A total of 7834 participants had complete data at baseline, reducing to 6785 (Phase 4), 6262 (Phase 5), 5917 (Phase 6) and 5926 (76% of original at Phase 7). In univariate analyses (), PCS and MCS scores were lower for those living in more deprived or more socially fragmented neighbourhoods. PCS scores were higher and MCS scores were lower for younger participants.
Description of study cohort and mean (standard error) SF-36 scores at baseline (Phase 3, 1991–93) and 10 year follow-up (Phase 7, 2002–04)
Analysis of movers and non-movers combined
PCS declined at a rate of 2.7 units for each 10 years of follow up (). shows significant variation in PCS scores between neighbourhoods, between individuals and within individuals. The variation in average PCS between neighbourhoods was small in magnitude (1.241) compared with variation within neighbourhoods (40.270 and 28.842). There was no evidence that the change in PCS over time (i.e. the slope) varies across neighbourhoods. However, there was evidence that the slope varied across individuals. This could be interpreted as evidence that the ageing process is heterogeneous across individuals although this is not the focus of the present study. On average, small improvements in MCS scores were seen over time at a rate of ~1.0 unit every 10 years. There was significant variation in MCS scores between neighbourhoods which, as for PCS scores, was small in magnitude compared with the variation within neighbourhoods. The change in MCS over time also varied across neighbourhoods (shown by variation in slope of 0.010 and SE 0.005). The covariance between the intercept and slope was positive (0.088 from ), indicating that neighbourhoods with high initial levels of PCS saw greater improvements in PCS over time. In other words, there was a fanning out of PCS scores across neighbourhoods over time.
Variation in SF-36 PCS and MCS scores within and between neighbourhoods from the base model (including intercept and length of follow-up as fixed and random parameters and no other covariates)
summarizes the full models for physical component scores which add neighbourhood and individual fixed effects. Each one standard deviation increase in Townsend deprivation score was associated with a drop in PCS score of 0.311 points (P < 0.001) (Model 1). The relationship between PCS score and time did not differ by Townsend deprivation. In other words, the time-Townsend interaction term was not statistically significant. Social fragmentation was not associated with PCS scores (Model 2). Older people and those in lower socioeconomic positions had lower PCS scores compared with older and more advantaged participants and they also experienced greater declines in PCS over time. Trajectories did not differ for men and women so a gender by time interaction was not included. No significant variation between neighbourhoods remained.
Neighbourhood characteristics and SF-36 PCS scores
Each 1 SD increase in Townsend deprivation score was associated with a drop in MCS score of 0.5 points (P < 0.001) (, Model 1). Although there was a suggestion that this effect got larger over time, the Townsend-time interaction term was not statistically significant [estimate (SE) −0.014 (0.010)]. Social fragmentation was also associated with MCS scores but trajectories did not differ by social fragmentation (Model 2, ). MCS scores increased over time and older cohorts saw higher initial scores and greater increases over time. Those in lower socioeconomic positions had lower MCS scores and these socioeconomic differences widened over time. After adjustment for individual and neighbourhood characteristics, variation in the intercept and slope of MCS was of borderline statistical significance.
Neighbourhood characteristics and SF-36 MCS scores
Analysis of non-movers only
When analyses were confined to participants who were still in the same neighbourhood after 10 years of follow-up, the regression estimates for associations between PCS and neighbourhood deprivation and social fragmentation were a little larger in magnitude [−0.445 (SE 0.116) and −0.228 (0.113) per 1 SD increase, respectively]. Estimates of the associations between MCS and both deprivation and social fragmentation were similar to those for the full dataset [−0.457 (SE 0.125) and −0.458 (0.123), respectively] and terms representing the interaction between these neighbourhood characteristics and time indicated significant widening over time [−0.028 (SE 0.014) and −0.037 (0.013), respectively] ().
Figure 1 Mean predicted SF-36 PCS scores (upper graphs) and MCS scores (lower graphs) for Whitehall II participants through years of follow up by level of neighbourhood deprivation and social fragmentation. Data correspond to all participants living in the same (more ...)
Analysis of participants who were illness-free at baseline
summarizes the associations between neighbourhood characteristics and functioning for those who reported no long-term illness at baseline. Neither neighbourhood characteristic was associated with PCS score among those who were free of long-term illness at baseline. However, neighbourhood deprivation and social fragmentation remained significantly associated with initial MCS scores for participants who were illness-free at baseline.
Neighbourhood characteristics and SF-36 scores for participants with and without long-term illness at baseline