fluctuating and slightly decreasing trends over the years in all three health measures with the exception of mental health for males, where we see a slightly increasing trend over the years.
Results of the fully adjusted FE models are presented in Table 3 for both SF36 mental (first three columns) and general health (subsequent three columns). We have not presented the estimates for the SF36 Physical Functioning component in this paper, as our earlier results revealed that the carer status does not influence physical functioning levels (non-significant carer-noncarer difference). In Table 3, the first row presents the impact of Carer Status on mental health and general health outcomes. The following section titled Effects in Non-Carer Group (main terms), presents the estimates of non-carer’s characteristics such as their age and caregiving time and their health behaviours (physical activity level, smoking and drinking level), employment status and level of social engagement. The section titled Carer versus non-carer differences (interaction terms), presents the non-carer and carer differential estimates. Overall the carer status has been interacted with other individual characteristics (such as their age and caregiving time, health behaviours, employment status and level of social engagement) to produce Carer differential effects. There are statistically significant carer-noncarer differences in mental health (estimate (Beta) = -0.587, 95% confidence interval (CI): (-0.972, -0.203), p=0.003) and general health (Beta = -0.670, 95%CI: (-1.058, -0.283), p=0.001). On the other hand, there is no significant carer-noncarer difference in physical functioning scores (presented in Table 4).
Carers show significant disadvantages in both mental and general health outcomes. These carers’ disadvantages remain highly statistically significant (at 1 percent significance level) even after controlling for a range of other household and personal level social, economic, demographic characteristics, addiction and healthy habits in the model (Table 3). Carers report worse mental and general health scores that are on average 3 points less than the non-carers. Additionally, we find for non-carers, the time spent per week in caregiving duties is negatively related to the mental health score but not with general health score. This brings attention to our finding that the negative influence of caregiving is persistence among non-carers even though on average they spend much less time on caregiving than carers (0.38 of an hour compared to 14.5 hours a week). The other confounders in the model, namely, household gross income, any serious personal injury/illness in the past year and time spent per week volunteering/charity work have impact on both mental and general health measures with expected signs in the overall model. These expected effects were statistically significant, except for the time spent in volunteering/charity work.
Figure 3 and 4 present mental and general health marginal means trends respectively, with age (time) for carer and non-carer groups. Both mental and general health scores decreased significantly with age, but at different rates for carers and non-carers. In unadjusted models for mental health, estimates of rates of change were: Beta = -0.054 (95% CI: (-0.084, -0.024), p<0.001) for non-carers; Beta = -0.034 (95% CI: (-0.071, 0.004), p=0.077) for carers, and the difference in rates of change was not statistically significant (p=0.088). For general health, estimates were: Beta = -0.477 (95% CI: (-0.509, -0.443), p<0.001); Beta = -0.437 (95% CI: (-0.477, -0.397), p<0.001), for non-carers and carers respectively, and the difference in slopes was significant (p=0.002). The decreasing patterns remain in fully adjusted models as shown in Table 3. However, for non-carers, the adjusted decrease is non-significant for mental health. Carer status modifies the age effects on mental and general health with low rates of change for carers (moderation effect), although non-significantly for mental health.
As for the employment status, results reveal that non-carers full-time employed persons report both better mental and general health scores compared to part-timers, pensioners, students and housewives. But employment status has no significant modifying effect on carer’s health.
Results for alcohol drinking status when interacted with the number of standard drinks consumed per day revealed that for the non-carers’ group, any level of drinking, compared to those who do not drink, has a negative effect on mental health status with increasing patterns. However, the drinking status exhibits quite an intriguing pattern in term of its effect on non-carer general health status (Table 3, 4th column). For example, if the person is a social drinker and drinks only 2-3 days per month with only 1 to 2 standard drinks or, even 1-2 days per week with 1 to 2 standard drinks then that has a positive effect on general health status compared to those who don’t drink. On the other hand, if the person drinks 5 or more standard drinks for only 2 to 3 days per month or drinks on a weekly basis then that has a negative effect on general health status. The effect modification is significant only in light drinkers (“drink only rarely”, or “drink 2-3 days per month”) who consume 3 to 4 standard drinks for mental health with on average a 2-points high score for carers. The same effect modification is apparent for general health in the same groups as for mental health. However, the 2-points difference on average (in favour of carers) is statistically significant only at 10 percent level.
As expected for the smoking status, results show that, for non-carers, smoking daily has a significant negative effect on their mental health scores, whereas any level of smoking has a negative effect on general health status, increasing with the level of smoking status. For carers, light and medium smoking are more damageable for mental health than daily smoking. This is not the case for general health where the negative effect of smoking gets stronger as the levels of smoking increase. Overall, we have also controlled for the number of cigarettes usually a person smokes per week and found a statistically significant negative effect on the persons’ (irrespective of carer/non-carer status) general health.
As for physical activity status, for non-carers, any level of exercising, compared to those who do not undertake any activity, has a positive and increasing influence on both mental and general health scores, with more activities generating better health outcomes. Carer-noncarer differences in effects appear to be all positive for mental health meaning that physical activities are even more beneficial for carers, but significant only at the physical activity level of 3 times per week.
Similarly, for social interactions and communication with friends and relatives, for non-carers, the more often a person gets together with friends/relatives, compared to infrequent interactions (less often than once in three months), the better mental and general health status they enjoy. However, results show no significant carer-noncarer differences. Carers tend to have better general health scores except those who engage socially every day.
Table 4 presents the base model for SF36 physical functioning component and carer status as an independent variable. There is no evidence of a statistically significant relation between carer status and their physical functioning level and consequently we did not proceed further with this analysis.